KR100360182B1 - Method of Biotreatment for Solid Materials In A Nonstirred Surface Bioreactor - Google Patents

Abstract

Methods of biotreatment of solid materials are provided for the removal of unwanted compounds using comparative surface bioreactors. According to the method, the surfaces of the plurality of coarse substrates are coated with a solid material to be biotreated to produce a plurality of coated coarse substrates. The coarse substrate has a particle size greater than about 0.3 cm and the solid material to be biotreated has a particle size of less than about 250 μm. Subsequently, a plurality of coated coarse substrates are stacked in the bottom or a plurality of coated substrates are placed in a tank to form a counter surface reactor so that the empty space of the reactor is at least about 25%. The reactor is inoculated with microorganisms capable of degrading unwanted compounds in the solid material and then the biomass is biotreated in a surface bioreactor until the unwanted compounds in the solid material decompose to the desired concentration. This method is useful for biotreatment of contaminated soils, desulfurization of coal and biooxidation of refractory sulfide ores and concentrates.

Description

Method of Biotreatment for Solid Materials In A Nonstirred Surface Bioreactor

Background of the Invention

Biological treatment methods are being explored throughout the industry. Such methods have been used for wastewater treatment, hazardous waste removal, desulfurization of coal and biooxidation of refractory sulfide ores.

Various methods can be used for the biotreatment of solid materials, including in situ treatment, landfarming, composting, heap treatment, and stirred or stirred tanks. Several bioreactors have been used for the biotreatment of solid materials for in vitro biotreatment. A bioreactor may be defined as a container or a reactant in which a reaction is performed by a microorganism included in the biological reactor itself or an enzyme produced by the microorganism. The main goal in the design of bioreactors is to create an optimal environment in which the desired biological process takes place on a large and economic scale.

When biotreating a solid material, the desired biological reaction typically involves the direct or indirect decomposition of some unwanted compounds present in the solid material. To do this economically, the bioreactor must lower the concentration of the unwanted compound to an acceptable level in the acceptable amount (flow) of solid material to be treated.

In general, biotreatment is slow, and in aerobic methods, aerobic microorganism (s) require large amounts of oxygen to directly or indirectly metabolize unwanted compounds. Thus, a representative major problem for most aerobic biotreatment methods used is oxygen delivery. Recent aerobic bioreactors not only ensure that the microorganisms in use have access to the material to be biooxidized or metabolized, but also maintain the correct pH and temperature to allow the biological process to proceed throughout the bioreactor, as well as proper oxygen and It is designed to supply nutrients.

Stirred tank bioreactors are used in many types of aerobic biological processes, including the biooxidation of refractory sulfide gold ores and the bioremediation of contaminated soils. Stirred tank bioreactors have a very good contact between the bioleach and the solid material to be treated. In addition, the stirred tank method is typically in good oxygen because it sparges air or oxygen into the tank. However, even in stirred tank bioreactors where oxygen is supplied by air or oxygen sparging, the low solubility of oxygen in water (10 ppm) requires a wide contact surface for gas and water contact. This is usually achieved through impellers and significant energy consumption. Because of the high energy costs of agitating and oxygenating the reactor, this type of bioreactor is mainly used in bioprocesses that reach a desired target point relatively quickly, usually within a week. For slower biological reactions, large, generally static, batch batches with the lowest energy costs are the best solution. However, the goal of providing an optimal environment for bacteria or other microorganisms is still the most important.

There are three main types of static batch bioreactors used to biotreat soils contaminated with toxic organic compounds. One of these is land farming. This is a treatment to improve contaminated soil in large open spaces. Typically, the soil is laid over a high density polyurethane boundary area covered with sand for drainage. Air can be supplied through the perforations and by changing the land once or twice a week. This method has been widely used where contaminated with polynuclear aromatics (PNA) and pentachlorophenol (PCP). One limitation of this method is that large areas are required because the soil must be relatively thin to allow adequate airflow. This method also requires plowing the ground and restricts airflow if the soil layers are too thick or not very well mixed.

Another technique used in the biological treatment of contaminated soil is composting. Compost is made from contaminated soil and various supplements necessary for continuous composting, such as wood chips, straw or fertilizer. These supplements increase the amount of biodegradable organics, reduce bulk weight and increase air voids to structurally improve the compost layer and increase the amount of inorganic nutrients in the mixture. Composting can be carried out using air pipes or in unfolded sediments that grind the ground or artificially maintain the air stream. One disadvantage of the addition of organic supplements is that biodegradation of the supplements generates heat and requires oxygen. Composting is usually done batchwise, and part of the compost is used to inoculate the next compost. This method has been effectively used for many types of organic contaminants including diesel fuel, 2,4,6-trinitrotoluene (TNT), polyaromatic hydrocarbons (PAH), benzene, and xylene.

Bottom biotreatment is another static bioprocess used in the biotreatment of excavated contaminated soils. In this way, the soil is piled up with 2.4-3.7 m high sediment over the border area. Air can be supplied to the porous tube to improve air flow. In this case, the perforated tubes are placed at regular intervals on about 31 cm of soil plate. The gravel layer is then covered over the perforated tube, usually to protect the perforated tube from heavy installations. The excavated soil is then stacked on the gravel as sediments of 2.4-3.7 m high. Maintain moisture using an irrigation system. Fertilizers or lime may be used to adjust the pH of the soil, and sand may be used to increase porosity. This method is low cost and can be used for slow biological processes. However, this method can be too slow if the soil is squeezed during or after depositing the heap and the heap is limited by the air supply.

Thus, contact of air and liquids remains an important rate limiting factor in current static bioprocesses used for soil treatment such as bottom sediment biotreatment, composting and land farming. Current methods improve air flow to the extent possible by changing batch soil or supplying air through a porous air pipe. However, any pressure on the air flow in the bioreactor will hamper the efficiency of the process. In addition, if the contaminated soil is not partially exposed to bacteria or other nutrients, including oxygen, the entire bioprocess will be slow or not perform perfectly. Similarly, in the case of bottom biooxidation of coal and refractory sulfide gold ores, the biooxidation of sulfides is effectively performed by bacteria only when metal sulfides are exposed to bacteria, water, nutrients and air. If sulphide is buried in solid pieces of ore or coal, biooxidation will not occur. In addition, if air or liquid flow in the hips is limited, biooxidation will also be limited. As a result, there is a need for an improved bioreactor design that enables biotreatment of solid materials with improved air and fluid flow throughout the bioreactor and the solid materials being treated.

The use of eosinophilic, autotrophic bacteria to biooxidize sulfide minerals in refractory sulfide ores is one biotreatment method that has been particularly active in the last 10 to 20 years.

Gold is one of the rare metals on the planet. Gold ores can be divided into two types: ores that are easy to mill and refractory ores. Ore that is easy to mill can be processed by simple gravity or direct cyanation. On the other hand, refractory ores cannot be processed by conventional cyanation treatment. In the case where gold is not sufficiently dissolved in the conventional cyanide leaching technique and cannot be economically processed, the gold-containing burial ore is considered to be fire resistant. Such ores are often refractory because they contain excessive amounts of metal sulfides (eg pyrite and pyrite) and / or organic carbonaceous materials.

Many refractory ores consist of ores containing precious metals such as gold embedded in iron sulfide particles or other metal sulfide particles. Iron sulfide particles consist mainly of pyrite and nonferrite. Precious metals are often occluded in sulfide minerals. For example, gold is usually present as microscopic particles finely dispersed in refractory sulfide masses of pyrite or pyrite. If gold or other precious metals remain occluded in the sulfide mass after grinding, the sulfides must be oxidized to release the enclosed precious metals and to be treated with leaching agents (or eluents). Reduces fire resistance.

Many methods for oxidizing sulfide minerals to liberate precious metals are well known in the art. This method can generally be divided into two types: milling and heaping. Milling operations are typically expensive methods with high implementation and capital costs. As a result, milling operations are not applicable to low grade ores with gold concentrations of less than approximately 2.4 g / ton, although typically the total recovery is higher for milling methods. Milling operations are much less useful for ores with gold concentrations as low as 0.68 g / ton.

Two known methods of oxidizing sulfides in milling operations are pressurized oxidation and roasting in an autoclave.

Oxidation of sulfides in refractory sulfide ores is also characterized by eosinophilic autotrophic microorganisms such as Thiobacillus ferrooxidans , Sulfolobus , Acidianus species, and facultative thermophilic bacteria. By microbial pretreatment. These microorganisms utilize the oxidation of sulfide minerals as an energy source during metabolism. During the oxidation process, the microorganisms oxidize iron sulfide particles to solubilize iron with ferric sulfide with sulfate ions.

If the refractory ore to be processed is a carbonaceous sulfide ore, after microbial pretreatment to prevent preg-robbing of gold cyanide complexes or other noble metal-leaching agent complexes by the original carbonaceous material upon treatment with the leaching agent Additional processing steps may be necessary.

As used herein, sulfide ores or refractory sulfide ores will be understood to encompass refractory carbonaceous sulfide ores.

Known bioleaching methods of carbonaceous sulfide ores are disclosed in US Pat. No. 4,729,788, issued March 8, 1988, which is incorporated herein by reference. According to the disclosed method, thermophilic bacteria such as sulfolobus and thermophilic bacteria are used to oxidize the sulfide component of the ore. The bioleached ore is then treated with a blanking agent to suppress the pregrating tendency of the carbonaceous component of the ore. The precious metal is then extracted from the ore using conventional leaching cyanide or thiourea.

Another known method for bioleaching carbonaceous sulfide ores is disclosed in US Pat. No. 5,127,942, issued July 7, 1992. According to this method, the ore is oxidative bioleached to oxidize the sulfide component of the ore and to liberate precious metals. The ore is then inoculated with a bacterial combination characterized by inactivating the pregrating tendency of the carbonaceous material in the ore with the nutrients for the bacteria to promote the growth of the bacterial combination. That is, the bacterial combination functions as a biological blanking agent. Precious Metals Adsorption Treatment with a microbial combination capable of inactivating carbon is followed by leaching the ore with a suitable leaching agent to dissolve the precious metal in the ore.

Oxidation of refractory sulfide ores using microorganisms, also referred to as biooxidation, can be carried out by milling or heaping methods. Compared to pressurized oxidation and roasting, the biooxidation method is simple to operate, requires less capital, and costs less operation. In practice, biooxidation is often chosen as a method for oxidizing sulfide minerals in refractory sulfide metals because it is economically advantageous over other means of oxidizing ores. However, due to the slower rate of oxidation due to microorganisms compared to chemical and mechanical means of oxidizing refractory sulfide ores, biooxidation is often a limiting step in the mining process.

One milling type biooxidation method involves grinding ore and then treating the slurry of ore in a stirred bioreactor in which microorganisms can use finely divided sulfides as energy sources. This milling method was used on a commercial scale in the Tonkin Springs mine. However, in the mining industry, it is generally believed that the Tonkin Springs biooxidation work failed. The second milling type biooxidation method involves separating noble metal containing sulfides from minerals using conventional sulfide concentration techniques such as flotation, and then oxidizing the sulfides in a stirred bioreactor to mitigate their fire resistance. This type of commercial work is used in Africa, South America and Australia.

Biooxidation in the heap process typically involves forming a heap with pulverized refractory sulfide ore particles and then inoculating the heap with a microorganism capable of biooxidizing the sulfide mineral in the ore. After biooxidation reached the desired target point, the hips were drained and washed repeatedly. The free precious metals can then be leached with a suitable leaching agent.

Typically, precious metal containing ores are leached with cyanide, which is the most effective leaching agent or eluent for recovering precious metals from the ore. However, when cyanide is used as a leaching agent, the heap must first be neutralized.

Since cyanide treatment must be performed at high basic pH, while biooxidation occurs at low acidic pH, bottom biooxidation with conventional cyanide treatment is essentially a two step process. As a result, if the treatment method uses heap biooxidation, the process must be separated in two steps. This is usually done by dividing the steps temporarily. For example, in the heap biooxidation process of refractory sulfide gold ores, the heap is first biooxidized and then washed, neutralized and treated with cyanide. To accomplish this economically and practically, most hip biooxidation operations use permanent pads on one of several ores arranged or unarranged.

Among the many biooxidation methods available, bottom biooxidation is at the lowest cost of operation and capital. Thus, the bottom biooxidation method is particularly applicable to low or waste type ores, ie ores with a concentration of less than about 2.4 g / ton of gold (or equivalent precious metals). However, bottom biooxidation is very slow compared to milling biooxidation methods. Bottom biooxidation typically takes several months to fully oxidize sulfide minerals in ore to recover gold or other precious metals in sufficient amounts through cyanide leaching, which is an economical method involved. Bottom biooxidation operations are therefore limited by the length of time required for sufficient biooxidation to occur in order to enable economic recovery of gold. The longer the time required for biooxidation, the larger the permanent pad installation and the greater the capital investment required. In mines with limited land area suitable for bottom pad structures, the size of the permanent pads is a limiting factor in the amount of ore processed in the mines, and therefore in a mine. In such circumstances, the rate limiting factor of the biooxidation process becomes more important.

Rate limiting factors for the bottom biooxidation method include inoculum access, nutrient access, air or oxygen access, toxin accumulation and carbon dioxide access, which are necessary to make the process more efficient and in good treatment conditions. Moreover, in biooxidation, variables such as accessibility, particle size, settling, density, etc., cannot be economically restored once the heap has been produced, thus inducing time, growth cycle, and fat associated with the biooxidant. Biologic activity and bacterial viability are important considerations. This is because once the heap is formed, it can only be repaired on a limited basis.

Ore with high clay and / or fine content is a particular problem when processed by bottom leaching or bottom biooxidation methods. The reason is that clay and / or granules can move through the plug and channels of the bottom and air and liquid flows, creating mud, bone, lack of nutrients, lack of carbon dioxide or oxygen, and uneven distribution of biooxidants. Is the point. As a result, a large area of the bottom can be blocked and inefficiently leached. This is a common problem in cyanide leaching, leading to a particle agglomeration process using polymers for low pH bioleaching and cement for high pH cyanide leaching. Polymer flocculation aids can also be used in high pH environments and are commonly used for noble metal leaching after oxidative bioleaching of iron sulfides in ores.

Biooxidation of refractory sulfide ores is particularly sensitive to porous channels blocked by scattered clay and granular material because bacteria require large amounts of air or oxygen to biooxidize and multiply iron sulfide particles in the ore. The flow of air is also important for dissipating the heat generated by exothermic biooxidation reactions because it can kill bacteria that grow in large, poorly ventilated heaps due to overheating.

US Patent No. 5,246,486, issued September 21, 1993 to William Kohr, and US Pat. No. 5,431,717, issued July 11, 1995, incorporated by reference herein, provides good fluid flow. It is about increasing the efficiency of the hip biooxidation process by ensuring (both gas and liquid) throughout the heap.

Ore with low sulphide or pyrite or high with acid consuming substances such as calcium carbonate or other carbonates can also be a problem when treated in bottom biooxidation. The reason is that the acids produced by these low pyrite ores are insufficient to maintain the low pH and high iron concentrations necessary for bacterial growth.

Solution listing and control also provides rate limiting considerations that are important to the bottom biooxidation method. The solution discharged from the biooxidation heap will be acidic and will contain bacteria and ferric ions. This solution can thus be used advantageously by flocculation of fresh ores or by recycling to the upper layer of the heap. However, toxic and inhibitory substances may arise from this discharge solution. For example, ferric iron ions, which are generally useful aids in pyrite leaching, interfere with bacterial growth when their concentration exceeds about 30 g / l. Other metals that slow down the biooxidation process may also be in this solution. Such metals that can often be found in refractory sulfide ores include arsenic, antimony, cadmium, lead, mercury and molybdenum. Other toxic metals, biooxidation by-products, dissolved salts, and materials produced by bacteria can also interfere with the rate of biooxidation. If these inhibitors occur at a sufficient level in this effluent solution, reuse of this effluent solution will be detrimental to the rate at which the biooxidation process proceeds. In fact, continued reuse of the effluent solution with sufficient interfering substances will disrupt the biooxidation process.

