MXPA97003969A

MXPA97003969A - Method for the treatment of mineral material which has organic carbon to facilitate larecuperation of a metal preci

Info

Publication number: MXPA97003969A
Application number: MXPA/A/1997/003969A
Authority: MX
Inventors: L Simmons Gary
Original assignee: Santa Fe Pacific Gold Corporation
Priority date: 1994-11-29
Filing date: 1995-11-14
Publication date: 1998-01-01

Abstract

The present invention relates to a method for processing a mineral material, which has a precious metal to reduce the potential for problems with the recovery of the precious metal when present organic carbon, the method comprising the steps of: a) providing a sludge feed having particulate mineral material made of sludge with an aqueous liquid, wherein i) said mineral material comprises a precious metal selected from the group consisting of gold, silver and combinations thereof, and organic carbon, which has the ability to interfering with the recovery of the precious metal, said mineral material also comprises a sulfur sulfide in association with said precious metal and from which the precious metal is difficult to separate, and ii) at least 80% by weight of the precious metal particles. said mineral material in the feeding mud are smaller than 38 microns in size, which facilitate the oxidizing treatment of the mater mineral to reduce the ability of said organic carbon to interfere with the recovery of the precious metal, and b) oxidatively treating said mineral material in the feed slurry which comprises subjecting the feed sludge to an oxidation environment at a higher temperature than about 190 ° C to produce an oxidized sludge, wherein the ability of said organic carbon to interfere with the recovery of said precious metal from the oxidized sludge is reduced, where, during the oxidative treatment of said sludge, at least 96% of the sulfur sulfur in the feed slurry is oxidized, thus allowing substantial passivation of the organic carbon to reduce the ability of said organic carbon to interfere with the recovery of said metal.

Description

METHOD FOR THE TREATMENT OF MINERAL MATERIAL WHICH HAS ORGANIC CARBON TO FACILITATE THE RECOVERY OF A PRECIOUS METAL FIELD OF THE INVENTION The present invention involves the oxidation under pressure of a mineral material containing a precious metal, such as gold bearing ores, which are refractory for gold recovery operations due to the presence of organic carbon, and also, sulfide minerals.

BACKGROUND OF THE INVENTION It is known that several ores that carry precious metal, such as many ores that carry gold and silver, are refractory to normal recovery techniques, such as cyanidation. A mineral can be refractory due to the presence of sulfur minerals, with which the precious metal is associated and from which the precious metal is difficult to separate. Typically, refractory sulfur ores are treated by decomposing the sulfide minerals in order to release the precise metal for subsequent recovery. A method for the treatment of refractory sulfide ores is to oxidize under pressure the ore at elevated temperature and pressure under acidic conditions to oxidize the sulfur sulfur in the sulfide minerals. Another reason that a ore can be refractory is that the ore contains significant amounts of organic carbon that can absorb the precious metal in competition with a recovery operation. For example, during the recovery of cyanide, a mine is leached with a cyanide to form a complex of cyanide with the precious metal in the ore. The precious metal-cyanide complex can be absorbed onto the activated carbon glands and the precious metal recovered from the activated carbon granules. When organic carbon is present in the ore, however, organic carbon can compete with the activated carbon to absorb the precious metal-cyanide complex, thus significantly reducing the amount of precious metal that is recovered. The absorption of the precious metal through the activated carbon is usually referred to as pregnant denillation (preg-despilaramiento), since the organic carbon is removed from the precious metal from a pregnant solution. The process of oxidation under acid pressure that has been used for refractory sulfur ores has not been found to be satisfactory to sufficiently reduce the problem of pre-de-profiling when organic carbon is present. A procedure that has been used to treat refractory ores of organic carbon is to subject the ore to a chlorination treatment before recovering the gold using a material containing chlorine. However, chlorination can be very expensive and not satisfactory when the ore is also refractory due to the presence of sulfide minerals that are associated with gold. A method that has been used for the treatment of ores that are refractory due to the presence of both sulfur minerals and organic carbon, is to oxidatively calcify the ore to substantially oxidize all of both the organic carbon and the sulfide minerals. However, the rating is expensive, because the ore must be ground dry. Also, when the ore contains arsenic, a significant amount of arsenic is volatilized during calcination and has a significant environmental problem. A similar problem also occurs for mercury, when mercury is present in the ore. Also, the solid or calcined residues from the calcination process usually contain significant amounts of toxic substances, such as arsenic, in a soluble form, which require substantial additional treatment for safe disposal. There is a need for relatively simple and inexpensive methods for the treatment of gold bearing ores, which are refractory due to the presence of organic carbon, and especially for those ores that are also refractory due to the presence of sulfide minerals associated with the ores. gold.

