CN108130428B

CN108130428B - Method for extracting gold and silver from ore

Info

Publication number: CN108130428B
Application number: CN201711414776.8A
Authority: CN
Inventors: 陈运法; 肖力; 王永良; 钱鹏; 叶树峰
Original assignee: Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS
Priority date: 2017-12-22
Filing date: 2017-12-22
Publication date: 2021-03-05
Anticipated expiration: 2037-12-22
Also published as: CN108130428A

Abstract

A method for extracting gold and silver from ores comprises the following steps: (1) ball-milling the materials until 90% of the materials pass through a 400-mesh sieve, and fully realizing the dissociation and exposure of the gold and silver monomers; (2) adding hydrogen peroxide to adjust the oxidation-reduction potential of the ore pulp and eliminate the influence of reducing substances in the ore pulp; (3) adding limestone to adjust the pH value of the ore pulp to make the ore pulp neutral or weakly alkaline; (4) a novel thiosulfate-potassium ferricyanide leaching system is adopted to leach out the ore pulp. The method has the advantages of low reagent consumption, replacement of the traditional copper ammonia complex oxidant by using potassium ferricyanide as the oxidant, no need of adding ammonia water, reaction under neutral and normal temperature environment, and higher leaching rate than that of the traditional cyanidation method.

Description

Method for extracting gold and silver from ore

Technical Field

The invention belongs to the technical field of hydrometallurgy, and particularly relates to a method for extracting gold and silver from ores.

Background

The cyanidation method is a common method for extracting gold at present, gold and silver are leached from ores by cyanide solution in 1887, the history of more than 100 years is existed so far, the cyanidation method gold extraction process is mature, and the technical and economic indexes are ideal. Statistics show that gold extracted by the stirred cyanidation method accounts for about 64% of the total yield in the world. However, the cyanidation process uses highly toxic sodium cyanide as the leaching agent and thus the use of this process involves a significant environmental risk. Cyanide tailings are formed after the gold and silver-containing materials are leached by a cyanidation method, and data show that the cyanide tailings generated by gold and silver extraction by the cyanidation method reach 2450 million tons every year, and the tailings contain CN & lt- & gt and can cause serious pollution if the heavy metal ions are transferred to the environment. With the further deepening of the knowledge of the cyanidation process, the limitation of the cyanidation process is increasingly shown. The main body is as follows: (1) leaching kinetics of gold and silver extracted from ores by a stirred cyanidation method is slow, and the leaching time is generally 48 hours or longer; (2) is easily interfered by copper, lead, zinc and other elements, and consumes a large amount of CN < - > when the ore contains the elements, thereby reducing the economic benefit of the method. (3) The leaching effect of the treatment of ores which are difficult to treat, such as carbon-containing ores, is poor, and the leaching rate is low. In conclusion, the search for an efficient, economical and environmentally friendly alternative to cyanidation is driven not only by environmental considerations but also by economic factors.

At present, researchers at home and abroad develop various non-cyanide methods, including a thiourea method, a thiosulfate method of a cuprammonium system, a halogen method (including a chlorination method, a bromination method and an iodination method), a polysulfide method and a thiocyanate method. These non-cyanide processes, while environmentally superior to cyanide processes, suffer from a number of disadvantages: (1) the consumption of the medicament is large, the gold extraction cost is higher than that of a cyaniding method, for example, the medicament consumed by a thiourea method is usually several kilograms or even dozens of kilograms, which seriously restricts the popularization of non-cyanide medicaments; (2) the medicament is unstable, such as thiourea, thiosulfate and the like which belong to metastable substances and are easily oxidized by an oxidant; (3) the process conditions are complex and difficult to industrialize, for example, a chlorination method usually generates chlorine gas which reacts with other reducing substances in ores to make the system difficult to control, and a thiosulfate method of a cuprammonium system usually requires the pH of a solution to be between 10 and 12 and is difficult to control; (3) the poor selectivity can cause the dissolution of other metals and influence the reduction and recovery of gold and silver ions.

At present, the thiosulfate process is considered to be a non-cyanide process that is the most likely alternative to the cyanidation process. Although related researchers have made certain progress in the extraction of gold and silver from ores in cuprammonium thiosulfate systems, the development of the method still meets certain bottleneck. The expression is as follows: (1) the using amount of thiosulfate is large and is generally between 0.1 and 0.5M, meanwhile, the consumption of thiosulfate is large, the consumption of the medicament greatly increases the cost of gold and silver extraction by the method, and the popularization of the method is greatly restricted; (2) in the leaching process of the system, a copper-ammonia complex is used as an oxidant, a large amount of ammonia water is inevitably added to stabilize copper ions, and the cost in the aspect of environmental protection is increased due to the large amount of ammonia water; (3) the thiosulfate solution and the copper ammonia complex ions in the system are subjected to oxidation-reduction reaction, so that a great amount of loss of a leaching agent is caused, and the polythionate pair generated by the reaction can influence the subsequent reduction of gold and silver. In view of the above, in order to further develop the thiosulfate method, it is necessary to reduce the amount of thiosulfate used and to use a stable and mild oxidizing agent.