The method disclosed in US patent application Ser. No. 08 / 329,002, filed Oct. 25, 1994 to Core et al., Which is incorporated herein by reference, teaches a method of treating a bioleaching solution to minimize the production of inhibitory substances. have. As a result, if the bioleached effluent solution is recycled to the heap top, the rate of biooxidation in the heap will not be slowed or will be slower than if recycled without treating the drained solution.

While the method improves the speed at which the bottom biooxidation process proceeds, the bottom biooxidation will still take much longer than milling bioreactor methods such as stirred bioreactors. As pointed out above, agitated bioreactors for lower refractory sulfide ores are not practical alternatives due to their high initial capital costs and high operating costs.

Accordingly, there is a need for a heap bioleaching method that can be used to biooxidize precious metal containing refractory sulfide ores and has improved air and fluid flow in the heap. There is also a need for a heap bioleaching method capable of treating ores with low content of sulfide minerals or ores with high content of acid consuming materials such as calcium carbonate.

There is also a need for biooxidation methods that can be used to liberate precious metals occupied in concentrates of refractory sulfide minerals. Milling methods currently used to oxidize such concentrates include bioleaching in stirred reactors, pressurized oxidation in autoclaves and roasting. This milling method releases captured precious metal by oxidizing sulfide minerals in the concentrate relatively quickly. However, if the concentrate does not contain high concentrations of gold, it is not economical because of the capital or high operating costs of these methods. And, the milling bioleaching method is the lowest in terms of both initial capital and operating costs, but is still not suitable for processing concentrates containing less than about 17 g of gold per tonne of concentrate, typically about 2.4 per tonne Requires ore with a gold concentration of at least g. Accordingly, there is a need for a method that can be used to biooxidize concentrates of noble metal containing refractory sulfide minerals at a rate comparable to that of stirred tank bioreactors, but which has a capital and operating cost comparable to that of the bottom bioleaching process.

In addition to concentrates of noble metal containing sulfide minerals, there are many sulfide ores containing metal sulfide minerals that can potentially be treated using biooxidation methods. For example, many copper ores include copper sulfide minerals. Other examples are zinc ores, nickel ores and uranium ores. Biooxidation can be used to dissolve useful metals such as copper, zinc, nickel and uranium from concentrates of these ores. The dissolved useful metals can then be recovered using known techniques such as solvent extraction, iron cementation and precipitation. However, due to the small volume of sulfide concentrates produced from sulfide ores, stirred bioreactors can be incredibly expensive, and standard hip operations are not economically easy because they take a long time to recover useful metals. Therefore, there is also a need for an economic method of biooxidizing a concentrate of metal sulfide minerals made from sulfide ores to dissolve the useful metals so that the useful metals can be recovered from the bioleaching solution in the next step.

Thus, there is a need for biooxidation methods that can be used to treat sulfide concentrates obtained from refractory sulfide ores, which are much faster than the current bottom biooxidation methods, but with lower initial capital and operating costs than stirred bioreactors. This demand has not been met to date. There is also a need for a biooxidation method that can be used to economically treat sulfide concentrates of metal sulfide-type ores, but this requirement has also not been achieved.

Summary of the Invention

The present invention relates to the biotreatment of solid materials in a control panel bioreactor. To this end, in a first aspect of the present invention, a method is provided for removing unwanted compounds by biotreating solid materials using a non-surface surface bioreactor. According to the method of the present invention, the surface of the plurality of coarse substrates is coated with a solid material to be biotreated to produce a plurality of coated coarse substrates. The control surface reactor is then stacked with a plurality of coated coarse substrates in a heap or a plurality of coated substrates are placed in a tank to form a control surface surface reactor so that the empty space of the reactor is at least about 25%. The reactor is inoculated with microorganisms capable of degrading unwanted compounds in the solid material and then the biomass is biotreated in a surface bioreactor until the unwanted compounds in the solid material decompose to the desired concentration. In order to ensure adequate space in the bioreactor, the coarse substrate preferably has a particle size of at least about 0.3 cm and the solid material to be biotreated preferably has a particle size of less than about 250 μm. The thickness of the solid material coated on the plurality of coarse substrates is preferably such that the microorganisms used in the biotreatment are less than about 1 mm in order to properly access all the solid materials to be biotreated. Thicker coatings increase the capacity of the bioreactor, but the microorganisms used will have limited access to the underlying particles of the solid material, which will slow down the biotreatment process. In order for the microorganisms to properly access and fully utilize the capacity of the bioreactor, the thickness of the solid material coating should be at least about 0.5 mm and less than about 1 mm. To improve air and liquid access, the empty space of the bioreactor can be set to at least about 35%. This will greatly speed up the progress of bioprocessing methods.

Various materials can be used as coarse substrates, including rocks, gravel, volcanic rocks, carbonate mineral containing rocks, bricks, concrete blocks, slags and plastics.

The method according to the first aspect of the present invention is useful for many different biotreatment methods, including biotreatment of contaminated soil, desulfurization of coal and biooxidation of refractory sulfide ores. In biological treatment applications, unwanted compounds are usually organic compounds. Undesired compounds in coal desulfurization and refractory sulfide ore biooxidation applications are sulfide minerals.

In a second aspect of the present invention, there is provided a method of biooxidizing a sulfide mineral concentrate consisting of fine metal sulfide particles using a comparative surface bioreactor to liberate desired useful metals. This method includes coating a concentrate of metal sulfide particles over a number of coarse substrates, such as coarse particles, volcanic rocks, gravel, or rocks containing carbonate minerals as a source of CO ₂ for bacteria. After metal sulfide particles are coated or spread over a plurality of substrates, the coated substrates are deposited with a heap or the coated substrates are placed in a tank to form a counter surface reactor. The metal sulfide particles on the surface of the plurality of coated substrates are then biooxidized to release their useful metals.

Depending on which ore deposits are mined, the sulfide mineral concentrates used in the present invention include sulfide concentrates obtained from precious metal containing refractory sulfide ores or base metal sulfide types such as chalcopyrite, acicular nickel or zinc ore. Sulfide concentrates obtained from ore. The former is different in that the desired metal is a precious metal occluded in the sulfide mineral, the latter is a nonmetal such as copper, nickel or zinc and is present as a metal sulfide in the sulfide concentrate.

In a third aspect of the present invention there is provided a method for recovering precious metals from a precious metal containing refractory sulfide ore using a comparative surface bioreactor. The process according to this aspect of the invention comprises the steps of preparing a sulfide mineral concentrate consisting of fine metal sulfide particles obtained from refractory sulfide ores, coating a surface of a plurality of coarse substrates using a concentrate of metal sulfide particles, a plurality of coated Forming a hip using a substrate and biooxidizing the metal sulfide particles on the surface of the plurality of substrates, contacting the biooxidized metal sulfide particles with a noble metal leaching agent to dissolve the precious metals from the biooxidized metal sulfide particles, and the precious metals Recovering from the leach agent.

According to a fourth aspect of the present invention, there is provided a method for recovering noble metals from a noble metal containing refractory sulfide ore using a comparative surface bioreactor. The process according to this aspect of the invention comprises the steps of preparing a sulfide mineral concentrate consisting of fine metal sulfide particles obtained from a noble metal containing refractory sulfide ore, coating the surface of the plurality of coarse substrates with metal sulfide particles, and a plurality of coated substrates. Into the tank, biooxidizing the metal sulfide particles on the surface of the plurality of coarse substrates, contacting the biooxidized metal sulfide particles with the noble metal leaching agent to dissolve the precious metals from the biooxidized metal sulfide particles, and From the recovery of precious metals.

According to a fifth aspect of the invention, there is provided a method for recovering precious metals from sulfide mineral ores using a comparative surface bioreactor. The method according to this aspect of the invention comprises the steps of preparing a fine metal sulfide particle sulfide mineral concentrate obtained from a sulfide mineral ore, coating the surfaces of the plurality of coarse substrates with a metal sulfide particle concentrate, Laminating with a heap or placing a plurality of coated substrates in a tank, biooxidizing metal sulfide particles on the surface of the plurality of coarse substrates to produce a bioleached solution, dissolving a metal portion of the metal sulfide particles, And recovering the desired useful metals from the bioleachate effluent solution. Ore of particular interest that can be processed in this way includes sulfide ores of copper, zinc, nickel, molybdenum, cobalt and uranium.

In a sixth aspect of the present invention there is provided a method for dispensing a concentrate of fine refractory sulfide minerals onto a heap of coarse support material selected from the group consisting of volcanic rock, gravel, carbonate minerals, bricks, concrete blocks and slag. (B) biooxidizing the concentrate of the refractory sulfide mineral, (c) leaching the precious metals from the biooxidized refractory sulfide mineral using a leaching agent, and (d) recovering the precious metals from the leaching agent. A method of recovering noble metals from a concentrate consisting of fine refractory sulfide mineral particles containing noble metals is provided. The advantage of this method is that the oxidation rate of sulfide minerals is much faster than that observed in traditional bottom bioleaching operations. However, despite this high biooxidation rate, the initial capital and operating costs of the disclosed methods are lower than the associated milled biooxidation methods.

Gold is the preferred precious metal recovered using the process according to this aspect of the invention. However, other precious metals, including silver and platinum, can also be recovered. Volcanic rock is a particularly preferred substrate material because of its large surface area. As will be appreciated by those skilled in the art, various leaching agents may be used in combination with the methods of the present invention, but thiourea and cyanide are preferred, in particular cyanide being the preferred leaching agent.

In a seventh aspect of the present invention there is provided a coarse selected from the group consisting of: (a) forming a sulfide mineral concentrate consisting of fine metal sulfide particles, (b) waste rock containing volcanic rock, gravel, carbonate minerals, bricks, concrete blocks and slag Dispensing the concentrate onto the bottom of the support material, (c) biooxidizing the concentrate, and (d) recovering the useful metals from the solution used to biooxidize the metal sulfide minerals. A recovery method is provided. Sulfide ores that can be processed using the method of the present invention include, for example, chalcopyrite, zinc zinc, nickel sulfide ore and uranium sulfide ore. Due to the fact that this method uses a heap of support material as the bioreactor, its capital and operating costs are lower than milling bioleaching operations. However, due to good air flow at the bottom, the biooxidation rate of sulfide minerals is very high and can reach speeds in milling operations. Depending on the sulfide ore from which the concentrate is obtained, useful metals that can be recovered from the process according to this aspect of the invention include copper, zinc, nickel and uranium. The support material used in the present invention is preferably volcanic rock with a large surface area.

The above and other objects, features and advantages will be apparent to those skilled in the art from the following description of the preferred embodiments.

The present invention relates to a method for the biotreatment of solid materials. In particular, the present invention relates to an ex situ biotreatment method of a solid material by an aerobic method of decomposing unwanted compounds present in the solid material.

1 is a schematic diagram of a process flow diagram in accordance with one embodiment of the present invention.

2 is a cross-sectional view of a refractory sulfide ore substrate coated with a concentrate of metal sulfide particles according to the present invention.

3 is a schematic diagram of a process flow diagram in accordance with another embodiment of the present invention.

4 is a schematic diagram of a process flow diagram in accordance with another embodiment of the present invention.

5 is a schematic diagram of a process flow diagram in accordance with another embodiment of the present invention.

6 is a graph showing the percentage of iron oxidation versus time for all ores compared to the method according to the invention.

7 is a graph comparing the daily average biooxidation rate of all ores with that of the method according to the invention.

8 is a graph showing the percentage of biooxidation in another method according to the present invention.

9 is a graph showing the daily average biooxidation rate in the method corresponding to FIG. 8.

FIG. 10 is a graph showing the percentage of biooxidation over time for pyrite concentrate coated on waste rock support and the same pyrite concentrate coated on refractory sulfide mineral support containing high concentration of mineral carbonate.

FIG. 11 is a graph depicting biooxidation rates for concentrates distributed on top of a stirred tank type method versus a volcanic rock bottom method according to an embodiment of the present invention.

A first embodiment of the present invention is described to biotreat a solid material in a non-surface surface bioreactor to remove unwanted compounds. According to a first embodiment, the surfaces of a plurality of coarse substrates having a particle size of about 0.3 cm or more are coated with a solid material to be biotreated to form a plurality of coated coarse substrates. The particle size of the solid material to be biotreated is less than about 250 μm to form a very uniform coating on the coarse substrate. A plurality of coated coarse substrates are stacked on the bottom or a plurality of coated coarse substrates are placed in a tank to form a counter surface reactor so that the empty space of the reactor is at least about 25%. The reactor is inoculated with microorganisms capable of degrading unwanted compounds in the solid material and biotreated in a surface bioreactor until the unwanted compounds in the solid material decompose to the desired concentration.

This biotreatment method can be used for biotreatment of contaminated soil, desulfurization of coal and biooxidation of refractory sulfide ores, to name just a few. In biological treatment, the solid material is usually soil and the unwanted compound is usually an organic compound in the soil. Therefore, the present invention is applied to a number of places worth the investment. Examples of organic pollutants that can be removed from the soil using the present invention include waste oil, grease, jet fuel, diesel fuel, crude oil, benzene, toluene, ethylbenzene, xylene, polyaromatic hydrocarbons (PAH), polynuclear aromatics (PNAs) , Pentachlorophenol (PCP), polychlorinated biphenyls (PCBs), creosote, pesticides, 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-tri Azine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocin (HMX), N-methyl-N-2,4,6-tetranitroaniline, and Nitrocellulose (NC).

On the other hand, when the present invention is used to desulfurize coal, the solid material consists of coal particles and the unwanted compound will be sulfide mineral particles contained within the coal particles. In the biooxidation of refractory sulfide ores, the solid material will typically be a milled ore sulfide concentrate prepared from the ore, and the unwanted compound will be a metal sulfide particle in the ore or concentrate.

In some instances, it may be advantageous to prepare the concentrate by flotation or other means of concentrating a fraction of the solid material to be biotreated to a smaller weight fraction. If this concentrate contains the majority of unwanted metal sulfides or toxins, it can be processed more cost-effectively than, for example, the entire substance.

Those skilled in the art will appreciate that this method can be used to biotreat any solid material containing unwanted compounds that are susceptible to biodegradation or biooxidation by microorganisms or enzymes produced by microorganisms, as will be appreciated from above and below. The method according to the invention in that it can be used has a wide range of applications.

The purpose of using coarse substrates is to provide a support with a relatively large surface area in which the solid material to be biotreated may remain during the biotreatment process. Thus, many coated coarse substrates are stacked in heaps or placed in tanks to form non-surface surface reactors with a fairly large active surface area per m ³ of reactor space. The exact reactor surface area per m ³ of reactor space will depend on the specific size of the coarse substrate used, but should be at least 100 m ² per cm ³ of reactor, and typically will be at least 500 m ² per m ³ of reactor space. In addition, by using a coarse substrate having a particle size of about 0.3 cm or more and limiting the size of the solid particles to be biotreated to less than 250 μm, sufficient air and nutrients are accessible in all parts of the reactor during the bioprocessing process. Free up space. In this regard, the empty space in the reactor should be at least about 25%. Such void space will also dissipate heat properly within the bottom. In order to improve the access and heat dissipation of air and liquids, the empty space of the bioreactor can be set to about 35% or more. This will greatly speed up the progress of the biotreatment process.

The use of larger coarse substrates frees up space in the reactor, which increases air and nutrient access in addition to heat dissipation throughout the reactor, while larger substrates reduce the bioreactor loading capacity. Proper balance between ensuring sufficient void space and sufficient reactor capacity can be achieved using coarse substrates having a nominal particle size of about 0.6 cm to about 2.54 cm.

Various materials can be used as coarse substrates, including rock, gravel, volcanic rock, waste rock containing carbonate minerals, bricks, concrete blocks, slag and plastics. Volcanic rock is particularly preferred because of its rough and uneven surface, which improves the stability of the coating of solid materials applied to the substrate with a large surface area for substrates of a certain particle size. When acids react with carbonate minerals and slowly release carbon dioxide, coarse waste-rock containing carbonate minerals is free when the bioprocessing process is acidic, since the carbon dioxide can be used as a carbon source to carry out metabolic synthesis. Do. The production of carbon dioxide can thus promote microbial growth in the reactor.