COMPENDIUM OF THE INVENTION The present invention provides a method for treating ores containing precious metal and other mineral materials that are refractory due to the presence of organic carbon to reduce the ability of pregnant pregnant organic waste and, thus, to obtain high recoveries of the precious metal . The procedure is particularly useful for treating complete ore bearing gold, to allow for the subsequent recovery of gold. With the method of the present invention, it has surprisingly been found that oxidation under pressure can be used to effectively treat organic carbon refractory mineral materials, when the mineral material is ground to a very fine size and subjected to severe oxidation conditions. under pressure. At least 80% by weight of the mineral material particles in a feed slurry are smaller than about 40 microns in size, which facilitates oxidation under pressure to reduce the ability of organic carbon to interfere with the possible recovery of the Precious metal of the ore. In addition to the very fine particle size of the mineral material, the oxidation under pressure is conducted at a high temperature, greater than about 190 ° C. In a preferred embodiment, the mineral material is milled to a size wherein at least about 80% by weight of the particles of the mineral material are smaller than about 30 microns, and most preferably smaller than about 20 microns. A preferred oxidation treatment temperature under pressure is greater than about 200 ° C. Particularly good results are obtained at treatment temperatures greater than about 210 ° C, and especially when the treatment temperature is greater than about 220 ° C. A particularly surprising benefit when using the process of the present invention is that high recoveries of precious metal can be obtained for mineral materials containing significant organic carbon using an oxidation treatment under pressure prior to the recovery of the precious metal, without oxidizing substantially all organic carbon. Therefore, it is believed that the organic carbon that remains un-oxidized after oxidation under pressure has been passivated during oxidation under pressure to reduce the activity of the activated carbon as an adsorbent for the precious metal. In addition to organic carbon, the mineral material can also be refractory due to the presence of sulfide minerals with which the precious metal is associated and from which the precious material is difficult to separate. During oxidation, substantially all of the sulfur is oxidized, thus liberating the precious metal from the sulfide minerals and allowing the precious metal to be recovered, such as through cyanuration. However, it has been found that at least 96% of the sulfur sulfide must be oxidized in order to effectively treat the organic carbon to significantly reduce the ability of the organic carbon to the pregnant waste of the precious metal during the subsequent recovery operations. precious metal. Therefore, improved recoveries of the precious metal, which can be achieved according to the process of the present invention, are due to the treatment of the organic carbon and in addition to the treatment that is necessary to substantially release all the precious metal from the sulfide minerals. . After oxidation under pressure, the oxidized sludge should have a very low pH, preferably a pH below 1.5, to ensure a satisfactory treatment of the organic carbon. When the mineral material has sufficient sulfur sulfur to produce a desired level of acid for oxidation under pressure, then pretreatment with sulfuric acid before oxidation under pressure is not necessary. If a mineral material, such as a carbonate containing ore, is treated, which contains enough sulfur sulfur to produce the required acid, then the mineral material can be mixed with another mineral material, which has sufficient sulfur sulfur to generate the desired acid, including compensation for the acid that can be consumed by carbonate materials.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 in a procedural flow chart for one embodiment of the present invention. Figure 2 is a graphic representation of the percentage of gold extraction versus the milled size for some ore types from the Twin Creeks Mine. Figure 3 is a graphic representation of gold extraction versus ground size for other types of ore from the Twin Creeks Mine. Figure 4 is a graphical representation of the oxidation of sulfur sulfur, oxidation of organic carbon and extraction of gold against the milled size for a composite sample of gold from the Twin Creeks Mine. Figure 5 is a graphical representation of the oxidation of sulfur sulfur, organic carbon and gold extraction against temperature for a composite sample of gold from the Twin Creeks Mine. Figure 6 is a graphical representation of sulfur sulfide oxidation, organic carbon oxidation, and gold extraction against free acid in an oxidized sludge for a gold composite material from the Twin Creeks Mine. Figure 7 is a bar graph showing the ability of pregnant ejaculation of a sample of ore from the Mine and Twin Creeks, as it progresses through oxidation under pressure. Figure 8 is a bar graph showing the ability of pregnant denillation of another ore sample from the Twin Creeks Mine as it progresses through oxidation under pressure.