Disclosure of Invention

In view of the shortcomings of the prior art, the present invention aims to provide a method for extracting gold and silver from ores so as to solve at least one of the above technical problems.

The invention is realized by the following technical scheme:

the invention provides a method for extracting gold and silver from ores, which comprises the following steps

(1) Ball-milling the ore until the granularity is 90%, and sieving the ore with a 400-mesh sieve to obtain ore pulp;

(2) adding hydrogen peroxide into the ore pulp obtained in the step (1) to fully oxidize the reducing substances in the ore pulp.

(3) Adding water to adjust the concentration of the ore pulp to 20-50%, and then adding an alkaline substance to adjust the pH of the ore pulp to be neutral or alkalescent;

(4) and (3) respectively adding a thiosulfate solution and a potassium ferricyanide solution into the ore pulp obtained in the step (3) to ensure that the concentration of thiosulfate is 0.01-0.05M and the concentration of potassium ferricyanide is 10-50 mM, carrying out leaching reaction at the temperature lower than 30 ℃, and after leaching is finished, carrying out solid-liquid separation to obtain a gold-silver-containing filtrate.

Preferably, in the step (1), the ball milling is wet milling, and the concentration of the ore pulp is 30-50%.

Preferably, in the step (2), the addition amount of the hydrogen peroxide is 1.1-1.2 times of the theoretical value.

Preferably, in the step (3), the alkaline substance comprises lime water, sodium hydroxide, potassium hydroxide and quicklime.

Preferably, in the step (3), mechanical stirring is used during the size mixing process.

Preferably, in the step (4), mechanical stirring is adopted in the leaching process.

Preferably, in the step (4), the oxidation-reduction potential of the ore pulp in the leaching process is not lower than 100mv, wherein 100mv is the potential relative to a standard Ag/AgCl electrode.

According to the technical scheme, the method for extracting gold and silver from the ore has the following beneficial effects:

(1) the invention has low reagent consumption, adopts potassium ferricyanide as an oxidant to replace a copper ammonia complex oxidant, and does not need to add ammonia water;

(2) the reaction of the invention is carried out in a neutral and normal temperature environment;

(3) the invention effectively eliminates the interference of reducing impurities in the ore pulp by adding hydrogen peroxide;

(4) the leaching rate of the invention is higher than that of the traditional cyanidation method.

Drawings

Fig. 1 is a flow chart of extracting gold and silver from ores in the embodiment of the invention.

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

The invention discloses a method for extracting gold and silver from ores. The method comprises the following steps: (1) ball-milling the materials until 90% of the materials pass through a 400-mesh sieve, and fully realizing the dissociation and exposure of the gold and silver monomers; (2) adding hydrogen peroxide to adjust the oxidation-reduction potential of the ore pulp and eliminate the influence of reducing substances in the ore pulp; (3) adding limestone to adjust the pH value of the ore pulp to make the ore pulp neutral or weakly alkaline; (4) a novel thiosulfate-potassium ferricyanide leaching system is adopted to leach out the ore pulp. The method has the advantages of low reagent consumption, replacement of the traditional copper ammonia complex oxidant by using potassium ferricyanide as the oxidant, no need of adding ammonia water, reaction under neutral and normal temperature environment, and higher leaching rate than that of the traditional cyanidation method.

Specifically, the invention provides a method for extracting gold and silver from ores, and fig. 1 is a flow chart of extracting gold and silver from ores in the embodiment of the invention. As shown in FIG. 1, the steps are as follows

(1) Grinding: putting the gold-containing material into a ball mill, wherein the liquid-solid ratio is 1: 1, the ball milling time is determined according to ores, and the granularity of ore pulp after ball milling reaches 90 percent and then the ore pulp passes through a 400-mesh sieve. Grinding ore is beneficial to improving the monomer dissociation degree of gold and silver, opening the package of gold and silver and is beneficial to the contact reaction of the medicament and the gold and silver. Meanwhile, the ore grinding can partially oxidize sulphide ore, organic carbon and other reducing substances in the ore, and the influence on leaching of gold and silver is reduced.

(2) Adjusting oxidation reduction potential: after the ore pulp is adjusted to be neutral by adding limestone, the oxidation-reduction potential of the ore pulp still needs to be further adjusted, because the leaching system of the invention contains an oxidizing compound potassium ferricyanide, if the content of reducing substances (mainly some sulfide ores) in the ore pulp is too high, a large amount of potassium ferricyanide in the leaching system is consumed, and the leaching effect is not ideal. Therefore, according to the sulfide content in the ore, about 1.2 times of theoretical value of hydrogen peroxide is added to fully oxidize reducing substances such as sulfide ore in the ore pulp, and the leaching and stirring are carried out for about 2 hours.

(3) Size mixing: adding lime water or caustic soda flakes to adjust the pH of the pulp to be neutral or alkalescent. And opening the stirring device, setting the mechanical stirring speed to be 250rmp, and stirring for 2 hours to ensure that the acidic substances in the ore pulp fully react with the alkaline substances. Stopping stirring after 2h, measuring the pH value of the ore pulp by using pH test paper, if the ore pulp is acidic, continuously adding lime water to adjust to be neutral, and continuously starting mechanical stirring until the acid-base value of the ore pulp is stabilized to be neutral or alkalescent.