Crude ore particles can be used as coarse substrates when biooxidizing refractory sulfide ores or sulfide concentrates to reduce the sulfide mineral content therein. Similarly, when the process is used to desulfurize ore, coarse coal particles can be used as coarse substrate. In both cases, the substrate may be advantageous for the biooxidation process carried out on its surface.

Although it has been defined that the particle size of the coarse substrate is greater than about 0.3 cm, it is also contemplated that some coarse substrate materials may actually be smaller than this. Those skilled in the art will appreciate that if a coarse substrate is produced by grinding a large material into the desired particle size range, the ground material will have a specific size distribution. In addition, even if screened to exclude materials less than about 0.3 cm, some materials smaller in particle size than the 0.3 cm target minimum will still be present in the coarse substrate due to inherent inefficiencies during the screening process and particle wear during processing. Thus, greater than about 0.3 cm means that almost all of the coarse substrate is larger than this size so that the empty space of the reactor remains at least about 25% during the formation and operation of the reactor. Preferably the amount of coarse substrate smaller than the limit of 0.3 cm is less than 5% by weight.

In general, the solid material to be biotreated will have to be much smaller than the coarse substrate it coats. These materials are usually polished to a small enough size so that the microorganisms used in the biotreatment are longer than the agitation tank method of the whole material and biooxidized or biodegraded in less time than the method by accessing all the materials to the bottom. Should be. Generally this time will be between 14 and 90 days depending on the unwanted compounds and their biodegradation or biooxidation rates.

The maximum solid material particle size was adjusted to about 250 μm so that the solid material formed a relatively uniform coating on the coarse substrate rather than forming aggregates among themselves during the coating process. Moreover, particles larger than 250 μm do not adhere well to the surface of the coarse substrate without the use of a binder.

The formation of a relatively uniform coating of fine particles on the coarse substrate during the coating process is desirable in that it maximizes the surface area of the solid material exposed to the active microorganisms added to the bioreactor and the stability of the coating. If aggregates of solid material are formed during the coating process, the solid material particles inside the aggregates will be blocked from the action of the microorganisms so that their biological throughput will be reduced or absent. Aggregates are also structurally incomplete, such as coated substrates, and are susceptible to breakage during lamination processes used during reactor formation or during biotreatment, which can lead to blockage generation within the reactor and to seal off portions of the reactor from biological treatment.

Typically, the smaller the particle size of the solid material to be biotreated, the faster the biotreatment process will be and the more solid material will be able to fill the coarse substrate. Smaller particle sizes will also tend to adhere better to the surface of the coarse substrate. However, if the particle size of the solid material to be treated is less than about 25 μm, excess dust problems may arise in handling and some coagulation may occur in the coating process.

Preferably the particle size of the solid material to be treated has a nominal particle size of about 75 μm to about 106 μm. Particles in this size range will adhere well to the coarse substrate, and the additional benefit that can be achieved with finer particle sizes at the biotreatment process rate is almost offset by the additional polishing cost in producing them.

Coated substrates can be prepared by adding coarse substrates and solid materials to the rotating drum in sufficient amounts. Preferably the coarse substrate is dry and the solid material is preferably left in the coarse substrate when the coarse substrate is applied to the slurry in the form of a high pulp density slurry. Alternatively, both the coarse substrate and the solid material are dry when applied to the rotating drum, and spraying water on the drum may facilitate the attachment of the solid material to the coarse substrate. When forming the coated substrate, it is desirable to maintain the moisture content of the solid material within 5-30% by weight to promote proper adhesion between the solid material and the coarse substrate.

Those skilled in the art have many other techniques that can be used to coat the coarse substrate. For example, a solid material to be biotreated may be sprayed onto the coarse substrate in the form of a high pulp density slurry while stacking a plurality of coarse substrates to form a reactor.

Once the solid material to be biotreated is applied to the slurry, the material can be adjusted to optimize the biotreatment process. For example, the pH can be adjusted to the optimum pH range of the microorganisms used to destroy unwanted compounds. If nutrients, supplements or inoculum are needed, these may also be added at this time. In some cases it may be advantageous to initiate a bioprocess in a tank prior to applying particles of solid material to the coarse substrate.

The stability of the coated coarse substrate should be sufficient to inhibit the formation of many blockages in the flow channel of the reactor during biotreatment of solid material particles on the surface of the coated substrate. Such blockages reduce the rate of biotreatment processes by reducing oxygen flow and microbial migration in the bioreactor. Of course, the larger the coarse substrate relative to the particle size of the solid material, the less likely such interference will be because the solid material is much smaller than the gap between the rough surfaces. The stability of the coated substrate will also have to be sufficient to ensure that no excess amount of solid material is washed away from the bioreactor during the biotreatment process.

In most cases, the surface tension of water fixes the particles of solid material to the surface of the coarse substrate, but it has been found that the particles of solid material are washed away from the bioreactor in excessive concentrations or the bioreactor is created by decomposition of the coating. If desired, binders can be used to improve the stability of the coating. However, the binder may prolong the time needed for the biotreatment process to reach the desired target point because the biotreatment may interfere with access to some solid material that is to be biotreated.

It is desirable that the thickness of the solid material coating on the plurality of coarse substrates is less than about 1 mm so that the microorganisms used in the biotreatment have adequate access to all solid materials to be treated. Thicker coatings increase the capacity of the bioreactor, but will limit the access of the microorganisms used for the underlying particles of the solid material, which will slow the progress of the biotreatment process. To fully utilize the capacity of the bioreactor while ensuring adequate microbial access, the thickness of the solid material coating is from about 0.5 mm to about 1 mm. When rock or brick substrates are used they will be modified to a solid material loading of about 10 to 30% by weight.

Comparative surface reactors are formed by stacking multiple coated substrates in heaps or in tanks. Conveyor lamination will minimize the density of the coated substrate in the reactor. However, other lamination means can also be used.

Preferably the reactor is inoculated with the microorganisms to be used in the biotreatment process during the formation of the control surface surface reactor by stacking a plurality of coated substrates or immediately after formation of the reactor. Alternatively, if the microorganisms to be used in the biotreatment process work optimally in a particular pH range, the pH of the reactor may be adjusted before inoculation, as is well known to those skilled in the art.

The microorganisms used in the present biotreatment process are the same microorganisms that have conventionally been used to degrade certain unwanted compounds in biodegradation and biooxidation processes. For example, a thio Bacillus Perot oxy thiooxidans (Thiobacillus ferrooxidans), reptoseupi rilrum Perot oxy thiooxidans (Leptospirillum ferrooxidans) and alcohol follower bus (Sulfolobus) and acidophilic, autotrophic bacteria in the biological oxidation of coal desulfurization or refractory sulfide minerals such as It can be used to biooxidize sulfide minerals. Other bacteria useful for this purpose are well known to those skilled in the art. Similarly, with regard to soil treatment, the microorganisms that should be used are the same as those currently used in composting, land farming, slurry biodegradation and heap sediment bioremediation. Those skilled in the art will be able to readily determine the microorganisms that can be applied to various unwanted compounds that can be removed from solid materials using the method according to the invention.

After inoculation of the appropriate microorganisms into the reactor, such conditions as pH, temperature, nutrient supply and moisture content in the reactor should be monitored and such conditions maintained throughout the biotreatment to facilitate the microorganisms to multiply as much as possible. As microorganisms multiply throughout the reactor, the reactor has a surface area that biodegrades or biooxidizes unwanted compounds to a greater extent in a shorter time than conventional static batch biotreatment methods such as bottom bioleaching, composting and land farming. Switch to a very wide bioreactor.

The reactor may also be provided with a porous air pipe capable of venting or introducing air as is well known in the art. The discharge or inlet of air through the reactor depends on the specific bioprocess occurring in the reactor, and such choices are well known to those skilled in the art.

The biotreatment process should be allowed to proceed until the unwanted compound in the solid material decomposes to the desired concentration. In the case of soil treatment laws, they will usually be regulated by government regulations that limit the acceptable levels of certain pollutants. In the coal desulfurization reaction, sulfur dioxide is produced as a by-product when the sulfur-containing coal is burned, so the residual amount of sulfur allowed in the coal also depends largely on environmental legislation. Therefore, the allowable amount of sulfur remaining in coal should be lower than the level that violates environmental regulations when coal is burned. To some extent, of course, it will depend on the equipment used in the coal ignition plant where biotreated coal will be used. Regarding the biooxidation of refractory sulfide ores or concentrates, the residual amount of sulfide minerals allowed in the ore will be regulated by the amount that must be biooxidized to economically recover the desired useful metals from the ore or concentrate.

After the unwanted compound has been reduced to the desired concentration, the bioreactor can be destroyed and the biotreated solid material can be separated from the coarse substrate. After separating the biotreated solid material, the coarse substrate can be reused. After more than one use in the biotreatment process, the membrane of microorganisms used in the biotreatment process will grow on the substrate. This microbial membrane is advantageous for application to any toxin or inhibitory material present in the solid material to be processed. Thus, it is best to remove the biotreated solid material in a manner that does not completely remove or kill the microbial film formed on the coarse substrate. Microbial membranes are the most effective way to inoculate the next coating of solid material applied to the coarse substrate. Finally, the application of microorganisms after several processes will speed up the rate at which microorganisms biodegrade or biooxidize unwanted compounds in the solid material to be treated.

The present invention will also be described in more detail in connection with many possible embodiments that can be used in the treatment of refractory sulfide ores.

A second embodiment of the invention is described with reference to FIGS. 1 and 2. 1 shows a process flow diagram for the liberation and recovery of precious metals from precious metal containing refractory sulfide ores. To illustrate the process shown in FIG. 1, sulfide mineral concentrates 22 used in embodiments of the present invention are made from gold containing refractory sulfide ores. Therefore, the precious metal recovered in this embodiment is gold. However, as will be appreciated by those skilled in the art, other precious metals such as platinum and silver may also be advantageous and recoverable from refractory sulfide ores using the process shown in FIG. If the refractory sulfide ore used to prepare the sulfide mineral concentrate 22 contains at least one precious metal, a mixture of precious metals can also be recovered using the process according to this embodiment.

According to the process flow diagram shown in FIG. 1, a plurality of substrates 20 and sulfide mineral concentrates 22 are added to the rotating drum 24. Preferably the sulfide mineral concentrate 22 is in slurry form upon addition of the rotary drum 24 and the plurality of substrates 20 are dry to improve adhesion between the substrate 20 and the concentrates 22. In some instances, a polymeric binder may be added to the rotating drum 24, although not necessarily. As the rotating drum 24 rotates, the substrate 20 added to the drum 24 is coated with a wet sulfide mineral concentrate 22 to form a coated substrate 39. The coated substrate 39 is then laminated to form a static heap 26.

Use of the slurry in the concentrate in the coating process eliminates the cost and necessity of drying the concentrate after it has been prepared. However, the concentrate 22 and the plurality of substrates 20 may also be added to the rotating drum 24 in a dry state, in which case the mixture is added to the drum 26 and preferably contains iron ions. Spray the aqueous solution of water or acid to allow the concentrate to stick to the substrate. The advantage of using an acid aqueous solution containing iron ions to bind the concentrate to the surface of the substrate is that it starts chemically oxidizing the sulfide mineral concentrate. It will also lower the pH of the coated substrate 39 in the sample for biooxidation because it is acidic. The disadvantage of using such an acid solution is that it increases the cost of the device because the device used to form the coated substrate 39 must be designed to be acid resistant.

Sulfide mineral concentrate 22 consists of a number of fine metal sulfide particles 40 containing finely dispersed gold and possibly other precious metals. Sulfide mineral concentrate 22 also typically comprises fine particles of sand or other gangue material 42 from refractory sulfide ore to obtain concentrate 22. As a result, each coated substrate 39 will be coated with metal sulfide particles 40 and fine particles 42 as shown in FIG. 2.

The stability of the coated substrate 39 should be sufficient to prevent the formation of a number of blockages in the flow channels in the bottom 26 while the metal sulfide particles 40 on the surface of the coated substrate are biooxidized. Such blockages reduce the rate of biooxidation by reducing oxygen flow and bacterial transport in the hips.

Since the metal sulfide particles 40 are hydrophobic they will tend to be fixed to the dry substrate 20 without the use of a binder such as a polymer flocculating aid. However, it is assumed that the metal sulfide particles 40 are of a suitable size. Thus, if the concentrate 22 contains metal sulfide particles 40, the concentrate 22 is sufficiently secured to the coated substrate 39 without the use of a binder and in connection with the embodiment shown in FIG. Coated substrate 39, described in, is made operable during lamination with heap 26 or placed in a tank. In addition, the coated substrate 39 must retain their stability throughout the biooxidation process. Thus, when forming the coated substrate 39 without the use of a binder, it is important to use sulfide mineral concentrates having the appropriate concentration and suitable particle size of the metal sulfide particles.

Using such a binder will increase the operating cost of the process as long as it improves the stability of the coated substrate 39 using a polymeric binder.

There are at least two factors that act on using the sulfide mineral concentrate 22 with a very high concentration of the metal sulfide particles 40. The first factor is that the cost of producing the concentrate 22 is typically proportional to the concentration of the metal sulfide particles. Thus, as the concentration of metal sulfide particles 40 increases in concentration 22, the production cost of concentrate 22 will likewise increase. Additional costs in the manufacture of the highest concentrates 22 will be offset by the loading of metal sulfides or by an improvement in the stability of the coated substrate 39. The second factor is that as the grade of concentrate increases, the amount of metal sulfide particles 40 remaining in the residue fraction of the refractory sulfide ore also increases. Since these metal sulfide particles contain occluded precious metals, all metal sulfide particles 40 remaining in the tailings of the ore will reduce the total recovery during the process.

In view of the above factors, the sulfide mineral concentrate 22 should contain at least 20% by weight of metal sulfide to ensure ophthalmic and proper handling properties and preservation during biooxidation. However, preferably the concentrate should comprise at least about 40%, more preferably at least about 70%, by weight metal sulfide. Typically concentrate 22 will comprise about 40 to 80 weight percent metal sulfide.

Typically, the smaller the particle size of the sulfide mineral concentrate 20, the faster the biooxidation process will proceed. In addition, smaller particle sizes tend to improve concentrate grades. This is because, when the particle size of the ore is reduced, it is typically easier to separate the metal sulfide particles 40 from the large volume of gangue material. Thus, the sulfide mineral concentrate 22 preferably has a particle size of less than 250 μm. Particles larger than 250 μm will not adhere well to the substrate without the use of a binder. In addition, it is difficult to obtain a good separation of the metal sulfide particles 40 from a large volume of gangue material during concentration unless the refractory sulfide ore from which the concentrate 22 is made is polished to 250 μm, which is at least 100% acceptable. Since particles larger than 250 μm do not float well, this is especially true when the concentrate 22 is prepared using the flotation method. On the other hand, when the particle size of the concentrate 22 is less than about 38 μm to 25 μm, the concentrate particles tend to agglomerate together during the coating process rather than to form a relatively uniform coating on the coated substrate 39. Will indicate. Such aggregates of concentrate can block air flow and bacterial migration during biooxidation, thereby reducing the rate of biooxidation at the bottom.

Preferably, the particle size of the concentrate 22 is 106 to 75 μm, which is about 100% acceptable. Particles in this size range adhere well to the substrate 20, and the increased improvements that can be achieved in concentrate grades with biooxidation rates and finer particle sizes are largely offset by the additional polishing cost of producing them.

The sulfide mineral concentrate 22 does not need to be described in detail herein because it can be made from all precious metal containing refractory sulfide ores to be mined using techniques well known in the art. However, the preparation of concentrate 22 will typically include one or more gravity separation methods or one or more sulphide flotation methods after grinding and milling refractory sulfide ores to the appropriate particle size.