DETAILED DESCRIPTION The present invention provides a method for processing a mineral material containing a precious metal, which is refractory due to the presence of organic carbon, which can compete for absorption of the precious metal and can thus reduce the recovery of the precious metal during the recovery operations of the precious metal. The very fine particles of the mineral material containing the precious metal are oxidized under pressure, under severe conditions of oxidation under pressure. It has been found that both a very fine particle size and a high oxidation temperature under pressure are necessary to satisfactorily treat the mineral material to facilitate high recovery of the precious metal. As used herein, "precious metal" refers to gold and / or silver. The process of the present invention is especially preferred for use with gold-bearing mineral materials. As used herein, the mineral material includes complete ores, ore concentrates, waste, and waste from previous mining or milling operations. The present invention is particularly useful for the treatment of complete ores, because the ability of pregnant pregnant women to be able to loosen whole ores can be satisfactorily reduced without the expense of preparing an ore concentrate. Furthermore, it has been found that to prepare an ore concentrate through flotation of a complete ore having a significant amount of organic carbon, it is very difficult to prevent the organic carbon from concentrating in the ore concentrate. In addition, when preparing an ore concentrate, there is at least some loss of the precious metal to rejection of preparing the ore concentrate. The problems associated with the ore concentrates, however, can be avoided by treating a complete ore according to the process of the present invention. The organic carbon, which can be treated in accordance with the present invention includes any organic carbonaceous material, which has an affinity for the precious metal, a salt of the precious metal, and / or a complex of the precious metal with a ligand, of so that the organic carbon is active as an adsorbent that can pregnantly release the precious metal during the recovery operations of the precious metal. For example, during the recovery of the precious metal, through cyanidation, organic carbon can act as an adsorbent for a gold-cyanide complex and can, therefore, compete for gold with the recovery procedure, thus reducing gold recovery. The mineral materials that can be treated with the present invention can comprise, in addition to the organic carbon, sulfide minerals with which the precious metal can be closely associated and from which the precious metal can be difficult to separate. It has been found with the process of the present invention that oxidation under pressure can be successfully used to discharge, or release, the precious metal from the sulfide minerals and also to oxidize and / or passivate the organic carbon, so that the activity Organic carbon, as an adsorbent, is reduced to a level that allows high recoveries of precious metal. However, it has been found that substantially all of the sulfur sulfur present in the mineral material must be oxidized before a significant benefit is obtained from the treatment of the organic carbon. Surprisingly, at least 96% of the sulfur sulfide must be oxidized before the significant benefit of organic carbon treatment is realized. Therefore, according to the present invention, severe oxidation treatment conditions under pressure are required. The surprising discoveries leading to the process of the present invention were made during the search in relation to possible processes for the treatment of refractory ore bearing gold from the Twin Creeks Mine in Nevada, which belongs to Sante Fe Pacific Gold Corporation. The Twin Creeks Mine contains several different types of ores with variable mineralogies. Some of the types of ores comprise very high levels of organic carbon, sometimes in an excess of 1% by weight, which will preferentially disperse all available gold during normal recovery procedures by cyanidation. All types of ores with a high organic carbon content are also refractory due to the presence of sulfide minerals with which gold is associated. Tests were carried out on refractory ores from the Twin Creeks Mine to identify the possible treatments that can allow a satisfactory gold recovery. Refractory ores contain significant amounts of both organic carbon and sulfur minerals. Initial treatment attempts included oxidation under pressure of a complete ore under unusually severe conditions of operation. The ore was ground to a size where 80% of the particles are 74 microns or smaller in size (P80 = 74 microns). The ore is then oxidized under pressure, under highly acidic conditions at a temperature of 225 ° C and at a pressure of 3172 kPa, with an oxygen gas overpressure of 690 kPa over a period of two hours in a batch autoclave. Essentially all sulfur sulfur oxidized (97% +), thus ensuring that essentially all the gold was released from the sulfide minerals. Gold recoveries, using a cyanidation treatment after oxidation under pressure, remained very slow, however, indicating that the oxidation treatment under pressure did not satisfactorily reduce the ability to pregnant organic carbon. After the initial failure with oxidation under pressure, a variety of other procedures were treated. Chlorination was treated, but proved ineffective in oxidizing sulfur sulfur. Significant improvements were experienced in gold recoveries, using an oxidizing calcination technique, which proved effective to substantially oxidize all sulfur sulfur and organic carbon. Recoveries of gold through cyanidation after oxidative calcination were between about 80% and 90%. Although it provides significant improvements in gold recoveries, however, the calcination had severe problems. First, arsenic and mercury in the ore volatilized during the drying and milling of the ore. Also, the calcination residues contained sficant amounts of soluble arsenic, which is inadequate for waste removal without sficant additional treatment. In addition to these sficant environmental problems, the moisture content of the ore was too high for the drying and milling, at low cost, of the ore. Moreover, fine dry milling (P80 = 74) was required to obtain acceptable gold recoveries. In addition, dry-ground ores proved to be very difficult to feed on a continuous basis. Also, it was determined that the calcination could have been conducted at low temperatures, which could represent sficant engineering, desand safety problems. Due to the problems associated with oxidizing calcination, additional research was carried out in the oxidation treatment under pressure, mainly for its ability to produce stable arsenic residues. Although milling prior to P80 = 74 microns resulted in substantially complete sulfur sulfide oxidation and gold release, gold recoveries were, however, very low. Surprisingly, however, it was found that a combination of very fine grinding and severe oxidation conditions under pressure result in sficantly increased gold recoveries. The result is particularly surprising, since high recoveries of gold are obtained without substantially oxidizing all the organic carbon in the treated ores. Therefore, without being bound by theory but to aid understanding of the present invention, it is believed that the process of the present invention results in sficant passivation of the organic carbon that remains without oxidation during the oxidation treatment. This result is particularly important since all the tests indicate that, even after the most severe conditions of oxidation treatment under pressure, a substantial amount of the organic carbon remains without oxidizing. Therefore, unlike oxidizing calcination, the present invention does not require complete oxidation of organic carbon. As used herein, the oxidation of organic carbon refers to chemically combining carbon with oxygen. Much of the oxidized organic carbon can be in the form of carbon dioxide. According to the process of the present invention, the mineral material is minced to a size of P80 = 40 microns or smaller, and preferably to a size of P80 = 30 microns or smaller. Although added to the cost due to additional milling, it has been found that especially high recoveries can be obtained with a particle size of mineral material of P80 = 20 microns or smaller. Particularly preferred for particular application is a particle size of from about P80 = 15 microns to about P80 = 25 ppm. The particulate mineral material of the appropriate size is slurried in an aqueous liquid and then subjected to an oxidizing treatment in an autoclave to leach, under pressure, the mineral material. As previously noted, in addition to the extremely fine particle size of the mineral material, the operating conditions of the oxidant treatment are severe. The temperature of the treatment should be greater than about 190 ° C, preferably greater than about 200 ° C and most preferably greater than about 210 ° C. Particularly good results are obtained with a treatment temperature greater than