Biological oxidation-suspension oxidation roasting pretreatment-supercritical CO2 leaching method for refractory gold ore

Abstract

The invention discloses a biological oxidation-suspension oxidation roasting pretreatment-supercritical CO2 leaching method for refractory gold ore, and belongs to the technical field of mineral processing and metallurgy. According to the method, sulfide and arsenide in the gold ore are oxidized by adopting microbial flora in an acid environment, then the ore subjected to biological oxidation is subjected to suspension oxidizing roasting at high temperature, and supercritical CO2 and sodium cyanide are used for combined leaching, so that the solubility and the leaching rate of gold are improved, the recovery rate of gold is remarkably improved, and the method is suitable for industrial production. Meanwhile, environmental pollution caused by a traditional cyanide method is reduced. Through the combined process of biological oxidation, suspension oxidation roasting and supercritical CO2 leaching, the recovery rate of gold is greatly increased, the use of cyanide and the emission of harmful waste are reduced, the environmental protection requirement of the green mining industry is met, meanwhile, the resource utilization is optimized through the integrated technological process, the overall production cost is reduced, and the method is suitable for industrial production. And energy and consumption of chemical reagents are saved, and the method is particularly suitable for refractory gold ores.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mineral processing and metallurgy, and relates to a method for treating refractory gold ore by biological oxidation-suspension oxidation roasting pretreatment-supercritical CO2 leaching, in particular to efficient recycling of refractory gold ore resources by a combined process of biological oxidation, suspension oxidation roasting, and supercritical CO2 leaching, while reducing the environmental impact of cyanide leaching and the environmental cost of the process. BACKGROUND

[0002] With the decreasing of easily treated gold ore resources worldwide, refractory gold ore has become the main raw material for cyanide gold extraction in gold production enterprises. Refractory gold ore refers to gold ore containing carbon or high-arsenic high-sulfur compounds that must be pretreated before being effectively extracted by cyanidation. When S, As, C, and other elements are contained in refractory gold ore, direct cyanide leaching of the raw ore has very poor leaching effect, and the leaching rate will not exceed 25%. Pretreatment processes can effectively break the wrapping of gold-bearing minerals or other gangue minerals on fine gold particles, and eliminate the "gold robbing" effect of carbonaceous materials, which is an effective way to improve the gold leaching rate of refractory gold ore and achieve efficient utilization of refractory gold ore.

[0003] Common pretreatment processes for refractory gold ore include roasting (such as the method for pretreating and extracting gold from refractory gold ore disclosed in patent CN116103505A), pressure oxidation (such as the method for improving the cyanide leaching rate of double refractory gold ore disclosed in patent CN112662886A), biological oxidation (such as the method for improving the biological oxidation speed of micro-fine particle level wrapped refractory gold ore disclosed in patent CN110669929A, and the method for interactive heap biological oxidation and gold extraction of refractory gold ore disclosed in patent CN113122731A), and chemical methods (such as the method for recovering gold and copper from oxygen-sulfur mixed copper-arsenic containing refractory gold ore disclosed in patent CN114774687A).

[0004] High-temperature roasting technology is currently widely used in the pretreatment stage of refractory gold ores. It can decompose sulfides and other harmful substances in gold ore through high-temperature oxidation. However, this technology has high operational requirements and is prone to over-roasting, under-roasting, and other adverse phenomena. Moreover, the roasting process may produce harmful gases such as sulfur dioxide and nitrogen oxides, which may cause environmental pollution if emissions are not properly controlled. Pressure oxidation accelerates the oxidation process of sulfides in ore by increasing pressure and temperature, thereby improving the leaching of gold in gold ore, especially showing good treatment effect on sulfide gold ores. However, pressure oxidation requires high-temperature and high-pressure conditions, resulting in high energy consumption, increased operating costs, and high equipment requirements. It also has poor selective oxidation of ore and is prone to problems under high-temperature and high-pressure conditions. Side reactions occur; biological oxidation, as a green, environmentally friendly, and low-energy-consumption gold ore pretreatment process, is particularly suitable for the treatment of low-grade and insoluble gold ores. However, its long reaction time and limited oxidation efficiency pose certain challenges to its large-scale industrial application. Cyanide leaching is currently the most important method for gold ore extraction both domestically and internationally. However, traditional cyanide leaching methods have many problems when treating difficult-to-process gold ores. Cyanide itself is highly toxic. If it leaks or is accidentally discharged into the environment during the treatment process, it will cause serious pollution to water sources, soil, and organisms, threatening the ecological environment and human health. The wastewater generated after cyanide extraction contains a large amount of cyanide and heavy metals, requiring complex treatment processes to meet environmental emission standards, which increases treatment costs. Summary of the Invention