Some potential refractory sulfide ores may already be of sufficient grade that no additional concentration is needed. Such ores include beneficiation debris or waste heaps in existing mines. When treating this type of ore, the sulphide mineral concentrates simply need to be moved to the location of the biooxidation plant and perhaps only some additional grinding is necessary to achieve the desired particle size.

With regard to gold concentration, the method according to this embodiment can be carried out economically even if the concentrate 22 contains as little as 5 g Au / ton (or the equivalent economic value of other precious metals) of the concentrate. The number of methods will vary greatly depending on the market price of gold and the cost of producing the concentrate 22. However, those skilled in the art will recognize that traditional autoclave or stirred tank bioreactors cannot be approached economically with such low concentrations of sulphide mineral concentrates.

Many different materials can be used as the substrate 20. Preferred substrates include waste rock containing coarse refractory sulfide mineral particles, volcanic rock, gravel and mineral carbonate components. Substrate 20 may also be an artifact, such as plastic balls, recycled styrofoam, worn tires, and the like. The purpose of the substrate 20 is to provide a support having a relatively large surface area in which the concentrate 22 resides during the biooxidation process. The surface area of each substrate 20 actually functions as a small surface bioreactor in biooxidation. Thus, a large number of coated substrates 39 are laminated into the heap for biooxidation, making a comparative surface bioreactor with a very high total surface area.

Make a water reactor.

The total surface area of the bioreactor or the bottom 26 is reduced by using a substrate having a rough uneven surface morphology and / or by reducing the particle size of the substrate 20 by increasing the number of covered substrates 39 deposited on the bottom 26. Can be increased. The advantage of increasing the total surface area of the substrate 20 in the hips 26 proportionally increases the amount of concentrate 22 that can be loaded onto the substrate 20, thus biooxidizing at a particular heap 26. To increase the amount of concentrate 22 that may be present.

The preferred particle size range of the substrate 20 is from about +0.62 cm to about -2.5 cm and particles smaller than about 0.3 cm are removed by screening or other suitable method. However, substrates with particle sizes up to about +600 μm ( 20) can be used. Smaller substrate particle sizes increase loading, while larger particle sizes increase air flow, fluid flow, and heat dissipation. The nominal +0.62 to -2.5 cm size range provides a reasonable compromise between concentrate loading and adequate air flow, fluid flow and heat dissipation.

Substrate 20 is preferably loaded with as much concentrate 22 as possible during the coating process to maximize process throughput. The amount of concentrate 22 that can be loaded onto the substrate 20 will depend on the particle size and surface morphology of the substrate 20. Thus, the coarse substrate 20 and the sulfide mineral concentrate 22 in order to minimize the formation of aggregates of sulfide mineral concentrate particles, while maximizing the amount of sulfide mineral concentrate 22 loaded on each substrate 39. Should be added to the rotating drum 24 in a sufficient amount. Agglomerates or aggregates of sulfide mineral concentrate 22 particles may be formed if the particle size of the concentrate is too fine or excess concentrate is added to the drum 24 as described above. In order to prevent agglomeration of the concentrate particles and at the same time to ensure proper loading on the substrate 20, preferably about 10 to 30% by weight concentrate is added to the rotary drum 24, resulting in about 10 to 30% by weight. Concentrate 22 will be loaded onto the coated substrate 39.

When preparing the coated substrate 39, it is desirable to maintain the moisture content of the concentrate 22 within 5 to 30% by weight. If the moisture content of the concentrate is less than 5% by weight, the concentrate will not adhere properly to the substrate, and if the moisture content exceeds 40% by weight the concentrate slurry will be too thin to form a sufficiently thick coating on the substrate. This will limit the amount of concentrate that will be attached to substrate 20.

Other bottom fabrication methods can be used, but conveyor lamination is preferred. Conveyor lamination minimizes densification of the coated substrate in the bottom. Other means of lamination, such as end dumping or top dumping with a dozer, can result in areas with reduced fluid flow in the bottom due to increased density and resolution of the coated substrate.

If desired, a porous tube 27 connected to an air source (not shown) may be installed in the hip 26 to increase the gas flow in the hip 26. Increasing airflow in the bottom 26 will improve the rate at which heat is dissipated from the bottom and increase the rate of biooxidation. Moreover, because of the large air and fluid flow channels between the coated substrates 39, the air source connected to the porous tube 27 will be a low cost ventilator rather than an expensive compressor.

The coated substrate 39 heaps bacteria that can biooxidize the metal sulfide particles 40 when deposited on the heap 26 or immediately after formation of the heap 26 or after lowering the pH of the heap below 2.5. It is preferable to inoculate at (26). Thiobacillus ferrooxidans , Thiobacillus thiooxidans , Thiobacillus organoparus , Thiobacillus acidophilus , Leptospirylrum ferrotodans ferrooxidans , Sulfobacillus thermosulfidooxidans , Sulfolobus acidocaldarius , Sulfolobus BC, Sulfolobussolfataricus and Assydianus brierleyi Such bacteria can be used in the present invention.

All of these bacteria can be obtained from the American type culture collection or similar culture collections. One or more of the above bacteria and the particular bacteria selected for use in the methods of the present invention will depend on factors such as the type of ore treated during biooxidation and the expected temperature at the bottom 26. However, these selection criteria are well known to those skilled in the art and are not described in detail herein. The most common and preferred bacterium for biooxidation is thiobacilli ferrooxydans.

During the biooxidation of the metal sulfide particles 40 on the surface of the coated substrate 39, additional inoculum and microbial nutrient solution may be fed through the water system 28. The addition of these bioleaching preservation solutions will be made in accordance with the specific working indicators used to monitor the progress of the biooxidation process.

The rate of biooxidation throughout the biooxidation process is preferably monitored based on selected work indicators such as the rate of dissolution of arsenic, iron or sulfur or the rate of oxidation of sulfides that can be calculated from them. Other biooxidation work indicators that may be used include pH, titratable acidity and solution Eh measurements.

Preferably, the bioleaching drainage solution that bleeds through the hips is collected in the drain pipe 29 and recycled to the upper layer of the hips 26. This minimizes the amount of new water needed for the biooxidation process. In addition, because the bioleaching discharge solution will be acidic and contain high concentrations of iron ions, it is advantageous for the biooxidation process to be reused as an upper layer of the heap 26. However, the release solution initially generated in the biooxidation process will also include significant concentrations of nonmetals and heavy metals, including components that induce microbial inhibition. The biooxidation process is slowed down by the generation of inhibitors in the bioleaching drainage solution. In fact, continuing to recycle the drainage solution without treatment may produce enough inhibitory material to stop the biooxidation process.

In order to minimize the production of inhibitory substances and their effects on the biooxidation process, the drainage solution can be treated in the acid circuit 30 prior to recycling to remove the inhibitory substance when the concentration of the inhibitory substance becomes excessive. . One method of adjusting the bioleaching discharge solution prior to recycling involves raising the pH above 5, removing all the resulting precipitate and then lowering the pH to the appropriate pH using an untreated discharge solution or other acid solution. Such a control method is disclosed in US Patent Application No. 08 / 547,894 to Koh et al., Filed October 25, 1995, which is incorporated herein by reference.

The bioleaching discharge solution will be very acidic in the present invention. This is due to the fact that, rather than all ores, concentrates with relatively high concentrations of metal sulfide minerals are biooxidized. As a result, the biooxidation process according to the present invention is likely to produce a large amount of excess acid. That is, this method will actually produce a greater amount of acid than can be recycled to the top of the bottom 26. This excess acid should be discarded or used for other purposes. Excess acid can be used in copper oxide ore leaching processes because sulfuric acid is an effective leaching agent for copper oxide ores. However, the sulfuric acid solution produced as a by-product of the process will also typically contain high concentrations of iron ions. It also functions as an effective leach agent for some copper sulfide ores such as whiskers. Iron ions in the acid solution chemically oxidize the copper sulfide minerals to separate them. Therefore, excess acid from this method can be advantageously used in the copper leaching operation, thereby reducing the acid cost in the copper leaching operation and at the same time avoiding the neutralization cost of disposal.

After the biooxidation reaction reaches an economically defined target point, i.e., after the metal sulfide particles 40 on the surface of the coarse substrate 20 are biooxidized to the desired degree, the heap is broken to coarse the biooxidized concentrate 22. Separate from substrate 20. However, prior to breaking the heap, the heap is usually drained and then flushed repeatedly with water to wash. The number of washes used is usually determined by the pH of the wash emissions and suitable labeling elements such as iron.

Separation can be accomplished by placing the coated substrate 39 on a screen and then spraying the coated substrate with water. Alternatively, the coated substrate can be trammed with water using trommel.

After separation, gold is extracted from the biooxidized concentrate 22. This can be done using many techniques that are well known in the art. Typically, however, the biooxidized concentrate will be leached with a leaching agent, such as cyanide, in the process of carbon-in-pulp in carbon or carbon-in-leach in leach. In this process, leaching agents, as is well known in the art, dissolve free gold or other precious metals and they are adsorbed onto activated carbon.

If cyanide is used as a leaching agent, it will be necessary to neutralize the concentrate before leaching. To rule out this need for neutralization, thiourea can be used as a leaching agent to extract gold from the biooxidized concentrate. Thiourea extraction processes can be improved by adjusting the Eh of the leaching solution using sodium metabisulfite as disclosed in US Pat. No. 4,561,947, which is incorporated herein by reference. If thiourea is used as a leaching agent, preferably dissolved noble metals are adsorbed from the leaching solution using synthetic resins rather than activated carbon.

After freed gold or other precious metals are extracted from the biooxidized concentrate, the biooxidized concentrate is transferred to wastewater or beneficiation residues (36), and gold is recovered from carbon or synthetic resins using techniques well known in the art. do.

The coarse substrate 20 separated from the biooxidized concentrate can be recycled to a rotating drum for fresh coating with the sulfide mineral concentrate 22. Substrate 20 can be reused as long as they retain mechanical stability. If coarse refractory sulfide ore particles are used in the substrate 20, they are treated at various points to recover the free gold, preferably after 1 to 3 turns.

As shown in FIG. 2, the coarse refractory sulfide ore substrate 20 will comprise metal sulfide particles 40 containing occluded gold and other precious metals. After 1 to 3 cycles through the process, many metal sulfide particles 40 in the ore substrate 20 will be partially biooxidized. Rather than continuing to recycle the ore substrates in this situation to release free metals that are freed, the ore substrates can be treated to recover gold. This may preferably be done by polishing the ore substrate in the polishing circuit 32 to a particle size suitable to allow metal sulfide particles to separate from the mass of gangue material. A concentrate 22 of metal sulfide particles 40 obtained from the polished ore substrate is then produced in a sulfide concentrator 34. Preferably the sulfide concentrator 34 is a flotation beneficiation cell, and the biooxidized hematite substrate is polished to a size suitable for the sulfide flotation beneficiation and coating on the substrate 20. Then, the concentrate 22 obtained from the polished ore substrate is combined with the feed of sulfide mineral concentrate 22 coated on the second plurality of coarse substrates 20, and the new heap 26 for further biooxidation. Add to

The flotation debris from the sulfide concentrator 34 must be treated with the biooxidized concentrate 22 from the bottom 26 in the gold extraction process. Flotation beneficiation will include a number of fully and partially oxidized metal sulfide particles that are not suspended beneficiation. These oxidized particles will contain significant gold, and since much of these gold would have already been liberated, they can be easily leached from the flotation residue using cyanide or thiourea. After leaching, the suspended beneficiation debris is treated with biooxidized concentrates subjected to gold extraction from waste or beneficiary debris deposits 36.

Alternatively, the refractory sulfide ore substrate 20 which has undergone the biooxidation process can be treated simply by leaching it after polishing. However, because the metal sulfide particles 40 in the ore substrate are not oxidized sufficiently to liberate the gold trapped therein, the total recovery of this method will be low.

In the selection of the substrate 20 material there are several advantages of using refractory sulfide ore particles.

First, the mined refractory sulfide ore typically has to undergo several grinding and polishing steps until it reaches a particle size suitable for producing the concentrate 22. As a result, the coarse refractory sulfide ore substrate can be removed at a suitable stage of the grinding process, so the coarse refractory sulfide ore particles are a low cost raw material of the substrate 20.

Second, as shown in FIG. 2 and described above, when coarse refractory sulfide ore is used as the substrate, it will include metal sulfide particles 40. These metal sulfide particles will be partially biooxidized during the biooxidation process, and when the ore particles are recycled through the process several times, the metal sulfide particles 40 are sufficiently biooxidized to allow recovery of these precious metals.

A third advantage, somewhat related to the second, is that fractions of iron sulfide or other metal sulfide particles 40 in refractory sulfide ores are fine enough that they are not well suspended in the concentration process. By using coarse particles of ore as substrate 20, these very fine metal sulfide particles will be chemically oxidized to the end by iron ions in the bioleach. When the coarse ore particles are finally polished and suspended to produce a concentrate of the metal sulfide particles, the oxidized fine metal sulfide particles will eventually become suspended beneficiation debris. Free gold will be recovered from these very fine sulfide particles because of the leaching of flotation debris with cyanide or other leaching agents. On the other hand, if the coarse ore particles are not used as the substrate 20 before polishing and flotation, the very fine metal sulfide particles will still remain as flotation residue when preparing the concentrate 22. However, since these very fine sulfide particles are not partially biooxidized at this point, their occluded gold cannot be recovered by leaching.

A fourth advantage of using refractory sulfide ore as substrate 20 is that metal sulfide particles in the biooxidized support material are more easily suspended after biooxidation. This is because the surface of the metal sulfide particles is changed in the biooxidation process. Thus, after several uses of the ore support material, it can be polished suspended to produce sulfide mineral concentrates and improved floatability.

If the coarse ore particles also contain a carbonate mineral component, there is a fifth advantage of using coarse refractory sulfide ore particles as the coarse substrate 20. Carbonate minerals tend to be very acid consuming. As a result, ores containing these minerals typically required excess acid prior to biooxidation. Acid treatment of these ores is necessary to remove or reduce the carbonate mineral component prior to biooxidation to the extent that the biooxidation reaction can proceed. In addition, coarse refractory sulfide ore particles generally tend to biooxidize very slowly (when large amounts of carbonate minerals are included in the ore, often taking more than nine months), and without pretreatment, the ore particles may never be biooxidized. have. In the process according to the invention, however, coarse refractory sulfide ore particles containing carbonate minerals can be advantageously used for the substrate 20. During the biooxidation process, the acid produced from the biooxidation of the concentrate 22 on the surface of the crude ore substrate will slowly neutralize the carbonate mineral in the substrate. The by-product of the neutralization process is carbon dioxide, and autotrophic bacteria used in the present invention can perform metabolic synthesis using carbon dioxide as a carbon source. Thus, carbon dioxide production will promote bacterial growth at the bottom 26, which will increase the rate of biooxidation of the concentrate 22. Thus, by using the coarse ore containing carbonate mineral as support material 20, the coarse mineral will gradually be neutralized in the next biooxidation process, and bacterial growth in the hip 26 will be promoted. The simultaneous benefit would be the biooxidation of very fine non-suspended sulfide particles in the coarse mineral, as described above.

As will be appreciated by those skilled in the art, the coarse refractory sulfide ore particles used in the substrate 20 should not be derived from the same ore used to prepare the concentrate 22. Indeed, in some cases, it may be advantageous to use concentrate 22 obtained from the ore substrate 20 obtained from one ore and another ore. For example, one ore may be easily concentrated or may already have the desired properties of the concentrate, while another ore may have a high concentration of carbonate minerals. In this situation, it would be advantageous to prepare concentrate 22 from the first ore and to prepare the substrate 20 from the second ore. In this way, the ore obtained from the second ore can be neutralized against biooxidation while simultaneously improving the biooxidation results of the concentrate obtained from the first ore. Similarly, where the ore contains a high concentration of metal sulfides that are difficult to float, improved floatability can be achieved by first using ore as the light ore substrate 20 in the method according to the invention.

Other preferred materials as substrate 20 include coarse rocks containing volcanic rock, gravel and carbonate minerals. Substrates of this type are commonly used when the mined refractory sulfide ore is a waste heap or beneficiation debris deposit, and as a result, the ore is already ground and polished.