about 220 ° C. Depending on the particular ore, an especially preferred scale of treatment temperatures is from about 205 ° C to about 260 ° C. Oxidizing treatment is carried out in the pressure of an oxygen-containing material, which will typically be oxygen gas. The use of a pure oxygen gas is preferred to air. Typically, an oxygen gas overpressure greater than about 172 kPa is sufficient, although an oxygen gas overpressure greater than about 345 kPa is preferred. The total pressure of the treatment will generally be equal to the pressure exerted by the aqueous liquid at the treatment pressure plus the overpressure of the oxygen gas. The oxidizing treatment should generally be conducted with a retention time of about 120 minutes, with preferred times between about 30 minutes and about 90 minutes. As mentioned previously, a particularly surprising result of using the method of the present invention, is that high recoveries of precious metal can be achieved without oxidizing all, or substantially all, of the organic carbon in the mineral material being treated. Typically, satisfactory recoveries of gold can be obtained with an oxidation of less than about 60% by weight of the organic carbon, and it is preferably necessary to oxidize only from about 10% by weight to about 40% by weight of the organic carbon. In many cases, it may be possible to obtain high recoveries of gold with only 20% by weight of organic carbon oxidation, or less. As noted, the remaining non-oxidized organic carbon is believed to be passivated, since its activity as an adsorbent that can pregnantly strip the precious metal during precious metal recovery operations is significantly reduced. Although the present invention can be used for ore concentrates and other mineral materials, as previously noted, the present invention is particularly useful for the treatment of complete ores. In this way, the problems associated with the treatment of ore concentrates are avoided. The present invention is useful for any ores containing organic carbon, but is particularly useful for those comprising more than about 0.3% by weight of organic carbon, preferably more than about 0.4% by weight of organic carbon, and most preferably more than about 0.6% by weight of activated carbon. Oxidizing treatment must be carried out under highly acidic conditions. Preferably, the liquid of an oxidized sludge produced during oxidation under pressure, should have a pH less than about a pH of 1.5. For ores containing a significant amount of sulfur sulfide, sufficient sulfuric acid can be produced during the oxidizing treatment step to provide the desired low pH. Otherwise, it may be necessary to add sulfuric acid to the feed sludge before the oxidizing treatment. When the mineral material comprises sulfide minerals, in addition to organic carbon, it has been found that, surprisingly, it is necessary to substantially oxidize all of the sulfur sulfur before obtaining a significant benefit from the organic carbon treatment. It has been found that at least about 96% of the sulfur sulfide must be oxidized to allow sufficient oxidation and / or passivation of the organic carbon. This is because the adsorptive activity of the organic carbon is not to be sufficiently reduced until after substantially all of the sulfur sulfide has been oxidized. The present invention can be used with any mineral material containing both sulfur sulfur and organic carbon. The mineral material may comprise more than about 2% by weight or even more than about 4% by weight of sulfur sulfide. In this way, the process of the present invention is particularly useful for refractory sulfur-complete ores, which also contain significant organic carbon. As previously mentioned, when enough sulfur sulfur is present to produce a desired level of sulfuric acid, it is not necessary to pre-treat the feeding sludge with sulfuric acid before the oxidizing treatment. Preferably, the liquid in the oxidized sludge after the oxidation treatment contains more than about 10 grams liter of free acid. Most preferably, the free acid will be greater than about 1.5 grams per liter. When the free acid, in the oxidized mud, is too low, it has been found that the recovery of the precious metal can be significantly reduced. When there is insufficient sulfur sulfur in the mineral material to generate sufficient sulfuric acid, then it may be necessary to pre-treat the feed slurry with sulfuric acid before the oxidizing treatment. A mineral material having a substantial amount of sulfur sulfide can be mixed with another mineral material, which is sulfur sulfur deficient, so that the mixture will have a sulfur sulfide sufficient to produce the required acid feed. Therefore, a ore having a high content of sulfur sulfide can be mixed with another ore having a high content of carbonate, which consumes the acid, to provide a mixture with a sufficiently high content of sulfur sulfur for balance the acid that can be consumed by the carbonate material and to provide the desired free acid in the oxidized mud. In one embodiment, it may be desirable to provide the sulfur sulfide in the form of an ore concentrate, from which the carbonate materials have been substantially removed for mixing purposes. In a preferred embodiment, when both the sulfur sulfur and the organic carbon are present in the mineral material, the treatment temperature is greater than about 190 ° C, the total pressure of the pretreatment is greater than about 1309 kPa, the overpressure of the oxygen gas is maintained at more than 172 kPa, and the liquid in the oxidized sludge is greater than about 10 grams per liter of sulfuric acid. Most preferably, the treatment temperature is greater than about 200 ° C, the total pressure of the treatment is greater than about 17.57 kg / cm 2 and the overpressure of the oxygen gas is maintained at about 172 kPa. Most preferably, the treatment temperature is greater than about 220 ° C, the total pressure is greater than about 2620 kPa, and the overpressure of the oxygen gas is maintained greater than about 345 kPa. After oxidation under pressure, the precious metal, in the oxidized mud, can be recovered through any suitable recovery technique. A recovery technique is to neutralize the oxidized sludge and then to contact the oxidized sludge with a cyanide, such as sodium cyanide, at a pH greater than about pH 10, so that the precious metal, in the oxidized sludge, can form a cyanide complex. The metal-cyanide complex can then be separated from the oxidized sludge by adsorbing the complex on carbon granules. The precious metal can then be recovered from the activated carbon and a purified metal product comprising the precious metal can be produced. A mode of the present invention will now be described with reference to Figure 1. A refractory whole ore feed 102 is provided having approximately 5.67 grams per ton of gold, which is previously associated with sulfide minerals. The ore 102 comprises between about 2% and 3% of the sulfur sulfur and from about 0.6 to about 1% by weight of organic carbon. The ore 102 is subjected to comminution 104, such as milling, to produce ore particles at a size of P80 = 20-22 microns. A feed slurry 106, which has crumbled ore particles, is formed into a slurry in an aqueous liquid, and is then subjected to oxidizing treatment 108 in the presence of oxygen gas 110. The oxidizing treatment is carried out in an autoclave at a temperature of about 225 ° C and at a total pressure of about 3172 kPa with an oxygen gas overpressure of 690 kPa, during a retention time of approximately 60 minutes. During oxidizing treatment 108, more than 96% of the sulfur sulfide in the feed slurry 106 is oxidized. Also, a portion, but less than all, the organic carbon is oxidized and the ability of pregnant pregnant organic carbon loosening without oxidation, is significantly reduced in relation to the ore in the feed sludge 106. An oxidized sludge 112 contains a solid residue of the ore 102 after the oxidizing treatment, and the liquid of the oxidized sludge has a pH of less than about 1.5. The oxidizing slurry 112 is subjected to neutralization 114, wherein the pH of the oxidized sludge 112 increases to more than about a pH of 10. A neutralized sludge 116 is then subjected to cyanidation 118 with carbon in pulp, through the sludge treatment neutralized 116 with sodium cyanide 120 to form a gold-cyanide complex, which can be adsorbed onto the activated carbon granules 122. The residues 124 of the carbon cyanidation in pulp are discarded through appropriate media and the granules activated carbon loaded with the gold 126 are separated and sent to gold recovery 128, wherein the gold-cyanide complex is divided from the charged activated carbon granules, and a purified gold 130 product is produced, as through electrodeposition and refining. The activated carbon granules 122, which are now devoid of the gold-cyanide complex, are recirculated to the carbon cyanide in pulp. The process of the present invention is further described in the following Examples, which are not limiting with respect to the scope of the process of the present invention.