[0005] This invention provides a method for processing refractory gold ore. By combining bio-oxidation treatment, suspension oxidation roasting pretreatment, and supercritical CO2 leaching technology, it effectively improves the gold recovery rate in gold ore and significantly reduces environmental pollution and resource waste. The technical path of this invention includes bio-oxidation pretreatment of refractory gold ore, suspension oxidation roasting process, and efficient gold leaching via supercritical CO2.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for pretreatment of refractory gold ore by bio-oxidation-suspension oxidation roasting-supercritical CO2 leaching includes the following steps:

[0008] Crushing and grinding: crushing and grinding refractory gold ore to obtain powder with uniform particle size;

[0009] Slurry conditioning: The powder is prepared into a slurry, and the pH of the slurry is adjusted using an acidic solution;

[0010] Biological oxidation: The bacterial strain is cultured in a culture medium at a set temperature, pH, and oxygen concentration; then the cultured strain is inoculated into the mineral slurry to initiate a reaction; after the reaction, sedimentation separation, slurry treatment, and microbial recycling are carried out sequentially; the oxygen concentration is controlled at 20%~30%;

[0011] washing and drying: washing and drying the oxidized ore slurry, and the dried product is used as the suspension oxidation roasting raw material;

[0012] suspension oxidation roasting: placing the suspension oxidation roasting raw material into a suspension roasting furnace, introducing oxygen into the suspension roasting furnace, and roasting the raw material at a set temperature to obtain a roasting product;

[0013] supercritical CO2 cyanide leaching: sending the roasting product into a supercritical CO2 cyanide leaching system for supercritical CO2 cyanide leaching;

[0014] filtration and washing: filtering and washing the leached material to obtain a gold-containing pregnant solution and a cyanide tailing.

[0015] The refractory gold ore contains Au 0.5g / t-5.0g / t, and also contains C 0.2%~15.0%, As 0.1%~2.0%, and S 4%~11% by mass;

[0016] The refractory gold ore is crushed by a jaw crusher, a hammer crusher or an impact crusher to a particle size of not more than 12mm.

[0017] The powder obtained after grinding has a particle size of not more than 0.074mm.

[0018] During the ore slurry adjustment process, the solid content of the ore slurry is 30%~40%, the acidic solution is a sulfuric acid solution, the pH of the ore slurry is adjusted to 1.5~3.0, and the oxygen concentration in the ore slurry is greater than 20%;

[0019] The culture medium contains sulfate and iron salt; during the culture process, the culture temperature is 30℃~40℃, the pH is 1.5~3.0, and the oxygen concentration is 20%~30%;

[0020] The inoculation amount of the bacteria is 0.5%~2% of the volume of the ore slurry; and the biological oxidation reaction time is 7~40 days.

[0021] During the biological oxidation process, the bacteria are uniformly distributed in the ore slurry by stirring or gas aeration;

[0022] The water content of the suspension oxidation roasting raw material is 4%~10%;

[0023] During the suspension oxidation roasting process, the roasting temperature is 500℃~900℃, and the roasting time is 0.5h~2h;

[0024] In the supercritical CO2 cyanide leaching process, CO2 is first pressurized and heated until the temperature and pressure of CO2 are at the critical point, and then the roasted product is sent to the supercritical CO2 cyanide leaching system for leaching, and the reaction occurs under the action of supercritical CO2 to generate gold cyanide complex;

[0025] The working pressure is 8MPa~40MPa, and the working temperature is 35℃~80℃.

[0026] The CO2 flow rate during leaching is 5L / min~200L / min.

[0027] The key points of the present application are as follows:

[0028] 1. Biological oxidation pretreatment: A specific microbial flora is used to oxidize sulfides and arsenides in gold ore in an acidic environment to release gold and improve the leachability of gold.

[0029] 2. Suspension oxidation roasting: By suspending and oxidizing the biologically oxidized ore at high temperature, the carbonaceous matter (graphite and organic carbon) in the refractory gold ore can be oxidized or lose activity, and the gold-bearing sulfides (pyrite and arsenopyrite), quartz and other substances can be destroyed to expose the fine gold particles to the maximum extent. The gas escaping during roasting produces micropores, which is beneficial to the diffusion of leaching agent and further enhances the leaching effect of gold.