The advantage of using volcanic rock is that the total surface area of the substrate 20 is large for a given particle size because it has a very rough, non-uniform surface morphology. Thus, for a given particle size, volcanic rock can be loaded with more concentrate than other substrates with smoother surfaces.

Gravel is typically a low cost substrate material while having a very smooth surface. Coarse rocks containing carbonate minerals are advantageous because, as described above, when the acid from the biooxidation process neutralizes the carbonate minerals, they slowly generate carbon dioxide. Substrates of this type can preferably be reused in the process as long as carbon dioxide continues to be generated during the biooxidation process.

A third aspect of the invention will now be described with reference to FIG. 3. The method according to this embodiment is essentially a variation of the embodiment described in connection with FIG. 1. Thus, of course, the similar terms are referred to by the same reference numerals and the descriptions and considerations expressed with respect to each of these terms in relation to FIG. 1 apply equally to this embodiment.

In a second embodiment, the method according to this embodiment can be used to release and recover precious metals from precious metal containing refractory sulfide ores. However, for illustrative purposes, it is assumed that sulfide mineral concentrate 22 is made from gold containing refractory sulfide ores.

A plurality of substrates 20 according to this embodiment are coated in a rotating drum 24 with sulfide mineral concentrates 22 to produce a plurality of coated substrates 39. Subsequently, a plurality of coated substrates 39 are laminated to the hips 26 and used as a large control surface bioreactor.

The various considerations described above relating to substrate 20, sulfide mineral concentrate 22, production of coated substrate 39 and production of hip 26 are all equally applicable here.

After the hips 26 are formed, the hips are inoculated with biooxidized bacteria to initiate the biooxidation process. As the biooxidation process proceeds, additional sulfide mineral concentrates 22 may be added to the top of the hips 26. The advantage of adding additional sulfide mineral concentrate 22 to the top of the heap 26 throughout the biooxidation process is that it can increase the amount of concentrate that is processed in the heap until it breaks and reforms. In addition, if coarse refractory sulfide ore is used as the substrate 20, the concentrate 22 will be easier to biooxidize more quickly than the metal sulfide particles 40 in the crude ore. Thus, by adding additional concentrate 22 to the top of the heap 26, the biooxidation degree of the ore substrate will be increased before breaking the heap. In addition, the acid and iron ions produced during the biooxidation by adding sulfide mineral concentrate 22 to the top of the heap 26 are due to the lack of toxins or oxygen in which bacterial growth is not initially washed from the ore in the biooxidation process. It will move to the lower part of the hip which can be suppressed. As a result, the biooxidation of sulfide mineral concentrates and ore substrates will proceed even though bacterial growth at this site is not favorable.

Adding the sulfide mineral concentrate 22 to the top of the heap 26 after biooxidation for some time is another advantage in that it increases the rate of biooxidation at the heap. In the second half of the biooxidation of the coated substrate 39, most of the exposed and reactive sulfide will already be oxidized so that the rate of biooxidation will slowly decrease. This slow drop in biooxidation rate can lead to a sharp drop in the amount of iron in the bottom 26 and an increase in pH. The addition of a new reactive sulfide mineral concentrate 22 on top of the heap 26 can resume the active biooxidation process due to the high content of divalent iron due to the biooxidation of the added concentrate, which in turn results in a substrate Indirect chemical leaching of the sulfide mineral concentrate 22 coated on 20 and the metal sulfide particles embedded in the ore substrate 20 will be increased.

Fresh concentrate 22 may be added to the top of the heap 26 until the flow channels in the heap begin to clog with the concentrate and the biooxidized residue therefrom.

In a second embodiment different from the embodiment of FIG. 1, a second variant relates to a method for recovering precious metals from the bottom after biooxidation. In this embodiment, instead of separating the biooxidized concentrate from the heap for gold extraction after destroying the heap, directly leaching the heap with a noble metal leaching agent from the biooxidized concentrate (substrate if a light ore substrate was used). Extract gold. Leaching agents that work at low pH, such as thiourea, are preferred so that there is no need to neutralize the hips prior to leaching. Furthermore, the gold released by using leaching agents compatible with thiourea or other acids can be intermittently extracted from the bottom. For example, the heap 26 biooxidizes for a period of time and then releases the gold extracted with a suitable leach agent, and then the biooxidation process is resumed. Fresh concentrate 22 is added to the top of the bottom 26, preferably in the form of a slurry, with the resumption of the biooxidation process.

After reaching the desired degree of biooxidation, the bioleaching solution is first drained from the bottom to the acid circuit 30 to extract gold from the bottom 26. After discharging the hips, leachants compatible with acids, such as thiourea, are pumped from the leachant source 38 into the watering system 28 and dispersed onto the heaps 26. When the leaching agent seeps out of the bottom, it dissolves the gold liberated from the sulfide mineral concentrate 22 and the ore substrate. The loaded leachant is then recovered in a drain pipe 29 where the leachant is converted from the acid circuit to the gold removal process 44, where the gold removal process preferably comprises adsorbing the dissolved gold with activated carbon or synthetic resin. do. The waste leaching agent is then recycled to the leaching agent source 38 and the gold is recovered from the loaded activated carbon or synthetic resin. The removal of gold adsorbed from activated carbon and synthetic resins is well known in the art and need not be described herein.

The method according to the fourth embodiment of the present invention is described in FIG.

4 shows a method for liberating and recovering gold from sulfide ores. Since the method according to this embodiment has obvious similarities to the embodiment described in connection with FIG. 1, similar items are referred to by the same reference numerals. In addition, descriptions and considerations expressed in connection with the items related to FIG. 1 are equally applicable to the present embodiment.

According to this embodiment, sulfide mineral concentrate 22 is first produced from sulfide ore. Concentrate 22 consists of a plurality of fine metal sulfide particles 40 and fine particles of sand or other gangue material 42.

Many different sulfide ores can be used to produce sulfide mineral concentrates 22. Of the sulfide ores that can be treated in the process, the main ones are sulfide ores including sulfide minerals of nonmetals such as copper, zinc, nickel, iron, molybdenum, cobalt or uranium. Useful metals of interest in these ores are in the metal portion of the sulfide mineral particles in the ore. Thus, the free and recovered useful metals will depend on the particular sulfide mineral present in the concentrate 22 produced from the ore. For example, if the sulfide ore used in the manufacture of concentrate 22 contains zirconia, semi-orbit and / or chalcopyrite, the recovered useful metal will be copper. On the other hand, if the concentrate 22 is a concentrate of flash lead, the useful metals recovered will be zinc.

After the concentrate 22 is prepared, the sulfide mineral concentrate 22 is coated on a plurality of substrates 20 to form a coated substrate 39. This can be done by adding a slurry of a plurality of dry substrates 20 and concentrates 22 to the rotating drum 24 or alternatively, a plurality of dry substrates 20 and concentrates 22 as described in connection with FIG. Is performed by adding to a rotating drum and watering the mixture with an aqueous solution. A plurality of coated substrates 39 produced on the rotating drum 24 are stacked to form the hips 26, which form a large control surface surface bioreactor.

The various considerations described above regarding the production of the substrate 20, the sulfide mineral concentrate 22, the coated substrate 39, and the bottom 26 are all equally applicable here.

After the hips 26 are formed, the hips are inoculated with biooxidized bacteria to initiate the biooxidation process. When the metal sulfide particles 40 are biooxidized in the concentrate 22, the metal portion of the sulfide particles is dissolved in the bioleaching solution and seeps through the hips. The bioleaching solution seeps out through the bottom and is then recovered in the drain 29. The bioleaching solutions are then recovered by treating them to remove one or more desired nonmetals from the bioleaching solution using techniques well known in the art.

After the desired useful metals have been recovered from the bioleaching solution, the solution can be treated in an acid circuit 30 to remove all excess toxins as described in connection with FIG. 1 and then recycled to the top of the bottom 26.

Once the biooxidation reaction reaches an economically defined target point, that is, the metal sulfide particles 40 on the surface of the coarse substrate 20 are biooxidized to the desired level, then the hips are destroyed and the biooxidized concentrate is coarse substrate. Separate from (20). The biooxidized concentrate is then disposed of as waste or beneficiary debris deposit 36. However, when the present embodiment has been described in terms of freeing and recovering nonmetals in the metal portion of the metal sulfide particles 40 in the sulfide mineral concentrate 22, the sulfide particles 40 may also include occluded precious metals. Of course you can. Thus, after biooxidation of concentrate 22, all of the precious metals liberated in concentrate 22 may be extracted and recovered as described with respect to FIG. 1 prior to treating the biooxidized concentrate.

The coarse substrate 20 separated from the biooxidized concentrate can be recycled to a rotating drum for fresh coating with the sulfide mineral concentrate 22. Alternatively, when coarse sulfide ore particles are used as the substrate 20, they are preferably one or more times through the process of forming a sulfide mineral concentrate of all metal sulfide particles 40 remaining unoxidized in the crude ore substrate. Processed after the cycle. Sulfide mineral concentrate 22 is produced from biooxidized ore substrates as described in connection with the second embodiment.

The method according to the fifth embodiment of the present invention is shown in FIG. The method shown in FIG. 5 is for releasing and recovering noble metals from noble metal containing refractory sulfide ores using a comparative bioreactor. This method involves producing a concentrate 22 of metal sulfide particles 40 from refractory sulfide ores to be treated. The concentrate 22 is then coated onto a plurality of coarse substrates 20 using a rotating drum 24 as described in connection with the second embodiment to form a coated substrate 39. After formation, the coated substrate 39 is placed in a tank 45 for biooxidation. Substrate 39 is biooxidized in tank 45 such that a large non-surface surface bioreactor forms a very large surface area. Thus, the tank 45 replaces the hips 26 in the method according to the second embodiment. Thus, the various considerations described above in the second embodiment with regard to the production of the substrate 20, the sulfide mineral concentrate 22, the coated substrate 39 and the production of the hips 26 may be achieved in this embodiment by using a tank ( The same applies to the biooxidation of the substrate 39 coated in 45).

Upon biooxidation of the concentrate 22 on the coated substrate 39, the bioleaching preservation solution is added to the tank from the top using any of a number of known techniques. The bioleaching solution that bleeds through the tank is drained from the tank and treated in acid circuit 30 before being reused in the process as described in connection with FIG. 1.

Air can be introduced into the tank during the biooxidation process to increase the amount of oxygen in the bioreactor and improve heat dissipation. Air is preferably introduced into the tank 45 through a series of perforations 46 connected to a ventilator (not shown).

If desired, additional concentrate 22 may be added to the top of the coated substrate 39 in tank 45 throughout the biooxidation process. As noted above in connection with the third embodiment, the addition of additional concentrates to the bioreactor during the biooxidation process can maintain the biooxidation rate in the bioreactor at high levels throughout the biooxidation process.

The advantage of using a tank 45 above the bottom 26 for the bioreactor is to facilitate separation of the biooxidized concentrate 22 from the substrate 20. After bioconcentration of concentrate 22 to the desired target point, separation of substrate and biooxidized concentrate is performed by filling the tank with water and then draining the tank rapidly. Biooxidized concentrate will be transported with the drained water. This process can be repeated several times to improve the separation result. Tank 45 is also preferably equipped at the bottom of the tank with a screen having a network structure smaller than the size of the substrate but larger than the concentrate particle size to assist in the separation process.

After separation, the biooxidized concentrate is leached with a noble metal leaching agent to extract free gold or other precious metals. The dissolved gold is then recovered from the leaching agent by contacting the solution with activated carbon or synthetic resin. The leaching is preferably carried out in the presence of activated carbon or synthetic resin so that the dissolved gold is immediately removed from the solution in which they are dissolved. Gold adsorbed on activated carbon or synthetic resin can be recovered using techniques well known in the art.

Once the noble metal is extracted from the biooxidized concentrate, the concentrate can be disposed of as waste or beneficiary debris deposit 36.

In a second embodiment, the coarse substrate 20 separated from the biooxidized concentrate may be recycled to a rotating drum for fresh coating of the sulfide mineral concentrate 22. The substrate 20 can be reused as long as it retains their mechanical stability. If coarse refractory sulfide ore particles are used as the substrate 20, they are preferably recovered at some point, preferably after 1 to 3 cycles of processed free gold. This is done in the same way as described in connection with the second embodiment.

Another aspect of the invention is now described. In this aspect of the present invention, a method for recovering noble metals from concentrates of noble metal containing refractory sulfide minerals is described. The process comprises (a) dispensing a concentrate of fine refractory sulfide minerals to the top of the coarse support material, (b) biooxidizing a concentrate of refractory sulfide minerals, and (c) leaching agent from the biooxidized refractory sulfide minerals. Leaching the noble metals using, and (d) recovering the noble metals from the leach agent.

Concentrates of precious metal containing refractory sulfide minerals will typically be prepared from precious metal containing refractory sulfide ores. Concentrates can be prepared from such ores using known gravity separation or flotation processes. While gravity separation is cheap, flotation is the preferred separation method due to the selectivity of the process. The most commonly used collector for the concentration of sulfide minerals in the flotation process is xanthate. The xanthate flotation process is well known to those skilled in the art and therefore does not need to be described in detail herein.

Preferably, the particle size of the concentrate is from 80 to 90% of the concentrate less than 100 to 45 μm. More preferably, 80-90% of the concentrate is less than 150 μm and 100 μm.

However, the optimal size may vary for different types of ores. Typically, the operator should seek to obtain particle sizes that allow for optimal separation in the concentrate and provide optimum biooxidation rates for increased cost of additional micropolishing.

The smaller the particle size of sulfide minerals in the concentrate, the faster the concentrate will oxidize during the bioleaching process. However, faster biooxidation rates do not always offset the additional energy costs associated with fine grinding ore or flotation concentrates.

In the process according to this aspect of the invention, the cost of allowing the concentrate on the heap to biooxidize is minimal. Thus a slightly longer biooxidation period can be justified in that it avoids having to incur costs associated with further polishing. In this regard, the method is advantageous over the milling process. In milling processes, the economics of the process must be maintained by grinding the sulfide mineral concentrates very finely to ensure a high biooxidation rate so that the bioreactor can process as many concentrates as possible in the shortest possible time.

The sulfide mineral concentrate is produced and then distributed over the top of the bottom of the support material. Preferably, the concentrate is dispensed on top of the heap in slurry form so that it can be piped directly to the heap without having to first dry. The pulp density of the concentrate should be adjusted so that the concentrate flows well while the support material is not easily washed off from the heap. Because sulfide mineral particles are hydrophobic, they will adhere to the support material rather than pass through the hips if an appropriate support material is selected. Clogging of the flow channel will not be a problem if a suitable size of support material is selected.

The purpose of the support material is to capture and retain sulfide minerals as the support material slowly moves downward through the hips to function as a bioreactor with a large surface area. For this reason, support materials having a high porosity or rough surface are preferred because they tend to capture and retain concentrates. The greater the amount of concentrate the support rock can support without clogging the flow channel, the better. Support materials that can be used to practice this aspect of the invention include waste rock containing volcanic rock, gravel or small amounts of mineral carbonate as a CO ₂ source for biooxidizing bacteria. Other suitable coarse substrates are bricks, concrete blocks and slags. Volcanic rock is a particularly preferred support material because of its roughness and high porosity.

Support materials containing small amounts of mineral carbonates are advantageous not only in that they produce CO ₂ , but also because they help buffer the acid solution resulting from the biooxidation process. This makes it easier to adjust the pH of the bioreactor during the biooxidation process.

There are several conflicting interests to consider with regard to the selection of appropriately sized support materials. The smaller the diameter of the support material, the larger the surface area, thus increasing the effective area of the bioreactor made with the bottom of the support material. However, the smaller the diameter of the support material, the more expensive it may be, depending on the amount of polishing required to produce the desired size. In addition, the smaller the diameter of the support material, the more fluid flow channels can be disturbed by the concentrate added to the top of the bottom. Larger support materials allow higher hips to form without the risk of clogging the flow channel.