(4) Stirring and leaching: adding the prepared thiosulfate solution and the potassium ferricyanide solution into the ore pulp respectively, wherein the concentration of thiosulfate is 0.01-0.0 SM, and the concentration of potassium ferricyanide is 10-50 mM. The leaching temperature is lower than 30 ℃, and the decomposition of thiosulfate is accelerated due to the overhigh temperature. The mechanical stirring speed is set to be 250rmp, the oxidation-reduction potential of the ore pulp is detected regularly during the leaching and stirring period, and the oxidation-reduction potential of the ore pulp is ensured to be not lower than 100mv (relative to a standard Ag/AgCl electrode), and the agitation leaching is carried out for about 24 hours. And after leaching, carrying out solid-liquid separation to obtain gold-silver-containing filtrate.

The method for extracting gold and silver from ore provided by the invention is further described in detail below with reference to specific examples and accompanying drawings.

Examples

The chemical components of the anode mud are as follows:

TABLE 1 silver residue element content (%, Au, Ag unit g/t) in some place

(1) Grinding: adding 500g of silver separating slag into a ball mill, adding 500ml of water, grinding for half an hour to ensure that the granularity of the silver separating slag reaches 90 percent and the silver is sieved by a 400-mesh sieve, and fully dissociating the gold and the silver by a monomer.

(2) Adjusting oxidation reduction potential: and (3) standing the ore pulp subjected to ball milling, fully precipitating the ore pulp after a period of time, pouring off redundant washing water, and adjusting the volume of the ore pulp to 1000ml and the concentration of the ore pulp to 33%. Adding 10ml of hydrogen peroxide with the mass fraction of 30%, mechanically stirring for 2 hours, adjusting the rotating speed of a stirring paddle to 1500r/min, and fully oxidizing the reducing substances in the ore pulp.

(3) Size mixing: the pulp after the redox potential adjustment is acidic, 12.8g of sodium hydroxide is weighed and added into the pulp, and the pulp is adjusted to be neutral or weakly alkaline. And mechanically stirring for 30min to obtain the ore pulp with stability of 7-8.

(4) Stirring and leaching: the leaching conditions are 0.05M sodium thiosulfate pentahydrate, 1mM potassium ferricyanide and 1mM sodium ferrocyanide decahydrate, the liquid-solid ratio is 2: 1, the leaching is carried out at normal temperature and normal pressure, and the leaching time is 24 hours. 6h before leaching, supplementing potassium ferricyanide solution every 1h, adding 5ml of 0.2M potassium ferricyanide solution, and maintaining the oxidation-reduction potential of the ore pulp at 100mV (relative to Ag/AgCl reference electrode). And after leaching for 24 hours, taking a small amount of sample, filtering by using a circulating water pump, collecting filtrate, and measuring the concentration of the gold-silver complex in the filtrate. The leaching rate of gold is 88.83 percent, and the leaching rate of silver is 60.04 percent.

In conclusion, the consumption of the reagent is low, the potassium ferricyanide is used as the oxidant to replace the traditional copper ammonia complex oxidant, ammonia water is not needed to be added, the reaction is carried out in a neutral and normal-temperature environment, and the leaching rate is higher than that of the traditional cyaniding method.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting gold and silver from ores is characterized by comprising the following steps:

(2) adding hydrogen peroxide into the ore pulp obtained in the step (1) to fully oxidize reducing substances in the ore pulp;

(4) adding thiosulfate solution, potassium ferricyanide solution and sodium ferrocyanide solution into the ore pulp obtained in the step (3) respectively for agitation leaching under the conditions that the concentration of sodium thiosulfate pentahydrate is 0.05M, the concentration of potassium ferricyanide is 1mM, the concentration of sodium ferrocyanide decahydrate is 1mM, and the liquid-solid ratio is 2: 1, leaching at normal temperature and normal pressure of lower than 30 ℃, wherein the leaching time is 24 hours; supplementing potassium ferricyanide solution every 1h 6h before leaching, adding 5mL of 0.2M potassium ferricyanide solution, maintaining the redox potential of the ore pulp at 100mV relative to a standard Ag/AgCl reference electrode, and after leaching, performing solid-liquid separation to obtain gold-silver-containing filtrate.

2. The method for extracting gold and silver from ores according to claim 1, wherein in the step (1), the ball milling is wet milling, and the concentration of ore pulp is 30-50%.

3. The method for extracting gold and silver from ores according to claim 1, wherein in the step (2), the addition amount of hydrogen peroxide is 1.1-1.2 times of a theoretical value.

4. The method for extracting gold and silver from ore according to claim 1, wherein in the step (3), the alkaline substances comprise lime water, sodium hydroxide, potassium hydroxide and quicklime.

5. The method for extracting gold and silver from ores according to claim 1, wherein mechanical stirring is used in the slurry mixing process in the step (3).

6. The method for extracting gold and silver from ore according to claim 1, wherein in the step (4), the leaching process adopts mechanical stirring.