[0030] 3. Supercritical CO2 leaching: The combination of supercritical CO2 and sodium cyanide leaching improves the solubility and leaching rate of gold, significantly improves the recovery rate of gold, and reduces the environmental pollution of traditional cyanidation.

[0031] The beneficial effects of the present application are as follows:

[0032] 1. High recovery rate: The combination of biological oxidation, suspension oxidation roasting and supercritical CO2 leaching significantly improves the recovery rate of gold, especially for refractory gold ore.

[0033] 2. Strong environmental protection: The use of supercritical CO2 leaching reduces the use of cyanide and the discharge of harmful waste, meeting the environmental protection requirements of green mining.

[0034] 3. Energy saving and consumption reduction: The integrated process flow optimizes resource utilization, reduces overall production cost, and saves energy and chemical reagent consumption. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The process flow chart of the present application. DETAILED DESCRIPTION

[0036] The application provides a method for treating refractory gold ore by biological oxidation-suspension oxidation roasting pretreatment-supercritical CO2 leaching. Figure 1 The specific implementation scheme is as follows.

[0037] I. Crushing and grinding: the refractory gold ore is crushed and ground into powder with uniform particle size. The primary crushing of the refractory gold ore is to crush the bulk ore to a particle size of not greater than 12 mm, and a jaw crusher, a hammer crusher or an impact crusher is usually used for primary crushing. The crushed ore has uniform particle size, which facilitates subsequent grinding and pretreatment; the particles of the crushed ore are screened to separate ore blocks with a particle size greater than 12 mm for secondary crushing, so as to ensure that the ore meets the requirements of subsequent grinding; the purpose of grinding is to further reduce the particle size of the ore particles, increase the surface area of the ore in contact with the microorganisms, and promote the biological oxidation reaction. The grinding process is mainly carried out by grinding equipment. The gold ore is ground to a particle size of 0.074 mm or less, which can maximize the exposure of the gold content on the surface of the ore and enhance the effect of the microbial oxidation reaction. The refractory gold ore contains 0.5 g / t to 5.0 g / t of Au, 0.2% to 15.0% of C, 0.1% to 2.0% of As, and 4% to 11% of S.

[0038] II. Slurry adjustment: after grinding and screening, the slurry is appropriately adjusted according to the needs of the subsequent biological oxidation process. The solid content of the slurry is usually maintained at 30% to 40%, and a too high concentration will cause difficulty in oxygen transfer, and a too low concentration will waste materials and chemical reagents. According to the properties of the ore and the fineness after grinding, the concentration of the slurry can be appropriately adjusted to ensure good contact between the ore and the microorganisms and promote the efficient biological oxidation; in the biological oxidation process, the pH value of the slurry needs to be maintained in the acidic range (pH 1.5-3.0), and the pH value is adjusted by adding an acidic solution (such as sulfuric acid) to ensure the activity of the microorganisms and the oxidation reaction. The biological oxidation process requires sufficient oxygen supply: the oxygen concentration in the slurry is greater than 20% to ensure the activity of the microorganisms, and the oxygen solubility can be increased by means of gas aeration and pressurization to optimize the oxidation process.

[0039] III. Bio-oxidation: After the ore slurry is adjusted to the optimal conditions, the selected bacteria are cultured in a suitable medium (such as a medium containing sulfate and iron salts). During the culture, the appropriate temperature (generally between 30°C and 40°C), pH (usually between 1.5 and 3.0), and oxygen concentration (20%~30%) are maintained to promote the growth and reproduction of the microorganisms. When the microorganisms in the culture medium reach the optimal activity, they are inoculated into the ground ore slurry, usually at a volume of 0.5%-2% (v / v) of the ore slurry, and are uniformly distributed in the ore slurry by stirring or gas aeration. In this process, the microorganisms oxidize the sulfides in the ore through their metabolic action, converting the gold in the gold ore into a more easily leachable soluble form. The bio-oxidation reaction usually lasts for 7~40 days, until most of the sulfides are gone and the leachability of gold is significantly improved. After the reaction is complete, the ore slurry is subjected to sedimentation separation, ore slurry treatment, and microbial recovery and reuse, etc.