Typically, the support material will be greater than about 0.62 cm in diameter and less than about 2.54 cm. Preferably the diameter of the support material is greater than about 0.95 cm and less than about 1.9 cm. The support material with a diameter of about 1.27 cm will be the optimal size.

To biooxidize the concentrate, the bottom is inoculated with bacteria or other microorganisms capable of biooxidizing sulfide minerals in the concentrate. Such microbial treatments are well known in the art. Bacteria that can be used for this purpose include Thiobacillus ferrooxidans , Leptospirillum ferrooxidans and Thiobacillus thiooxidans . Thiobacillus ferrooxydans are particularly preferred microorganisms for biooxidation processes.

If the bioleaching solution is recycled, a preliminary step may be necessary to prevent the generation of toxic substances in the recycled solution to prevent the biooxidation rate from becoming too slow. The process described in US patent application Ser. No. 08 / 329,002, filed Oct. 25, 1994, can be used to ensure that inhibitory substances are not produced until they are detrimental to the biooxidation process.

After the refractory sulfide concentrate is sufficiently biooxidized, the free precious metals can be leached with a thiourea or cyanide leaching agent. Cyanide is a preferred leachant even if the pH of the hip has to be raised first before leaching. The advantage of thiourea is that it is not toxic to biooxidized microorganisms. As a result, intermittent leaching may be performed to dissolve free noble metals and resume the biooxidation process.

The dissolved precious metals can be recovered from the leach agent using techniques well known to those skilled in the art, such as carbon during leaching and carbon during column processing.

Another advantage of the method is that it can be used continuously by adding intermittently fresh or fresh concentrate to the top of the heap. The advantage of adding a new concentrate to the top of the heap is that once the heap is completed and biooxidation occurs rapidly, the rate of biooxidation in the heap is not required to destroy the heap to add new concentrate to treat the biooxidized material. Can be kept high.

Due to the relatively low capital and operating costs of the process according to this aspect of the invention, it can be used to economically process very low concentrates, and consequently to process lower ores than milled biooxidation processes. In addition, a good fluid flow (both air and liquid) is ensured in the heap by spreading a concentrate of the noble metal containing refractory sulfide mineral on top of the bottom of the support material.

Another aspect of the invention is now described. In this aspect of the present invention, a method of recovering base metals from sulfide ores is provided. Such ores include, for example, chalcopyrite, zinc zinc, nickel sulfide ores and uranium sulfide ores. The process according to this aspect of the invention comprises (a) producing a sulfide mineral concentrate consisting of fine metal sulfide particles, (b) distributing the concentrate over the bottom of the coarse support material, and (c) biooxidizing the concentrate. And (d) recovering the useful metals from the solution used to biooxidize the metal sulfide mineral. This process uses a heap of coarse support material as a bioreactor, similar to the method described in connection with this aspect of the present invention for the treatment of concentrates of noble metal containing sulfide minerals, whose capital and operating costs are milled organisms. Less than that of the leaching operation. However, because of good airflow at the bottom, the rate of biooxidation of sulfide minerals is very high and can be close to the rate observed in milling operations.

Nonmetals that can be recovered from the process according to this aspect of the invention, depending on the sulfide ore from which the concentrate has been obtained, include copper, zinc, nickel and uranium.

Process parameters and considerations for the process according to this aspect of the invention are as described above for this aspect of the invention for processing precious metal containing concentrates of refractory sulfide minerals. The main difference between the two methods, however, is that the base metals of interest in this method dissolve during the biooxidation process. As a result, useful metals can be recovered directly from the solution used to biooxidize the concentrate of the metal sulfide mineral. The technique used to extract useful metals of interest from bioleachers will depend on the particular metal in question. As will be appreciated by those skilled in the art, such techniques will include precipitation through solvent extraction, iron tritan and pH adjustment. Solvent extraction is a particularly preferred method of removing copper from the bioleaching solution.

In the process according to this aspect of the invention, the process can be operated continuously by intermittently adding the concentrate. For example, the concentrate may be added on a daily or weekly basis. As noted above, due to such additions, the biooxidation rate remains high for concentrates that are distributed to the hips and move through the hips.

As will be appreciated by those skilled in the art, the method according to this aspect of the present invention may be combined with the method according to this aspect of the present invention for recovering precious metals from concentrates of refractory sulfide minerals. This is because non-metals obtained from refractory sulfide minerals will be dissolved into the bioleaching solution during the biooxidation process while releasing occluded precious metals contained in the sulfide minerals. These can then be recovered using the techniques described above if desired.

Several aspects of the invention, which are preferred embodiments of the invention described above, will be described in more detail in the following examples. Such details are intended to illustrate the invention disclosed herein and are not intended to limit the invention to the embodiments described.

Example 1

Low grade (3.4 ppm) gold ore samples known to be refractory to leaching by cyanide due to sulfides were ground. The ore was separated into -0.62 cm fractions (47.4 wt%) and -0.31 cm fractions (rest). The -0.31 cm fraction was then ground through a 75 μm sieve to 95% to assist in the production of refractory pyrite concentrates by flotation.

Water was added to the polished samples until the 30% pulp density was reached. The ore pulp was then adjusted to pH 10 and treated with 6 kg of Na ₂ SiO ₄ per tonne of ore for 12 hours to remove clay material. The clay material was removed into unsedimented fractions after 12 hours.

Since clay can cause problems in the flotation phase, a step to allow non-clay material to settle was added for removal of the clay fraction before the flotation phase of the sample.

The clay fraction contained less than 3% of the total ore weight, but contained almost 5% of the gold in the ore. Removal of the clay fractions and subsequent flotation steps resulted in very small fractions (0.1% of the total ore weight), but contained at least 17 ppm of gold. Cyanide leaching of clay suspended residues extracted more than 76% of the gold contained. The total amount of gold in the clay floc was 1.08 ppm.

Prior to the floating step, the main fraction of polished ore (+5 μm to -75 μm) was mixed in a Wemco suspended cell and adjusted to 2.0 kg / ton of CaSO ₄ for 10 minutes. This process was performed by mixing with 100 g / ton of xanthate for 10 minutes and then with 50 g / ton of Dowfroth D-200 for 5 minutes. The sample was then suspended for 20 minutes at a pulp density of 30%. 4 kg of the main fractions were treated in eight separate batches of 500 g each. Sulfide concentrates obtained from these flotation steps were collected and combined and resuspended in a column.

Three fractions, residues from Wemco float, residues from column floater, and sulfide concentrates were dried and sedimented respectively. The debris from the Gecko suspension was 35.4% by weight of the total ore weight and contained 1.88 ppm gold. The gold yield by cyanide leaching of the fraction was 67%. This is higher than the recovery during cyanide leaching of the total ore, which was 63%. The column residue contained 3.56 ppm gold. Gold recovery from the fraction by cyanide leaching was 76.6%.

The sulfide concentrate was 753 g weight, 8.8% of the total ore (+0.31 cm and -0.31 cm fractions). Analysis of a small fraction of the concentrate showed that it contained 6.5 ppm of gold. The fraction was coated on 47.4% by weight of +0.31 cm ore. The dry pyrite concentrate was sprayed onto the surface of the ore by rolling in a drum rotating at 30 rpm while spraying a mixture of 2,000 ppm ferric ions and a 1% Nalco # 7534 mixture, which was an aggregate. The pH of the solution was 1.8.

The concentrate mixture on the crude ore support was placed in a 7.62 cm column. Air and liquid were introduced from the top. The column was inoculated with 10 ml of thiobarcillus ferrooxidans bacteria at a bacterial concentration of about 1.1 × 10 ¹⁰ per OD 2.6 or 1 ml.

The bacteria were incubated in acidic nutrient solution containing 5 g / l ammonium sulfate and 0.83 g / l magnesium sulfate heptahydrate. The pH of the solution was adjusted to sulfuric acid (H ₂ SO ₄ ) and maintained in the range of 1.7 to 1.9. The solution also contained 20 g / l iron in the form of ferric sulfate and ferrous sulfate.

After the pH was adjusted to 1.8, bacteria were added to the top of the column. The liquid introduced at the top of the column during the experiment was a liquid of pH 1.8 with 0.2 x 9 K salt and 2,000 ppm of ferric iron. The degree of iron oxidation was determined by subtracting iron introduced by the 2,000 ppm ferric feed from the analysis of the solution eluting from the column.

The composition of the standard 9K salt medium for thiobacilli ferrooxydans is shown in the table below. Concentrations were given in g / l.

(NH ₄ ) SO ₄ 5 KCl 0.17 K ₂ HPO ₄ 0.083 MgSO _{4 7} H ₂ O 0.833 Ca (NO ₃ ) .4H ₂ O 0.024

0.2 × 9 K salt indicates that the 9 K salt solution concentration was 20% of the standard 9 K salt medium concentration.

After 60 days, the amount of iron leached from the column indicated that about 50% of pyrite was biooxidized. The experiment was terminated and the mixture was separated into +600 μm fraction and -600 μm fraction. Each fraction was polished to 95% -75 μm and then leached by 96-hour bottle roll analysis using a 500 ppm cyanide solution. Activated carbon was added to the bottle roll test to absorb undissolved gold.

The gold recovery of the -600 μm fraction was 83.7%. The -600 μm material showed an increased surface gold value of 8.87 ppm due to the loss of pyrite weight. On the other hand, the crude +600 μm fraction showed 57% gold recovery and 2.27 ppm surface gold. This means that the concentrate pyrite coated on the surface of the crude rock biooxidized faster than the crude fraction of the rock.

Example 2

Another comparative test was done. In this example, biooxidation rates of ore size fractions were compared. Ore from Ramrod Gold Corporation was ground to 1.9 cm. The -0.31 cm ore fraction was removed and used to form the concentrate. The ore sample had less than 2.7 g (2.7 ppm) of gold per tonne of ore. The sample contained both ferrous ores and pyrites. The concentrate was made by ball milling until 5 kg of -0.31 cm ore passed through -75 μm, and the ball milled ore was flocculated with xanthate to form pyrite concentrate. Prior to the flotation step, the clay was removed by sedimentation with 6 kg of Na ₂ SiO ₄ per tonne of ore for at least 8 hours. Suspension steps were performed in small batches of 500 g each in a laboratory Gecko suspension cell. Potassium amyl xanthate was used at a concentration of 100 g / ton as a collecting agent, with 1.5 kg / ton of sodium sulfide and 50 g / ton of Dowforce D-200. The pyrite concentrate made up 4.5 wt% of the -0.31 cm ore fraction. However, this ore fraction contained at least 80% gold and pyrite for milled ores. The concentrate contained about 17.4% iron, 15.7% sulfur and about 40 ppm gold. The +0.31 cm ore contained 0.9% iron and 0.18% sulfur.

A 140 g sample of the concentrate was coated onto 560 g of +0.31 cm light ore. The concentrate was added to the ore as dry powder. The mixture was then rotated at 30 rpm in a small plastic drum to spread the dry concentrate onto the rock support. A liquid containing 2,000 ppm ferric ions and 1% Nalco # 7534 was sprayed onto the mixture until all concentrates were coated on rock. The pH of the solution was maintained at 1.8. The amount of liquid used was determined to be 5 to 10 wt% of the weight of the ore and concentrate. The 700 g mixture of concentrate on the crude ore substrate was transferred to a 7.62 cm column. The ore's height was about 12.7 cm after being placed in the column. Air and liquid were introduced from the top of the column. A column of concentrate coated on the ore substrate was inoculated with about 10 ml of OD 2.0 or 8 × 10 ⁹ bacteria per ml.

Bacteria were mixed cultures of thiobacilli ferrooxydans starting with ATCC # 19859 and 33020 strains. The bacteria were incubated in acidic nutrient solution containing 5 g / l ammonium sulfate and 0.83 g / l magnesium sulfate heptahydrate. The pH of the solution was adjusted to sulfuric acid (H ₂ SO ₄ ) and maintained in the range of 1.7 to 1.9. The solution also contained 20 g / l of iron in the form of ferric sulfide and ferrous sulfide.

After the pH was adjusted to 1.8, bacteria were added to the top of the column. The liquid introduced at the top of the column during the experiment was a liquid of pH 1.8 with 0.2 × 9 K salt and 2,000 ppm of ferric ions. The degree of oxidation of iron was determined by subtracting the amount of iron introduced by the 2,000 ppm ferric feed from the analysis of the solution eluting from the column.

This ore had a low sulfide content at concentrations below 1% of its own weight. When the concentrate was prepared for the crude rock at 20% by weight, the concentration of pyrite and gold could be increased more than 10 times. This increased the biooxidation rate relative to the total ore as shown in FIGS. 6 and 7. In addition to exposing more pyrite to air and water, the process also increased the amount of ferric ions and acids generated per unit volume of ore in the column model with respect to the heap.

FIG. 6 shows the amount of oxidation determined by% leached iron on both the pyrite concentrate of the ore and the total ore itself on a +0.31 cm ore. As shown in the graph, the concentrate process biooxidized about 40% within the first 30 days and at least 65% within the first 60 days. In contrast, only 24% of all ores were biooxidized within 84 days. The average daily biooxidation rate is shown in FIG. The highest daily average biooxidation rate of the coated concentrate was 1.8% per day, compared to only 0.5% of the average daily biooxidation rate of all ores. As shown in FIG. 7, the coated concentrate sample did not take a long time to start biooxidation. This means that the coated concentrate process is easy to achieve complete biooxidation in a fairly short time.

Table 1 below shows the specific data points graphed in FIGS. 6 and 7 of the concentrate process on the crude ore and the overall ore process performed for the comparative experiments.

After 68 days the concentrate coated on the ore column decomposed. Biooxidized material was separated into +180 μm fraction and -180 μm fraction. The amount of fine material increased from 140 g to 150 g. The total amount of iron removed from the system for 68 days of biooxidation is 21.5 g, expressed as pyrite 46 g. The weight of the crude rock decreased by 54 g. This is believed to be due to the decomposition of the rock into finer materials due to the biooxidation process. The total weight after biooxidation was 656 g, 44 g smaller than the starting material. This is in good agreement with the calculated 46 g of oxidized pyrite.

Concentrate process Whole ore process Days Leached iron% Iron / day Days Leached iron% Iron / day 0 0.0 0.00 0 0.0 0.00 9 8.4 0.93 13 0.2 0.01 16 18.5 1.44 21 2.5 0.29 20 25.5 1.76 28 5.1 0.38 23 31.0 1.82 35 8.6 0.50 28 37.5 1.30 42 11.7 0.44 33 41.7 0.84 49 13.8 0.29 37 46.1 1.10 56 15.9 0.31 43 51.8 0.95 62 18.4 0.42 51 60.7 1.11 70 21.5 0.39 58 66.7 0.86 77 23.1 0.23 65 70.9 0.60 84 24.3 0.16

Two samples of -180 μm material and one +180 μm material were leached with cyanide. To leach the samples, a bottle roll was run for 96 hours and the leach solution was maintained at 500 ppm cyanide. The +180 μm light ore support rock was polished to -75 μm 95% before running the bottle roll. All bottle rolls were done using activated carbon in the leaching solution.

Analysis of the -180 μm fraction of sulfides after 68 days of biooxidation showed that the sample still contained 8.8% cyanide, 56% of the initial level. This was a lower% oxidation than indicated by leached iron during the column experiment. Gold recovery was increased to 84.3% for the -180 μm high (38 ppm) fraction and 79.5% for the +180 μm low (3 ppm) fraction. This is a significant increase over 45.6% recovery of unoxidized ore.

Example 3

Sulfide suspension concentrates were made using 70% -75 μm gold ore samples from the Dominican Republic mine. Ore samples were obtained from piles of waste from mines already leached with cyanide. The ore sample still contained more than 2 g / tons of gold that was blocked in sulfides and could not be leached directly by cyanide.