EXAMPLE 1 This example shows the effect on the recovery of gold from a grinding size for various types of ore from the Twin Creek Mine. The compositional attributes of five individual types of ore (Ores MC, SWS, US, HGO, and DZ) and a material composed of ore (RC # 1) are shown in Table 1. The sulfur sulfur in the individual ores varies from a low of 1.12% by weight for the DZ ore to 8.34% by weight for the SWS ore. The organic carbon in the individual ores varies from a low of 0.36% by weight in the DZ ore to a high of 1.36% by weight in the MC ore. The RC # 1 composite comprises approximately 2.6 wt.% Sulfur sulfide and about 1.0 wt.% Organic carbon. A sample series was prepared having the different grind sizes for each of the ore types and for the ore composite. Each sample was made slurry with water and placed in an agitated tank batch autoclave. In the open autoclave, the sample in the form of sludge was treated with sulfuric acid to maintain a pH of 2. The autoclave is closed and the sludge is mixed and heated to the desired temperature for oxidation under pressure. Oxygen gas is introduced into the autoclave and the oxidation under pressure is conducted for a time of 90-120 minutes. The autoclave is then cooled rapidly with a sprinkling of water and the oxidized sludge is neutralized in two stages at a pH of 10.15 using lime. The sludge was then subjected to carbon cyanidation in leaching, placing the remaining solids in a vessel containing 15-20 grams per liter of activated carbon and adding 1 gram of sodium cyanide per liter of sludge to a sludge density of 30%. solids at a pH of 10.5. The mud was stirred for 24 hours and then the solids and activated carbon were analyzed separately to determine the level of gold extraction. The test results for the individual ores are tabulated in Table 2 and graphically shown in Figures 2 and 3. As can be seen in Table 2 and in Figures 2 and 3, gold recovery is significantly increased as that the grind size is reduced for individual ores. The test results for the RC # 1 composite material are tabulated in Table 3 and shown graphically in Figure 4. Again, gold extraction generally increases with the reduction in grinding size. In addition, however, the results of the RC # 1 ore compound show that the increased extraction of gold with very fine particles can not be explained simply through the release of additional gold, since gold extractions continue to increase significantly. even after the oxidation of sulfur sulfur reaches 95% by weight. Gold extractions greater than about 80% by weight are not obtained until the oxidation of the sulfur sulfide is greater than about 96%. Also, high gold extractions obtained above about 96% sulfur sulfide oxidation do not appear to be due solely to the increased oxidation of organic carbon. Rather, it appears that the remaining non-oxidized organic carbon is a little passivated to reduce the activity of the activated carbon as an adsorbent for gold, thus reducing the ability of the organic carbon to be degraded.