[0040] IV. Washing and drying: After the bio-oxidation treatment of the gold ore is completed, the sulfides in the ore have been oxidized by the microorganisms into soluble oxides or sulfates, and the gold in the gold ore has been converted into a form that is easy to leach. In order to further improve the recovery efficiency of gold and prepare for the next step of suspension oxidation roasting and supercritical CO2 leaching, the bio-oxidized ore slurry must be washed and dried. This step aims to remove excess dissolved salts, unreacted minerals, microbial residues, and impurities, ensuring the smooth progress of the subsequent process. The washing process needs to be reasonably controlled in terms of water quantity, washing time, and washing temperature to ensure the removal effect of impurities and insoluble substances. Although the washed minerals have removed most of the impurities and dissolved salts, they still contain a certain amount of water. Before entering the next step of suspension oxidation roasting pretreatment process, the ore needs to be dried to reduce the moisture content of the material, facilitating the subsequent roasting process. After drying, the final suspension oxidation roasting raw material with a water content of 4%~10% is obtained.

[0041] Five, suspension oxidation roasting: oxidation roasting is a widely used gold ore pretreatment process, through the appropriate conditions of roasting, can make the organic carbon, graphite carbon and other gold robbing substances in gold ore are burned out, eliminate the "gold robbing" effect; in the process of roasting, quartz and other gold wrapped mineral crystal structure changes, porosity increases, is conducive to gold and leaching agent contact; carbonate and other minerals in the decomposition process when the gas escapes, produce a large number of microporous, conducive to the leaching of gold. The roasting process roasting atmosphere is air, air into the suspension roasting furnace to make the gold ore powder in suspension state; the roasting temperature needs to be determined according to the specific properties of gold ore, sulfide and oxidation degree of the type, usually, the temperature is controlled between 500 ℃~900 ℃, too high temperature may lead to the destruction of the structure of the mineral, while too low temperature may not be complete oxidation. The roasting time is generally 0.5h~2h, too short time may lead to incomplete oxidation, too long may cause sintering phenomenon, affect the subsequent leaching effect.

[0042] Six, supercritical CO2 cyanide leaching is one of the core innovative steps of the present application, by combining supercritical CO2 technology with cyanide leaching, the gold recovery rate is significantly improved, especially for those difficult to handle gold ore after biological oxidation and suspension oxidation roasting treatment; supercritical CO2 leaching can not only improve the leaching rate of gold, but also effectively reduce the impact on the environment, improve the green environmental protection of gold leaching process. Under the condition of supercritical CO2, gold (Au) in gold ore can form stable gold cyanide complex with cyanide (NaCN), the super high solubility and low surface tension characteristics of supercritical CO2 can accelerate the reaction rate of cyanide leaching, especially for the fine particles of gold in gold ore. The generation of supercritical CO2 is the first step of the process, in order to make CO2 reach supercritical state, CO2 needs to be pressurized and heated, so that its temperature and pressure reach the critical point; the gold ore slurry after suspension oxidation roasting is sent into the leaching reactor to ensure that the slurry is in full contact with supercritical CO2; under the action of supercritical CO2, gold in gold ore begins to react with cyanide to form stable gold cyanide complex. The whole leaching process needs a certain time and temperature to complete; after the end of the leaching reaction, gold cyanide complex solution will be produced in the reactor, and there will be residual supercritical CO2 and unreacted cyanide solution.

[0043] Seven, filtration and washing process: the leaching completed material is filtered and washed to obtain gold containing liquid and cyanide tailings.

[0044] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings. It should be pointed out that the examples described in the present application are only used to further explain and illustrate, not to limit the scope of application. Based on the present application, all other examples obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0045] In the following examples, jaw crusher, hammer crusher or impact crusher is used to crush the refractory gold ore; in the biological oxidation process, the bacteria are uniformly distributed in the ore slurry by stirring or gas aeration.

[0046] Example 1:

[0047] There are a large number of low-grade sulfide gold ore in a certain mining area, which contains a high content of iron sulfide and copper sulfide, and the content of gold in the gold ore is low, i.e. 0.5 g / t, and also includes C 3.6%, As 0.64%, S 5.78% in mass fraction. The ore is due to the presence of sulfide in the gold ore.