To form sulfide concentrates, several kg of the sample were further ground to 95% -75 μm. This polished sample was suspended to form a sulfide concentrate. Suspension steps were performed in small batches of 500 g each in a laboratory Gecko suspension cell. Prior to flotation, the polished ore sample was adjusted to a pulp density of 30%. The ore slurry was mixed at pH 8.5 for 5 minutes with 1.5 kg / ton of sodium sulfide (Na ₂ S). Potassium amyl xanthate as a collecting agent was then added at 100 g / ton and mixed for 5 minutes. 50 g / ton of Dowforce D-200 was then added and mixed for 5 minutes. Finally, air was introduced to produce a sulfide concentrate comprising 17.4 wt% iron and 19.4 wt% sulfide and 14 g of gold per tonne of concentrate. A plurality of coated substrates were made by coating 140 g of sulfide concentrate on +0.31 cm to -0.62 cm granite. The concentrate was added to the granite as a dry powder. The mixture was then rotated at 30 rpm in a small plastic drum to spread dry pyrite over the support material. Liquid containing 2,000 ppm ferric ions and 1% Nalco # 7534 flocculation aid was sprayed onto the mixture until all concentrates were coated on wet granite. The pH of the solution was maintained at 1.8. In this case, the rock has no iron or gold. However, rocks not only contained small amounts of mineral carbonates that initially kept the pH high, but also provided the bacteria with CO ₂ as a carbon source.

700 g of concentrate coated rock was added to the column. A 2,000 ppm ferric ion solution with 0.2 × 9 K salt and a pH of 1.6 was introduced from the column top at a flow rate of about 300 ml / day. The column was then inoculated with 10 ml of bacteria as in Example 2. The pH of the concentrate coated rock substrate was adjusted to pH 1.8 and the pH of the influent was set to 1.8. In addition, air was injected through the top of the column.

8 is a graph showing the biooxidation rate determined by% iron leached from the concentrate. The average daily percentage of biooxidation was calculated and shown in Table 2 and graphically shown in FIG. 9. The% biooxidation rate was determined by dividing the total iron removed by the total iron contained in the concentrate. Biooxidation rates started slowly with adjustment of pH and growth and adaptation of bacteria. However, after about two weeks, the biooxidation rate increased rapidly and peaked after 30 days. By this time, nearly 50% of all iron was biooxidized. This process continued with slowing down as the remaining pyrite was consumed. Nearly 64% of iron was biooxidized after 64 days. In the second half of the process, the concentrate was almost completely biooxidized and the rate of biooxidation slowed down, but the average daily biooxidation rate was still around 1% / day. After 70 days, biooxidation was stopped. Biooxidized concentrate was separated into +180 μm fraction and −180 μm fraction. The amount of biooxidized concentrate was reduced from 140 g to 115 g. The total amount of iron removed from the system during the 70 days of biooxidation was 25.9 g, meaning 55.5 g of pyrite. The weight of granite was reduced by 98.9 g. This is believed to be due to the breakdown of calcium carbonate in the rock by acid and the breakdown of the rock into finer materials. The total weight was reduced by 123.3 g, which was 67.8 g more than would be predicted by biooxidation of pyrite alone.

Days % Bio-oxidation % Biooxidation / Day 5 2.590 0.288 15 10.270 1.100 22 24.970 2.100 27 37.250 2.450 32 49.700 2.490 36 58.610 2.230 42 68.580 1.660 50 82.580 1.750 57 90.870 1.180 64 96.820 0.850

A sample of -180 μm material was leached for 96 hours in a bottle roll using 500 ppm cyanide. The +180 μm granite was also leached with 500 ppm cyanide to determine how much gold could stick to the support in this process using waste rock as a support substrate. Analysis of the -180 μm material still contained 9.7% of sulfides, representing only about 50% oxidation.

The gold extraction rate was 77% at -180 mu m. Since this gold is recovered from gold ore pre-leached with cyanide, it can be seen that the process according to the invention can be used for ore which has been considered waste until now. In addition, although the recovery is higher than any process currently being carried out in the mine, the process according to the invention was able to recover 77% gold even from what was previously considered waste.

Leaching the granite support rock with cyanide produced 0.15 ppm of gold, 3.4% of the total gold.

Example 4

Gold samples containing refractory sulfides ground to pass 80% through 0.62 cm were prepared for testing as support rock. The ore was obtained from a Western State mine in Nevada, USA, containing a high concentration of carbonate mineral in the form of limestone. Fine material (0.31 cm or less) was removed to improve air flow. Four kg of +0.31 cm to -0.62 cm rock samples were coated with 1 kg of gold containing pyrite concentrates provided by other mining companies. The coating placed the ore substrate and the dry concentrate into a small rotating drum and contained 2,000 ppm ferric ions and 1% Nalco # 7534 flocculation aid in the mixture until all sulfide concentrates were coated on the wet granite stone. The liquid was formed by spraying.

Iron analysis of both samples revealed that the concentrate contained 4 kg of support rock containing 210 g of iron and 42.8 g of iron.

5 kg of coated ore substrate was placed in a 7.62 cm column. To begin the biooxidation process, a solution, pH 1.3, containing 2,000 ppm of ferric ions was passed through the column at about 1 liter per day. After 7 days, the pH of the solution leaving the column was 2.5 or less. At this point, the column was inoculated with 10 ml of Thiobacillus ferrooxydans bacteria (as in Example 2) and the pH of the feed was increased to 1.8. After a total of 15 days the column was producing acid at pH 1.7 and 700 mV Eh. The progress of the biooxidation process was determined by measuring iron leached from the column of concentrate coated nominal 0.62 cm ore. The data were compared with results from experiments in which the same concentrates were coated on samples of obsolete rock. The leaching rates of the two cases were compared in the graph form of FIG. 10. The fact that western state experiments are rather fast can be argued that the mineral support rocks also oxidize to some extent.

Western state column experiments were performed for a total of 74 days, leaving a total of 166 g of iron or 66% of the total iron in the concentrate and support rocks out of the system. Most of the iron was leached in the concentrate, but some also occurred in the support rocks. After biooxidation the weight of the concentrate decreased from 1,000 g to 705.8 g. 4 kg of western state ore support rock was reduced to 3695.5 g, indicating that 304.5 g or 7.6% of its weight was lost after biooxidation. The decrease in light ore support rock weight was due to the combined factors of biooxidation of pyrites, acid leaching of carbonates in the ores and physical polishing in the ores.

705.8 g of biooxidized concentrates from other mines in Nevada, USA were tested for gold extraction using the cyanide bottle roll test. Gold recovery before biooxidation was 46%. After biooxidation, the gold extraction rate increased to 86%. Such gold recovery was achieved by biooxidizing the concentrate equally for the gravel support material.

Acid consumption of Western State Ore was measured before and after being used as a support rock for biooxidation. The amount of sulfuric acid required to adjust to below pH 2 before biooxidation was 31.4 g per 100 g of ore. The amount of acid required to adjust the pH below 2 after biooxidation was 11 g per 100 g of ore. This means that about 20% of the weight of the support rock is an acid that is neutralized for 74 days of biooxidation. It was more than 7.6% loss of support rock weight. This may be due to sample-to-sample variation in% of precipitate or limestone formed in the rock after biooxidation.

Several conclusions can be drawn from this test. Firstly, a low pH biooxidation process can take place on the high carbonate ore surface. Secondly, with the +0.31 cm to -0.62 cm support material, the neutralization process with pH 1.8 acid is slow enough that the carbonate in the ore is still not completely removed after 74 days. The slow acid neutralization process is useful for bacteria because neutralization of limestone in the ore can provide the carbon dioxide gas needed to biooxidize the bacterial carbon source. Third, the crude ore support is useful from this method because smaller non-suspended sulfides in the western state ore are biooxidized.

Based on the neutralization amount of the +0.31 cm to -0.62 cm ore support occurring within about 2 months, the +0.62 cm to -1.9 cm ore support rock was best for the front face process. Larger ore support will take 90-120 days for the bottom biooxidation process to best utilize limestone neutralization and also to biooxidize smaller suspended sulfides in the ore support rock. The time to biooxidize the coating of sulfides sprayed on the outer surface of the ore support is generally no more than 90 days. Thus, the ore support may be polished and suspended several times before making pyrite concentrates for biooxidation at the surface of the ore support rock.

Prior to biooxidation, two attempts have been made to produce concentrates by flotation of western state ores. One method was to use only xanthate, producing a low gold recovery of less than 12% in pyrite concentrates. The debris from the flotation still contained 4.0 g Au / ton. The extraction of suspended beneficiation residues by cyanide recovered only 17% of the gold remaining in the residues.

The second attempt in flotation has used kerosene to flotation from carbon concentrates and then xanthate to produce pyrite concentrates. The combined weight of the concentrate was calculated as 18% by weight of the ore, which was twice the 7.4% by weight concentrate produced using xanthate alone. Combined gold recovery of the two concentrates increased to 53.8% gold. The debris from the flotation decreased to 2.12 g / ton of gold. Extraction of the residue by cyanide recovered only 34.5% of the gold remaining in the residue after flotation of the two concentrates.

A third attempt at floating beneficiation was made with Western State Ore after being used as support rock for biooxidation in this example. The ore substrate from +0.31 cm to -0.62 cm was ground to -75 μm and then suspended using xanthate as a collecting agent. This formed a pyrite concentrate of 33.4 g Au / ton and 7.9% by weight of the ore. The flotation in the flotation contained 1.09 g Au / ton. Gold recovery to pyrite concentrate was 72.4%. Cyanide extraction of 1.09 g / ton residues recovered 48.7% of gold to yield 0.56 g / ton of final tail.

33.4 g Au / ton pyrite concentrate was biooxidized in shake flask experiments. Cyanide extraction after biooxidation increased the yield to 99%. This result indicates that the concentrate was a gold containing pyrite which could be biooxidized with other concentrates in the coated substrate process.

As can be seen from the flotation results included in Table 3 below, by flotation of the Western State ore after use as a support material for biooxidation, higher pyrite concentrates were produced more easily, and flotation flotation was It was less fire resistant to cargo extraction. This may be due to chemical conversion to pyrite for 74 days at high iron and low pH biooxidation conditions. In contrast, non-suspended sulfides may have become less fire resistant due to the combined factors of ferric and bacterial oxidation.

Flotation beneficiation results First pyrite floating Second float Suspension after tertiary biooxidation smash -75 μm -75 μm -75 μm Flotation Beneficiation Reagent Xanthate, Dow Pros Kerosene, NaSiO ₃ , Xanthate, Dow Prosper NaS, CuSO ₄ , Xanthate, Dow Prosper Pyrite concentrate wt% 7.4% 3.2% 7.9% Carbon Concentrate Weight% - 14.8% - Concentrate Gross Weight% 7.4% 18.0% 7.9% Concentrate grade 6.4 g / ton 26.4 g / ton 33.4 g / ton Gold% in concentrate 11.3% 53.8% 72.4% Gold in residue before CN extraction 4.0 g / ton 2.12 g / ton 1.09 g / ton Gold in residue after CN extraction 3.32 g / ton 1.39 g / ton 0.56 g / ton Gold recovery from leach leaching by CN 17.2% 34.5% 48.7% Combined Total Recovery 26.4% 69.2% 85.4% Head grade of the tested sample 4.18 g / ton 3.77 g / ton 3.64 g / ton

Example 5

Two simultaneous bioleaching tests were set up to test the biooxidation rate of gold containing ore pyrite concentrates. The first consisted of a column type experiment simulating the bottom leaching process, and the second consisted of a shake flask test simulating the stirred tank method.

Both starting concentrates were obtained from the Jamestown mine in Tuolum County, California, USA. The mine was owned by Sonora Gold Corporation and located along the circular vein system. The concentrate was produced using a xanthate flotation process and contained 39.8% sulfide and 36.6% iron. Sulfide minerals in the concentrate mainly contained pyrite. Size analysis showed that at least 76% of the concentrate particles were less than 75 μm. The concentrate has a high gold concentration (about 70 g per tonne of concentrate) and is known to be fire resistant to cyanide leaching.

The biooxidation rate in each test was determined by analyzing the iron concentration in all solutions removed from the column, or in the case of a flask test, by adding the iron solution removed in solution.

Cultures of thiobacillus ferrooxydans were used to biooxidize sulfide mineral concentrates in each test. Thiobacillus ferrooxydans cultures were induced starting with ATCC strains 19859 and 33020. Cultures had a pH of 1.7 to 1.9, 5 g / l ammonium sulfate ((NH ₄ ) ₂ SO ₄ ), magnesium sulfate heptahydrate (MgSO ₄ · 7H ₂ O) 0.833 g / l, and ferrous or ferrous sulfate Cultured in acidic nutrient medium containing 20 g / l iron in the form of iron. The pH of the solution was adjusted within this range using sulfuric acid (H ₂ SO ₄ ).

Prior to adding the culture to the test sample, a mixed culture of bacteria oxidizing sulfide minerals was incubated with a cell density of 4 × 10 ⁹ to 1 × 10 ¹⁰ cells per ml.

The column experiment was started by inoculating 150 g of concentrate sample with about 10 ⁸ cells per g of concentrate. This was done by adding 3 ml of 5 × 10 ⁹ bacteria per ml to 150 g sample of pyrite concentrate. 150 g of pyrite concentrate suspension was then poured into a column of 7.62 cm x 1.83 meters which was half filled with 3 L of 0.95 cm lava. Lava rock support materials were chosen because they have a high surface area and withstand the acidic conditions encountered during biooxidation.

During inoculation and solution addition, the pyrite concentrate was not washed out of the column. Most pyrite concentrates were attached to the first 30 cm of lava rock. Air and solution were introduced through the column top. The bioleaching solution was recycled until the column pH dropped to about 1.8. After biooxidation initiated in the column, a 0.2 × 9 K salt solution containing pH 1.8 and 2000 ppm of iron, mainly in the form of ferrous iron, was fed to the column. 2000 ppm iron was excluded from all iron analyses in the solution from the column.

After 26 days of biooxidation, about 35% of iron in the pyrite concentrate was oxidized. At this point, the test was converted to a continuous process test by adding 3 g of fresh concentrate to the column daily. After nine more days, the addition rate of pyrite was increased to 6 g / day.

The flask test was started in the same way as the column test. To begin the experiment, 50 g of pyrite concentrate sample was inoculated with 1 ml of bacterial culture. The pyrite concentrate was then added into a large shake flask with 1 L of 0.2 x 9 K salt solution with pH 1.8. The concentrates were inoculated with the same bacteria as well as the same bacteria per gram.

Air was introduced into the bioleaching solution at 250 rpm by orbital shaking of the flask. The solution was removed from the flask over time to maintain the concentration of ferrous iron so as not to be much higher than in the column.

When the column experiment was converted to a continuous process on day 26, the flask experiment was also converted to a continuous test by adding 1 g / day pyrite concentrate to the flask. After nine more days, the amount of concentrate added was increased to 2 g / day.

After 58 days, pyrite addition was stopped in both flask and column experiments. Both columns and flasks were allowed to undergo biooxidation for an additional 20 days. At this point, the concentrate in the column was about 76% oxidized and the concentrate in the flask was about 89% oxidized. The column was then leached with thiourea for 10 days to extract the dissociated gold. Thiourea extracted only about 30% of gold. However, three days after the addition of 0.2 × 9 K salt solution having a pH of 1.8 and containing 2,000 ppm of ferric ions, the iron concentration of Eh and the column effluent increased. This indicates that thiourea is nontoxic to bacteria and that thiourea extraction could be performed over time without killing the bacteria.

FIG. 11 shows biooxidation over days in both cases of column and flask concentrate bioleaching tests. The “TU leaching” paragraph in FIG. 8 means thiourea leaching. The data used to fabricate FIG. 8 is shown in Tables 4 and 5 at the end of this example.

As indicated above, the flask was for simulating a stirred tank process. When the flask test was converted to a continuous process by adding pyrite daily, it would simulate a large-sized process of intermittently introducing new pyrite into a rapidly biooxidizing tank containing a large amount of bacteria adapted to the ore. Iron pyrite was added daily to the column to test the feasibility of a continuous process of continuously or intermittently adding precious metal containing sulfide minerals to the top of a heap of biooxidative concentrates distributed over a support material heap such as limestone.