Ni O TABLE 1 Attributes of Individual Mena and Compound Material of Ore 4-- (1) Grams per normal ton (2) Mixed ore material made of 65.0% by weight of MC, 19.6% of US, 12.5% by weight of HGO, and 2.9% by weight of DZ t-J o TABLE 2 Different Grounds for Individual Ores (1) t (1) Autoclave conditions: 200-225 ° C, oxygen overpressure 345-690 kPa, retention 90-120 minutes, 30-40% solids in the sludge (2) 80% by weight of the smaller sample than the size in microns shown (3) Kilograms per normal ton of ore t O TABLE 3 Different Grounds for Composite Material of RC # 1 (1) t OS (1) Autoclave conditions: 225 ° C, oxygen overpressure 345-690 kPa, retention 120 minutes, 30% solids in the sludge (2) 80% by weight of the sample smaller than the size in microns shown EXAMPLE 2 This example shows the effect of the oxidation temperature under pressure on the recovery of gold. The tests were performed on samples of the composite material RC # 1 at different temperatures for a grinding size of approximately P80 = 10 microns. The test procedure is the same as that used in Example 1. Quad 4 tabulates the results, which are also shown graphically in Figure 5. The results show that higher temperatures generally result in higher gold recoveries. Again, the increased gold recoveries are not due to the release of additional gold through the extraction of additional sulfur sulfur, since the oxidation of sulfur sulfur is substantially complete in all tests. Rather, the increased recovery of gold appears to be due to benefits obtained through the treatment of organic carbon to oxidize and / or passivate the organic carbon after the substantially complete oxidation of the sulfur sulfide.