[0048] In this example, the gold ore is used as raw material, and the biological oxidation-suspension roasting pretreatment-supercritical CO2 cyanide leaching is carried out, including the following steps:

[0049] Crushing and grinding: the refractory gold ore is crushed to a particle size of not more than 12 mm, and then ground to obtain a uniform powder with a particle size of 0.074 mm or less;

[0050] Ore slurry adjustment: the powder is prepared into an ore slurry with a solid content of 35%, and the ore slurry is adjusted to pH=2.2 using a sulfuric acid solution, and the oxygen concentration in the ore slurry is 20%;

[0051] Biological oxidation: the Thiobacillus ferrooxidans bacteria group is placed in a culture medium containing sulfate and iron salt, and is cultured at 35℃, pH=2.2 and oxygen concentration of 25%. Then the cultured bacteria are inoculated into the ore slurry at a ratio of 1% of the volume of the ore slurry, so that the bacteria are uniformly distributed in the ore slurry, and the biological oxidation reaction is carried out at 35℃ and pH of 1.5-2.0. After 30 days of reaction, the sedimentation separation, ore slurry treatment and microbial recycling are carried out in turn;

[0052] Washing and drying: the ore slurry after biological oxidation is washed and dried, and the product is dried to a water content of 5% as a suspension oxidation roasting raw material;

[0053] Suspension oxidation roasting: the suspension oxidation roasting raw material is placed in a suspension roasting furnace, oxygen is introduced into the suspension roasting furnace, the raw material is in a suspended state, the oxygen concentration is maintained at 100%, and the roasting is carried out at 850℃ for 1h to obtain a roasting product;

[0054] Supercritical CO2 cyanide leaching: CO2 is pressurized and heated to the critical point, and then the roasted product is sent to the supercritical CO2 cyanide leaching system for leaching, and the reaction occurs under the action of supercritical CO2 to generate cyanide complex. During the leaching process, the concentration of sodium cyanide is 0.3%, the pressure is 10 MPa, the temperature is 60 DEG C, the leaching time is 4 h, and the CO2 flow is 100 L / min.

[0055] Filtration and washing: the leached material is filtered and washed to obtain gold-containing pregnant solution and cyanide tailings, and then gold is recovered from the gold-containing pregnant solution by activated carbon adsorption method, and the recovery rate reaches 95%.

[0056] The gold recovery rate of the ore is improved to 95% by using the supercritical CO2 cyanide leaching method provided by the present application, which indicates that the combined pretreatment process of biological oxidation, suspension oxidation roasting and supercritical CO2 leaching significantly improves the leaching efficiency of gold.

[0057] Example 2:

[0058] The gold ore of a certain mining area contains high sulfur and arsenic, and the content of gold in the gold ore is 0.56 g / t, and the content of C, As and S is 7.4%, 0.96% and 6.24%, respectively.

[0059] This embodiment uses the gold ore as raw material to carry out biological oxidation-suspension roasting pretreatment-supercritical CO2 cyanide leaching, which includes the following steps:

[0060] Crushing and grinding: the refractory gold ore is crushed to a particle size of not more than 12 mm, and then ground to obtain uniform powder with a particle size of 0.074 mm or less;

[0061] Slurry adjustment: the powder is prepared into a slurry with a solid content of 30%, and the slurry is adjusted to pH=2.0 by using sulfuric acid solution, and the oxygen concentration in the slurry is 25%;

[0062] Biological oxidation: the Thiobacillus ferrooxidans bacterial group is placed in a culture medium containing sulfate and iron salt, and cultured in an environment of 36 DEG C, pH=2.0 and oxygen concentration of 20%; then the cultured bacteria are inoculated into the slurry at a ratio of 0.5% of the volume of the slurry, so that the bacteria are uniformly distributed in the slurry, and the biological oxidation reaction is carried out at 30 DEG C and pH=2.0, and after 30 days of reaction, the slurry is sequentially subjected to sedimentation separation, slurry treatment and microbial recovery and reuse;

[0063] Washing and drying: the slurry after biological oxidation is washed and dried, and the dried product has a water content of 8%, which is used as a suspension oxidation roasting raw material;

[0064] suspension roasting: the suspension roasting raw material is placed in a suspension roasting furnace, oxygen is introduced into the suspension roasting furnace, the raw material is in a suspension state, the oxygen concentration is maintained at 90%, and the roasting product is obtained by roasting at 750℃ for 2h;

[0065] supercritical CO2 cyanide leaching: CO2 is pressurized and heated to the critical point, and then the roasting product is sent into a supercritical CO2 cyanide leaching system for leaching, and the reaction occurs under the action of supercritical CO2 to generate a gold cyanide complex. During the leaching process, the concentration of sodium cyanide is 0.4%, the pressure is 12 MPa, the temperature is 65℃, the leaching time is 5h, and the CO2 flow rate is 200L / min.