As demonstrated in the above test, the biooxidation rate was not significantly different between the column and flask tests. The onset of biooxidation was a bit slow in the column test. This may be due to a delay of about 10 days for the pH of the column to drop to 1.8. The biooxidation rate of the column then becomes like a flask. Later in the experiment, biooxidation rate begins to slowly decrease again. This may be due to the lack of mixing of biooxidizing pyrite and new pyrite. However, the biooxidation rate between the two tests is close enough to demonstrate the feasibility of the method according to the invention. The feasibility of the method of the present invention is very useful in terms of very low capital costs in the bottom process and operating costs of the process compared to stirred tank processes.

Although the present invention has been described using preferred embodiments and specific examples, it will be readily understood by those skilled in the art that many modifications and applications of the present invention are possible without departing from the technical awards and scope of the invention as claimed below. For example, although the methods according to the invention have been described in terms of recovery of gold from refractory sulfide or refractory carbonaceous sulfide ores, the method of the invention is equally applicable to other precious metals such as silver and platinum. Similarly, the method according to the invention can be used to biooxidize sulfide concentrates from metal sulfide ores such as brass ores and zinc ore as readily recognized by those skilled in the art.

Claims (86)

(a) coating a surface of a plurality of coarse substrates having a particle size greater than about 0.3 cm with a solid material to be biotreated to a particle size of less than about 250 μm containing unwanted compounds to form a plurality of coated coarse substrates. step, (b) stacking said plurality of coated coarse substrates in a heap or placing said plurality of coated coarse substrates in a tank to form a counter surface surface reactor with an empty space of at least about 25%. , (c) inoculating the reactor with a microorganism capable of degrading unwanted compounds present in the solid material, thereby forming a counter surface bioreactor, and (d) biotreating the solid material in the bioreactor until the unwanted compound in the solid material decomposes to the desired concentration. A method of biotreating a solid material using a comparative surface bioreactor to remove unwanted compounds comprising a. The method of claim 1, further comprising: (e) separating the biotreated solid material from the plurality of coarse substrates after the unwanted compound has been degraded to the desired concentration and (f) repeating steps (a) through (d) using the plurality of coarse substrates How to further include. The method of claim 1 wherein said unwanted compound is an organic pollutant. The method of claim 3, wherein the solid material is soil. The process of claim 4 wherein the organic contaminants are waste oil, grease, jet fuel, diesel fuel, crude oil, benzene, toluene, ethylbenzene, xylene, polyaromatic hydrocarbons (PAH), polynuclear aromatics (PNA), pentachlorophenol (PCP). ), Polychlorinated biphenyl (PCB), creosote, insecticide, 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octa With hydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocin (HMX), N-methyl-N-2,4,6-tetranitroaniline, and nitrocellulose (NC) At least one selected from the group consisting of: The method of claim 3, wherein the plurality of coarse substrates are made of plastic. The method of claim 1 wherein said unwanted compound is a sulfide mineral. 8. The method of claim 7, wherein said solid material is coal. The method of claim 8, wherein the plurality of coarse substrates consists of coarse coal particles. 8. The method of claim 7, wherein said solid material is a refractory sulfide ore. The method of claim 10, wherein the plurality of coarse substrates consist of refractory coarse sulfide ore particles. The group of any of claims 1, 2, 3, 4, 5, 7, 8, and 10, wherein the plurality of coarse substrates consist of rock, volcanic rock, gravel, carbonate mineral containing rock, brick, concrete block, and slag. And at least one substance selected from. The method of claim 1, wherein the nominal particle size of the coarse substrate is from about 0.6 cm to about 2.54 cm. The method of claim 1, wherein the amount of solid material coated on the plurality of coarse substrates is from about 10% to about 30% by weight. The method of claim 1, wherein the particle size of the solid material is at least about 25 μm. The method of claim 1, wherein the nominal particle size of the solid material is between 75 μm and less than 106 μm. The method of claim 1, wherein the biotreatment step is Supplying the bioreactor with the nutrients necessary to maintain the growth of the microorganisms, maintaining the moisture content of the bioreactor above the desired level, blowing air into the bioreactor through the porous tube, preliminary pH of the bioreactor Maintaining at a predetermined range, maintaining the temperature of the bioreactor at a predetermined range. The method of claim 1, wherein the thickness of the solid material coating on the plurality of substrates is less than about 1 mm. The method of claim 1, wherein the void space is at least about 35%. The method according to claim 1, wherein the coarse substrate has a particle size of less than 0.3 cm of 5 wt% or less. The method of claim 1 wherein the solid material is a sulfide mineral concentrate comprising fine metal sulfide particles containing a desired useful metal, wherein the unwanted compound is the fine metal sulfide particles and coated on the surface of the substrate. And wherein the biotreatment of the sulfide mineral concentrate is biooxidized until the fine metal sulfide particles in the sulfide mineral concentrate are biooxidized by the desired amount to free the desired useful metal. The method of claim 21, wherein the control surface reactor is formed by stacking coarse substrates coated with a plurality of concentrates with heaps, (e) biooxidizing the desired amount of fine metal sulfide particles coated on the surface of the plurality of coarse substrates and then destroying the hips, (f) separating the biooxidized fine metal sulfide particles from the plurality of coarse substrates, and (g) further comprising repeating steps (a) through (d) using this plurality of coarse substrates. The method of claim 21, wherein the control surface reactor is formed by placing a coarse substrate coated with a plurality of concentrates in a tank, (e) separating the biooxidized fine metal sulfide particles from the plurality of coarse substrates, and (f) further comprising repeating steps (a) through (d) using this plurality of coarse substrates. 22. The method of claim 21, wherein the plurality of coarse substrates consist of ore particles containing metal sulfide particles. The method of claim 24, (e) biooxidizing the metal sulfide particles coated on the surfaces of the plurality of coarse substrates by a desired amount, and then separating the biooxidized fine metal sulfide particles from the plurality of coarse substrates, (f) grinding the plurality of coarse substrates to a particle size sufficient to separate metal sulfide particles from the plurality of coarse substrates, (g) producing a second sulfide mineral concentrate comprising fine metal sulfide particles from the plurality of milled coarse substrates, (h) coating the plurality of second coarse substrates with a second concentrate, (i) forming a second heap using a plurality of second coating substrates, and (j) biooxidizing a second concentrate of fine metal sulfide particles How to include more. The method of claim 24, wherein the ore particles also comprise mineral carbonate. 22. The method of claim 21, wherein the material used for the plurality of coarse substrates is one or more materials selected from the group consisting of volcanic rock, gravel and mineral carbonate containing rock. 28. The method of any one of claims 21-27, wherein the coarse substrate has about 0.6 cm to 2.5 cm nominal particle size. 28. The method of any one of claims 21-27, wherein the amount of coated concentrate on the plurality of coarse substrates is from about 10% to about 30% by weight. 28. The method of any one of claims 21-27, wherein the concentrate comprises at least about 20% by weight metal sulfide particles. The method of claim 21, wherein the concentrate comprises at least about 40% by weight metal sulfide particles. The method of claim 21, wherein the concentrate comprises at least about 70% by weight of metal sulfide particles. 28. The method of any one of claims 21 to 27, wherein the concentrate comprises 40 to 80 weight percent of metal sulfide particles. The method of claim 21, wherein the concentrate has a particle size of greater than about 25 μm. The method of claim 21, wherein the particle size of the concentrate is less than about 106 μm. The method of claim 21, wherein the nominal particle size of the concentrate is less than about 75 μm. 28. The method according to any one of claims 21 to 27, wherein the desired useful metals are one or more precious metals selected from the group consisting of gold, silver and platinum. 28. The method of any one of claims 21 to 27, wherein the desired useful metals are base metals obtained from metal parts of metal sulfide particles. The method of claim 1, wherein the solid material is a sulfide mineral concentrate comprising fine metal sulfide particles containing occluded precious metals, and the unwanted compound is the fine metal sulfide particles, coated on the surface of the coarse substrate. The biotreatment of the sulfide mineral concentrate is biooxidized until the fine metal sulfide particles in the sulfide mineral concentrate are biooxidized in a desired amount to free the precious metals, (e) contacting the biooxidized fine metal sulfide particles with a noble metal leaching agent to dissolve the precious metals from the biooxidized fine metal sulfide particles, and (f) recovering the precious metals from the leach agent. 40. The method of claim 39, wherein the counter surface reactor is formed by stacking coarse substrates coated with a plurality of concentrates with heaps, (g) biooxidizing the desired amount of fine metal sulfide particles coated on the surface of the plurality of coarse substrates and then destroying the hips, and (h) further comprising separating the biooxidized fine metal sulfide particles from the plurality of coarse substrates before contacting with the leach agent. 41. The method of claim 40, further comprising repeating steps (a) through (f) using a plurality of coarse substrates separated from the biooxidized fine metal sulfide particles. 41. The method of claim 40, wherein separating the biooxidized fine metal sulfide particles from the plurality of coarse substrates comprises placing a coarse substrate coated with a plurality of concentrates on a screen and then spraying with water. 41. The method of claim 40, wherein separating the biooxidized fine metal sulfide particles from the plurality of coarse substrates comprises rolling a coarse substrate coated with a plurality of concentrates in a trommel. 40. The method of claim 39, wherein the non-surface surface reactor forms a coarse substrate coated with a plurality of concentrates in a tank, (g) separating the biooxidized fine metal sulfide particles from the plurality of coarse substrates before contacting with the leach agent. 45. The method of claim 44, further comprising repeating steps (a) through (f) using a plurality of coarse substrates separated from the biooxidized fine metal sulfide particles. 45. The method of claim 44, wherein the method of separating the biooxidized fine metal sulfide particles from the plurality of coarse substrates comprises filling the tank with an aqueous solution and then rapidly draining the tank to transport the biooxidized fine metal sulfide particles out of the tank with the aqueous solution. How to be. 40. The method of claim 39, wherein the plurality of coarse substrates comprise coarse refractory sulfide ore particles having precious metals occluded within the metal sulfide particles. The method of claim 47, (g) separating the biooxidized fine metal sulfide particles from the plurality of coarse substrates before contacting with the leach agent, (h) grinding the plurality of coarse substrates to a particle size sufficient to separate the fine metal sulfide particles from the plurality of coarse substrates, (i) preparing a second sulfide mineral concentrate consisting of fine metal sulfide particles obtained from a plurality of milled coarse substrates, (j) coating a plurality of second coarse substrates with a second concentrate, (k) forming a second non-surface surface reactor by stacking a plurality of second coated coarse substrates in a heap or placing a plurality of second coated coarse substrates in a tank, (l) biooxidizing a second concentrate of fine metal sulfide particles, (m) contacting the second biooxidized concentrate with a noble metal leaching agent to dissolve the precious metals from the second biooxidized concentrate, (n) recovering the precious metals dissolved from the second concentrate from the leaching agent. 48. The method of claim 47, wherein the coarse refractory sulfide ore particles are derived from a noble metal containing refractory sulfide ore used to prepare the concentrate. 48. The method of claim 47, wherein the coarse refractory sulfide ore particles also contain mineral carbonate. 47. The method of any one of claims 39-46, wherein the material used in the plurality of coarse substrates is at least one material selected from the group consisting of volcanic rock, gravel and mineral carbonate containing rock. 51. The method of any one of claims 39-50, wherein the nominal particle size of the plurality of coarse substrates is from about 0.6 cm to about 2.5 cm. 51. The method of any one of claims 39-50, wherein the amount of coated concentrate on the plurality of coarse substrates is from about 10% to about 30% by weight. 51. The method of any one of claims 39-50, wherein the sulfide mineral concentrate comprises at least about 20% by weight metal sulfide particles. 51. The method of any one of claims 39-50, wherein the sulfide mineral concentrate comprises at least about 40 weight percent metal sulfide particles. 51. The method of any one of claims 39-50, wherein the sulfide mineral concentrate comprises at least about 70% by weight of metal sulfide particles. 51. The method of any one of claims 39-50, wherein the sulfide mineral concentrate comprises 40-80% by weight of metal sulfide particles. 51. The method of any one of claims 39-50, wherein the concentrate has a particle size of greater than about 25 μm. The method of any one of claims 39-50, wherein the particle size of the concentrate is less than about 106 μm. 51. The method of any one of claims 39-50, wherein the nominal particle size of the concentrate is less than about 75 μm. 51. The method of any one of claims 39-50, wherein the recovered precious metal is one or more selected from the group consisting of gold, silver and platinum. 51. The method of any one of claims 39-50, wherein the leach agent is selected from the group consisting of thiourea and cyanide. The method of claim 1 wherein the solid material is a sulfide mineral concentrate comprising fine metal sulfide particles containing the desired useful metals and the unwanted compound is the fine metal sulfide particles and coated on the surface of the coarse substrate. Biotreatment of the sulfide mineral concentrate is to biooxidize the fine metal sulfide particles to produce a bioleaching drainage solution and to dissolve the metal portion of the metal sulfide particles, (e) recovering the desired useful metals from the bioleaching effluent solution. 64. The method of claim 63, wherein the concentrate of fine metal sulfide particles consists of particles of a copper sulfide mineral and the metal recovered is copper. 65. The method of claim 64, wherein the method of recovering copper from the bioleaching effluent solution comprises one or more methods selected from the group consisting of solvent extraction, copper cementation, and electrowinning. 64. The method of claim 63, wherein the concentrate of fine metal sulfide particles consists of a zinc sulfide mineral and the metal recovered is zinc. 64. The method of claim 63, wherein the concentrate of fine metal sulfide particles consists of a nickel sulfide mineral and the metal recovered is nickel. (a) distributing a concentrate of refractory sulfide mineral on top of the bottom of the coarse support material selected from the group consisting of volcanic rock, gravel, carbonate mineral containing waste rock, brick, concrete block and slag, (b) biooxidizing a concentrate of the refractory sulfide mineral, (c) leaching precious metals from biooxidized refractory sulfide minerals using leaching agents, (d) recovering precious metals from the leaching agent A method for recovering noble metals from a concentrate consisting of noble metal-containing fine refractory sulfide mineral particles comprising a. 69. The method of claim 68, wherein the precious metal recovered from the leach agent is at least one selected from the group consisting of gold, silver and platinum. 69. The method of claim 68, wherein the precious metal recovered from the leach agent is gold. 69. The method of claim 68, wherein the coarse support material is selected from the group consisting of volcanic rock, gravel, and carbonate mineral containing rock. 69. The method of claim 68, wherein the support material is volcanic rock. 73. The method of any of claims 68 to 72, wherein the leach agent is selected from the group consisting of thiourea and cyanide. 73. The method of any of claims 68 to 72, wherein the leach agent is thiourea. 73. The method of any of claims 68 to 72, further comprising intermittently adding fresh concentrate to the top of the hips. 76. The method of claim 75, wherein the noble metals are intermittently leached from refractory sulfide minerals that are biooxidized using thiourea. 73. The method of any one of claims 68-72, wherein the particle size of the coarse support material is greater than about 0.6 cm. The method of any of claims 68-72, wherein the particle size of the concentrate is less than about 150 μm. (a) preparing a sulfide mineral concentrate consisting of fine metal sulfide particles obtained from sulfide ores, (b) distributing the concentrate to the top of the bottom of the coarse support material selected from the group consisting of volcanic rock, gravel, carbonate mineral containing rock, brick, concrete blocks and slag, (c) biooxidizing the concentrate, (d) recovering the useful metals from the sulfide ore, comprising recovering the useful metals from the solution used to biooxidize the metal sulfide mineral. 80. The method of claim 79, wherein the recovered useful metals are selected from the group consisting of copper, zinc, nickel and uranium. 80. The method of claim 79, wherein the recovered metal is copper. 80. The method of claim 79, wherein the coarse support material is selected from the group consisting of volcanic rock, gravel, and carbonate mineral containing rock. 80. The method of claim 79, wherein the support material is volcanic rock. 84. The method of any one of claims 79-83, further comprising intermittently adding fresh concentrate to the top of the heap. 84. The method of any one of claims 79-83, wherein the particle size of the coarse support material is greater than about 0.6 cm. 84. The method of any one of claims 79-83, wherein the particle size of the concentrate is less than about 150 μm.

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