NJ to TABLE 4 Temperature in the Autoclave (1) Autoclave conditions: particles sized at P80 = 10μ, oxygen overpressure 690kPa, retention 120 minutes, 40-50% solids in the mud t 00 EXAMPLE 3 This example shows the effect of free acid in the oxidized mud in the recovery of gold. Several tests were carried out using the composite samples RC # 1. The tests were performed according to the same procedure of Example 1, except that different amounts of sulfuric acid were added to the final mud in the open autoclave, resulting in Thus, different levels of free acid in the autoclave discharge after oxidation under pressure, the results of the tests are tabulated in Table 5 and are shown graphically in Figure 6. Gold recoveries generally increase with the increase in free acid in the autoclave discharge Once again, the increase in gold recoveries, even after substantially completing the sulfur sulfide oxidation, has been achieved by indicating an oxidation / passivation benefit of the organic carbon treatment after substantially completing the oxidation of sulfur sulfur. to to O TABLE 5 Free Acid in the Autoclave Discharge Composite Material RC # 1 (1) O (1) Autoclave conditions: particles sized at P80 = 10μ, 225 ° C, oxygen overpressure 690 kPa, retention 120 minutes (2) Kilograms per normal tonne of ore (3) Grams of free acid per liter of liquid in mud rusted out of the autoclave EXAMPLE 4 This example shows the netting of the ability of the pregnant organic waste. Two ores were tested, one MC ore and one US ore. The samples of the ore were sized at P80 = 20 to 22 microns and subjected to oxidation under pressure at 225 ° C and at an overpressure of 690 kPa. The oxidation under pressure occurred in a continuous four-stage stirred autoclave, taking solid samples from the autoclave feed, from each of the 1-4 stages of the autoclave, and from the autoclave discharge. A leaching solution was prepared, using 10 kilograms of deionized water, 10 grams of sodium hydroxide and 2.50 grams of sodium cyanide. A normal gold solution was prepared by mixing 750 milliliters of deionized water with 0.25 grams of sodium hydroxide, 0.25 grams of sodium cyanide and 100 grams of 1004 ppm by weight of a gold chloride solution. The deionized water was then added to bring the volume of normal solution of total gold to 1 liter. To a 10 gram solid sample, 100 grams of a leaching solution was added and mixed thoroughly in a shaker for 24 hours. After, 10 milliliters of the solution were removed in a pipette and analyzed for gold using atomic absorption. Then, 10 milliliters of normal gold was added to the slurry to provide a gold seed, the sludge was then stirred on a shaker for 10 minutes. The sludge was then allowed to settle and placed through a pipette into a sample of 10 milliliters of sol ution and analyzed for gold using atomic adsorption. In this way, the ability of the solid samples for pregnant thinning was determined, and was calculated as grams of gold that were adsorbed from the gold seed per normal ton of ore. The test results are tabulated in Table 6. The results for the MC ore are shown graphically in Figure 7, and the results for the US ore are shown in Figure 8. As can be seen in Table 6 and in the Figures 7 and 8, the ability for the pregnant discharge of the samples for each ore, generally decreases as the oxidation under continuous pressure, indicating a significant benefit of the oxidation and / or passivation of the organic carbon in the ores. t tO TABLE 6 Organic Carbon Activity (1) «---- > (--- • (1) Autoclave conditions: dimensioned at P80 = 20 to 22 μ, 225 ° C, oxygen overpressure 690 kPa, retention time 103 minutes for MC and 70 minutes for US, 40% solids in the Mud (2) Grams of Au per normal ton of ore Various embodiments of the present invention have been described in detail. It must be recognized that any of the elements of these described modalities can be combined in any combination with elements of any other modality. In addition, modification and adaptation of the described modalities will be apparent to those skilled in the art. It should be expressly understood that such modifications and adaptations are within the scope of the present invention as set forth in the following claims.