[0066] filtration and washing: the leached material is filtered and washed to obtain a gold-containing pregnant solution and a cyanide tailing, and then the gold-containing pregnant solution is recovered by an activated carbon adsorption method, and the recovery rate reaches 98%.

[0067] In the ore in this embodiment, gold mainly exists in sulfides, and arsenic-containing minerals have a strong inhibitory effect on cyanide leaching. The traditional cyanide leaching method has poor effect, and the gold recovery rate is improved to 98% by using the difficult-to-treat gold ore biological oxidation-suspension roasting pretreatment-supercritical CO2 cyanide leaching method provided by the present application, and the treatment of arsenic is effectively controlled, which ensures that the arsenic content in the leaching solution is lower than the environmental protection standard.

[0068] Example 3:

[0069] The gold ore produced in a certain mining area contains a high content of nickel (about 3%). Gold in this kind of ore mainly exists in the form of sulfides combined with nickel. The content of gold in the gold ore is 0.7g / t, and the content of C, As and S is 5.1%, 0.5% and 5.62% respectively. The ore contains sulfides due to the existence of sulfides in the gold ore.

[0070] In this embodiment, the gold ore is used as a raw material, and the biological oxidation-suspension roasting pretreatment-supercritical CO2 cyanide leaching is carried out, which includes the following steps:

[0071] crushing and grinding: the difficult-to-treat gold ore is crushed to a particle size of not more than 12mm, and then ground to obtain uniform powder with a particle size of 0.074mm or less;

[0072] slurry adjustment: the powder is prepared into a slurry with a solid content of 35%, and the slurry is adjusted to pH=2.0 by using a sulfuric acid solution, and the oxygen concentration in the slurry is 30%;

[0073] Bio-oxidation: Acidithiobacillus thiooxidans and Thiobacillus ferrooxidans are placed in a culture medium containing sulfate and ferric salt, and are cultured at 37℃, pH=2.0, and an oxygen concentration of 25%; then the cultured bacteria are inoculated into the ore slurry at a ratio of 1% of the volume of the ore slurry, so that the bacteria are uniformly distributed in the ore slurry, and bio-oxidation is carried out at 30℃ and pH=2.0; after 40 days of reaction, sedimentation separation, ore slurry treatment, and microbial recycling are sequentially performed;

[0074] Washing and drying: the ore slurry after bio-oxidation is washed and dried until the water content of the product is 5%, which is used as a suspension oxidation roasting raw material;

[0075] Suspension oxidation roasting: the suspension oxidation roasting raw material is placed in a suspension roasting furnace, oxygen is introduced into the suspension roasting furnace, the raw material is in a suspension state, the oxygen concentration is maintained at 95%, and the raw material is roasted at 800℃ for 2h to obtain a roasted product;

[0076] Supercritical CO2 cyanide leaching: CO2 is pressurized and heated until the temperature and pressure of CO2 are at the critical point, then the roasted product is sent into a supercritical CO2 cyanide leaching system for leaching, and gold cyanide complexes are generated under the action of supercritical CO2. During the leaching process, the concentration of sodium cyanide is 0.35%, the pressure is 25MPa, the temperature is 70℃, the leaching time is 4.5h, and the CO2 flow rate is 100L / min.

[0077] Filtration and washing: the leached material is filtered and washed to obtain a gold-containing liquid and a cyanide tailing, and then the gold-containing liquid is treated by an activated carbon adsorption method to recover gold, and the recovery rate reaches 96%.

[0078] Due to the strong mutual interference between nickel and gold elements, the traditional cyanide method often cannot effectively recover gold. The gold recovery rate of high-nickel gold ore is increased to 96% by using the bio-oxidation-suspension roasting pretreatment-supercritical CO2 cyanide leaching method provided by the present application, and the presence of nickel does not significantly affect the leaching of gold. The process significantly improves the recovery efficiency of gold ore and has good environmental protection.

[0079] Example 4:

[0080] The gold ore in a certain mining area contains a high proportion of iron (about 15%), and these iron minerals mainly exist in the form of sulfides and oxides. The gold content in the gold ore is 0.62g / t, and the mass fraction also includes C 9.5%, As 0.6%, and S 5.5%. The ore contains sulfides.

[0081] The embodiment takes the gold ore as raw material, and performs biological oxidation-suspension roasting pretreatment-supercritical CO2 cyanide leaching, including the following steps:

[0082] Crushing and grinding: the refractory gold ore is crushed to a particle size of not more than 12 mm, and then ground to obtain uniform powder with a particle size of 0.074 mm or less;

[0083] Slurry adjustment: the powder is prepared into a slurry with a solid content of 30%, and the slurry is adjusted to pH=2.0 by using a sulfuric acid solution, and the oxygen concentration in the slurry is 25%;

[0084] Biological oxidation: Thiobacillus ferrooxidans and Leptospirillum ferrooxidans bacteria are placed in a culture medium containing sulfate and iron salt, and are cultured at 35°C, pH=2, and an oxygen concentration of 25%; then the cultured bacteria are inoculated into the slurry at a ratio of 2% of the volume of the slurry, so that the bacteria are uniformly distributed in the slurry, and the biological oxidation reaction is carried out at 28°C and pH 1.8-2.0, and after 25 days of reaction, sedimentation separation, slurry treatment and microbial recycling are sequentially performed;

[0085] Washing and drying: the slurry after biological oxidation is washed and dried, and the product is dried to a water content of 10% as a suspension oxidation roasting raw material;

[0086] Suspension oxidation roasting: the suspension oxidation roasting raw material is placed in a suspension roasting furnace, oxygen is introduced into the suspension roasting furnace, the raw material is in a suspended state, the oxygen concentration is maintained at 90%, and the roasting is carried out at 850°C for 1 h to obtain a roasting product;

[0087] Supercritical CO2 cyanide leaching: CO2 is pressurized and heated to the critical point, and then the roasting product is sent into a supercritical CO2 cyanide leaching system for leaching, and reacts under the action of supercritical CO2 to generate gold cyanide complex. During the leaching process, the concentration of sodium cyanide is 0.3%, the pressure is 10 MPa, the temperature is 65°C, the leaching time is 4 h, and the CO2 flow rate is 100 L / min.

[0088] Filtration and washing: the leached material is filtered and washed to obtain gold-containing noble liquid and cyanide tailings, and then the gold-containing noble liquid is recovered by activated carbon adsorption method, and the recovery rate reaches 94%.

[0089] Due to the presence of iron minerals, the leaching of gold is often severely inhibited, and traditional cyanide leaching method is difficult to effectively extract gold. Iron minerals not only consume cyanide solution, but also form metal sulfides or metal complexes with gold in gold ore, resulting in low leaching efficiency of gold. The gold recovery rate of high-iron gold ore is increased to 94% by using the difficult-to-treat gold ore biological oxidation-suspension roasting pretreatment-supercritical CO2 cyanide leaching method for leaching, which significantly reduces the inhibition of iron minerals on the cyanide leaching process. In addition, through the steps of biological oxidation and suspension oxidation roasting, the consumption of cyanide solution by iron minerals is effectively reduced, and the overall processing efficiency is improved.

[0090] Example 5

[0091] The gold in a certain gold mine mainly exists in the form of oxidized minerals, and the ore also contains a high content of clay minerals and quartz. The content of gold in the gold mine is 1.5 g / t, and the content of C is 6.3%, the content of As is 0.7%, and the content of S is 7.8% by mass fraction. The ore is due to the presence of sulfides in the gold ore.

[0092] In this embodiment, the gold mine is used as raw material for biological oxidation-suspension roasting pretreatment-supercritical CO2 cyanide leaching, which includes the following steps:

[0093] Crushing and grinding: the difficult-to-treat gold ore is crushed to a particle size of not more than 12 mm, and then ground to obtain uniform powder with a particle size of 0.074 mm or less;

[0094] Slurry adjustment: the powder is prepared into a slurry with a solid content of 35%, and the slurry is adjusted to pH=3.0 by using sulfuric acid solution, and the oxygen concentration in the slurry is 30%;

[0095] Biological oxidation: Thiobacillus ferrooxidans and Leptospirillum ferrooxidans bacterial flora are placed in a culture medium containing sulfate and iron salt, and cultured in an environment of 40℃, pH=3.0 and oxygen concentration of 30%; then the cultured bacteria are inoculated into the slurry at a ratio of 1% of the volume of the slurry, so that the bacteria are uniformly distributed in the slurry, and the biological oxidation reaction is carried out at 30℃ and pH=2.0, after 35 days of reaction, the slurry is sequentially subjected to sedimentation separation, slurry treatment and microbial recovery and reuse;

[0096] Washing and drying: the slurry after biological oxidation is washed and dried, and the product is dried to a water content of 5% as a suspension oxidation roasting raw material;