Claims

CLAIMS 1. - A method to process a mineral material, which has a precious metal to reduce the potential for problems with the recovery of the precious metal when organic carbon is present, the method comprising the steps of: (a) providing a feed sludge that has particulate mineral material made from mud with an aqueous liquid, wherein (i) said mineral material comprises a precious metal selected from the group consisting of gold, silver and combinations thereof, and organic carbon, which has the ability to interfere with the recovery of the precious metal, said mineral material also comprises a sulfur sulfide in association with said precious metal and from which the precious metal is difficult to separate, and (ii) at least 80% by weight of the precious metal particles. said mineral material in the feed sludge is smaller than 38 microns in size, which facilitates the oxidative treatment of the mineral material to reduce r the ability of said organic carbon to interfere with the recovery of the precious metal; and (b) oxidatively treating said mineral material in the feed slurry comprising subjecting the feed sludge to an oxidation environment at a temperature greater than about 190 ° C to produce an oxidized sludge, wherein the ability of said sludge organic to interfere with the recovery of said precious metal from the oxidized sludge is reduced; wherein, during the oxidative treatment of said feed sludge, at least 96% of the sulfur sulfide in the feed slurry is oxidized, thus allowing substantial passivation of the organic carbon to reduce the ability of said organic carbon to interfere with the recovery of said precious metal. 2 - . 2 - The method according to claim 1, for the processing of a mineral material, wherein: said organic carbon has an affinity as an adsorbent of at least one of said precious metals, a salt of said precious metal, and a complex of said precious metal with a ligand, said affinity is capable of interfering with the recovery of the precious metal; and during said subjection, said affinity of the organic carbon is reduced. 3. The method according to claim 1, for the processing of a mineral material, wherein: during said oxidizing treatment, less than about 60% by weight of said organic carbon is oxidized and the organic carbon that is not oxidized is passivated as an adsorbent to reduce the ability of said organic carbon to interfere with the recovery of said precious metal. 4. The method according to claim 1, for the processing of a mineral material, wherein: said mineral material comprises more than about 0.3% by weight of the organic carbon. 5. The method according to claim 1, for the processing of a mineral material, wherein: said mineral material comprises more than about 0.6% by weight of the organic carbon. 6. The method according to claim 1, for the processing of a mineral material, wherein: at least about 80% by weight of said particles of the mineral material in the feed sludge are smaller than about 30 microns in size. 7. The method according to claim 1, for processing a mineral material, wherein: at least about 80% by weight of said particles of the mineral material in the feed sludge are smaller than about 20 microns in size. 8. The method according to claim 1, for the processing of a mineral material, wherein: the liquid of said oxidized sludge has a pH less than about a pH of 1.5. 9. The method according to claim 1, for the processing of a mineral material, wherein: said oxidizing treatment of the mineral material comprises subjecting said feed sludge to an oxidation environment at a temperature greater than about 200 ° C. 10. The method according to claim 1, for the processing of a mineral material, wherein: said oxidizing treatment of the mineral material comprises subjecting said feed sludge to an oxidation environment at a temperature greater than about 210 ° C. 11. The method according to claim 1, for the processing of a mineral material, wherein: said oxidizing treatment of the mineral material comprises subjecting said feed slurry to an oxidation environment at a temperature greater than about 220 ° C. 12. The method according to claim 1, for the processing of a mineral material, wherein: said oxidizing treatment of the mineral material comprises subjecting said feed sludge to an oxidation environment at a temperature of about 205 ° C to about 260 ° C. 13. The method according to claim 1, for the processing of a mineral material, wherein: said oxidizing treatment of the mineral material comprises subjecting said feed slurry to oxygen gas at an elevated pressure. 14. The method according to claim 1, for the processing of a mineral material, wherein: after the oxidative treatment of the mineral material, said precious metal is contacted with a ligand to form a complex of said precious metal with said ligand; and said precious metal is then removed from the complex and a solid metal product comprising said precious metal is prepared. 15. The method according to claim 1, for the processing of a mineral material, wherein: the provision of said feed sludge comprises shredding the coarse mineral material to produce said particles of the mineral material. 16. The method according to claim 1, for the processing of a mineral material, wherein: said mineral material comprises a complete ore. 17. The method according to claim 1, for the processing of a mineral material, wherein: the method is conducted substantially in the absence of a material containing added chlorine. 18. The method according to claim 1, for the processing of a mineral material, wherein: said method is substantially in the absence of calcination of said mineral material. 19 - The method according to claim 1, for the processing of a mineral material, wherein: during said oxidation treatment, the feed slurry is subjected to the oxidation environment for a time of about 20 minutes to about 120 minutes. 20.- A method for the processing of a mineral material that has a precious metal to facilitate the recovery of the precious metal reducing the potential of recovery problems when both the sulfide material and the organic carbon make the refractory material for the recovery of the metal precious, the method comprising the steps of: (a) providing a feed slurry having particulate mineral material made from sludge with an aqueous liquid, wherein (i) said mineral material comprises a precious metal selected from the group consisting of gold , silver and combinations thereof; sulfur material, which has sulfur sulfur in association with said precious metal and from which the precious metal is difficult to separate to allow recovery of the precious metal; and organic carbon, which has the ability to interfere with the recovery of the precious metal, and (ii) at least 80% by weight of the particles of said mineral material in the feeding mud are smaller than 38 microns in size , which facilitate the oxidative treatment of the mineral material to reduce the ability of said organic carbon to interfere with the recovery of the precious metal; and (b) oxidizing said mineral material, which comprises subjecting the feed sludge to an environment to produce an oxidized sludge, wherein during the subjection of said sludge to an oxidation environment, at least 96% of said sludge is oxidized. Sulfur sulfur in the feed slurry is oxidized, so that the precious metal is released from the association with the sulfur sulfur and the ability of said organic carbon to interfere with the recovery of said precious metal, is reduced. 21. The method according to claim 20, for the processing of a mineral material, wherein: during the oxidation treatment of said mineral material, at least a portion of, but less than all organic carbon is oxidized and the remaining non-oxidized organic carbon is passivated to reduce the ability of said remaining organic carbon to be oxidized to interfere with the recovery of said precious metal. 22. The method according to claim 20, for the processing of a mineral material, wherein: during said oxidation treatment of the mineral material, less than about 60% by weight of said organic carbon is oxidized. 23. The method according to claim 20, for the processing of a mineral material, wherein: during said treatment of oxidation of the mineral material, from about 10% by weight to about 40% by weight of said organic carbon is oxidized . 24 - The method according to claim 20, for the processing of a mineral material, wherein: said mineral material comprises more than about 2% by weight of sulfur sulfur. 25. - The method according to claim 20, for the processing of a mineral material, wherein: said mineral material comprises more than about 4% by weight of sulfur sulfur. 26. The method according to claim 20, for the processing of a mineral material, wherein: said mineral material comprises more than about 0. 4% by weight of organic carbon. 27. The method according to claim 20, for the processing of a mineral material, wherein: the liquid of said oxidized sludge comprises more than about 10 grams of free acid per liter of said liquid. 28. The method according to claim 27, for the processing of a mineral material, wherein: said free acid comprises free sulfuric acid. 29. The method according to claim 28, for the processing of a mineral material, wherein: said mineral material comprises a mixture of a first material comprising a carbonate mineral and at least one other material comprising sulfur sulfur , so that said mineral material comprises sufficient sulfur sulfur to allow the production of sufficient acid during said oxidation under pressure to provide said free acid in the oxidized sludge. 30. The method according to claim 20, for the processing of a mineral material, wherein: the liquid of said oxidized sludge comprises more than about 15 grams of free acid per liter of said liquid. 31 - The method according to claim 20, for the processing of a mineral material, wherein: at least about 80% by weight of said particles of the mineral material in the inlet mud are smaller than about 30. microns in size. 32. The method according to claim 20, for the processing of a mineral material, wherein: at least about 80% by weight of said particles of the mineral material in the feed sludge are smaller than about 20 microns in size The method according to claim 20, for the processing of a mineral material, wherein: said oxidizing treatment of the feed sludge comprises subjecting said feed sludge to an oxidation environment at a temperature greater than about 190 ° C. . 34 - The method according to claim 20, for the processing of a mineral material, wherein: said oxidizing treatment of the feed slurry comprises subjecting said feed slurry to an oxidation environment at a temperature greater than about 200 ° C. 35. The method according to claim 20, for the processing of a mineral material, wherein: said oxidizing treatment of the feed sludge comprises subjecting said feed sludge to an oxidation environment at a temperature greater than about 210 ° C. 36.- The method according to claim 20, for the processing of a mineral material, wherein: said oxidizing treatment of the feed sludge comprises subjecting said feed sludge to an oxidation environment at a temperature greater than about 220 ° C . 37. The method according to claim 20, for the processing of a mineral material, wherein: the method further comprises separating said gold from the oxidized mud and preparing a metal product comprising said precious metal. 38 - The method according to claim 20, for the processing of a mineral material, wherein: said separation of the precious metal from said oxidized sludge comprises contacting said precious metal with a cyanide to form a complex of said precious metal with said cyanide. 39.- A method for processing a mineral material that carries gold, which is refractory due to the presence of both organic carbon and sulfide material, to release gold from the sulfide material and to deactivate, or passivate, organic carbon present in the mineral material as an adsorbent capable of interfering with the recovery of the gold, the method comprising the steps of: (a) providing a feed slurry having a particulate mineral material that is made of sludge with an aqueous liquid, wherein (i) said mineral material comprises gold, sulfur material, which has sulfur sulfur, which is associated with gold and from which said gold is difficult to separate to allow gold recovery; and carbonaceous organic material, which is active as an adsorbent of a complex of said gold with a ligand and is capable of interfering with the recovery of said gold, and (ii) at least 80% by weight of the said particles. mineral material in the feeding mud are smaller than 38 microns, which facilitates the oxidative treatment of said mineral material to reduce the ability of the organic carbonaceous material to interfere with the recovery of said gold; and (b) the oxidative treatment of said mineral material comprising subjecting the feed sludge to an oxidation environment at a temperature greater than about 190 ° C, a total pressure greater than about 13.35 kg / cm2, and an overpressure of oxygen gas greater than about 1.7575 kg / cm2 to produce an oxidized sludge having more than 10 grams of free acid per liter of liquid in the oxidized sludge, wherein during said oxidation treatment, at least 96% of the sulfur sulfide in said Oxidized sludge is oxidized, and the organic carbon in the feed slurry is passivated as an adsorbent of said complex. The method according to claim 39, for the processing of a mineral material, wherein: said oxidized sludge has more than about 15 grams of free acid per liter of liquid in the oxidized sludge. 41. The method according to claim 39, for the processing of a mineral material, wherein: said mineral material comprises a mixture of a first material having a carbonate mineral and at least one other material having its sulfur lfuro, so that said mineral material comprises sufficient sulfur sulfur to allow the production of sufficient acid during said oxidation under pressure to provide said free acid in the oxidized sludge. 42. The method according to claim 39, for the processing of a mineral material, wherein: said feed sludge substantially comprises no acid added before said oxidation under pressure. 43.- The method according to claim 39, for the processing of a mineral material, wherein: said oxidation treatment of the mineral material comprises subjecting the feed sludge to an oxidation environment at a temperature greater than about 200 °. C, a total pressure greater than 17.57 kg / cm2 and an overpressure of oxygen gas or greater than about 1.7575 kg / cm2. 44. - The method according to claim 39, for the processing of a mineral material, wherein: said oxidation treatment of the mineral material comprises subjecting the feed sludge to an oxidation environment at a temperature greater than about 220 ° C, a total pressure greater than about 26,714 kg / cm2a and an oxygen gas overpressure greater than about 3.515kg / cm 2m. SUMMARY A process is provided for the treatment of ores containing refractory precious metal, particularly ores that carry gold, to reduce the ability of organic carbon to interfere with the recovery of the precious metal. Ore also contains sulfur materials with which gold is associated and from which gold is difficult to separate. The ore is shredded (104) to a size at which at least about 80% of the ore is smaller than about 40 microns in size. The crumbled ore is then made sludge and subjected to oxidation under pressure (108) under severe operating conditions. The treatment temperature is greater than about 190 ° C. When sulfide minerals are present, substantially all of the sulfur sulfur must first be oxidized before obtaining a significant benefit from organic carbon treatment. More than 96% of the sulfur sulfide must be oxidized. The neutralization (14) occurs after the oxidation treatment to prepare the sludge for cyanidation CI P (18) from which the gold (128) is then recovered.