[0097] Suspension oxidation roasting: the suspension oxidation roasting raw material is placed in a suspension roasting furnace, oxygen is introduced into the suspension roasting furnace, the raw material is in a suspended state, the oxygen concentration is maintained at 95%, and the roasting is carried out at 800℃ for 1h to obtain a roasting product;

[0098] Supercritical CO2 cyanide leaching: CO2 is pressurized and heated to the critical point of CO2 temperature and pressure, and then the roasted product is sent into a supercritical CO2 cyanide leaching system for leaching, and a reaction occurs under the action of supercritical CO2 to generate a gold cyanide complex. During the leaching process, the concentration of sodium cyanide is 0.25%, the pressure is 9 MPa, the temperature is 50 DEG C, the leaching time is 4 h, and the CO2 flow rate is 50 L / min.

[0099] Filtration and washing: the leached material is filtered and washed to obtain a gold-containing pregnant solution and a cyanide tailing, and then gold is recovered from the gold-containing pregnant solution by an activated carbon adsorption method, and the recovery rate reaches 92%.

[0100] Oxidized gold ore usually exhibits a low gold recovery rate, especially gold ore containing clay minerals, and due to the adsorption of the clay minerals to the cyanide leaching solution, the leaching effect of gold is not ideal. The leaching of the refractory gold ore by the method provided by the present application, i.e. biological oxidation-suspension roasting pretreatment-supercritical CO2 cyanide leaching, can improve the gold recovery rate of the complex oxidized gold ore to 92%. In particular, after the biological oxidation and suspension oxidation roasting treatment, the clay minerals in the ore no longer have a significant impact on the leaching of gold, and the leaching effect of gold is significantly improved.

Claims

1. A method of bio-oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ores, characterized in that, The method comprises the following steps: Crushing and grinding: crushing and grinding the refractory gold ore to obtain powder with uniform particle size; Slurry preparation: preparing the powder into slurry and adjusting the pH of the slurry by using an acidic solution; Bio-oxidation: culturing the bacteria in a culture medium at a set temperature, pH and oxygen concentration; then inoculating the cultured bacteria into the slurry to react; after the reaction, sequentially performing sedimentation separation, slurry treatment and microbial recycling; and controlling the oxygen concentration to be 20%-30%; Washing and drying: washing and drying the slurry after bio-oxidation, and taking the dried product as a suspension oxidation roasting raw material; Suspension oxidation roasting: placing the suspension oxidation roasting raw material into a suspension roasting furnace, introducing oxygen into the suspension roasting furnace, and roasting the raw material in a suspension state at a set temperature to obtain a roasting product; Supercritical CO2 cyanide leaching: sending the roasting product into a supercritical CO2 cyanide leaching system to perform supercritical CO2 cyanide leaching: first, pressurizing and heating CO2 to a critical point, and then sending the roasting product into the supercritical CO2 cyanide leaching system to leach, and generating gold cyanide complex under the action of supercritical CO2; Filtering and washing: filtering and washing the leached material to obtain a gold-containing precious liquid and a cyanide tailing.

2. A method for the bio-oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ores according to claim 1, characterized in that, In the supercritical CO2 cyanide leaching process, the working pressure is 8-40 MPa, and the working temperature is 35-80℃. In the leaching process, the CO2 flow rate is 5-200 L / min.

3. A method of bio-oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ore according to claim 2, characterized in that, In the process of culturing the bacteria, the culture temperature is 30-40℃, the pH is 1.5-3.0, and the oxygen concentration is 20%-30%.

4. A method of bio-heap oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ores according to claim 2 or 3, characterized in that, In the process of adjusting the slurry, the solid content of the slurry is 30%-40%, the pH of the slurry is adjusted to 1.5-3.0, and the oxygen concentration in the slurry is greater than 20%.

5. A method of bio-heap oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ores according to claim 2 or 3, characterized in that, In the bio-oxidation process, the inoculation amount of the bacteria accounts for 0.5%-2% of the volume of the slurry, and the bio-oxidation reaction time is 7-40 days.

6. A method of bio-oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ore according to claim 2 or 3, characterized in that, The water content of the suspension oxidation roasting raw material is 4%-10%.

7. A method of bio-heap oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ores according to claim 2 or 3, characterized in that, In the process of suspension oxidation roasting, the roasting temperature is 500-900℃, and the roasting time is 0.5-2 h.

8. A method of bio-oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ore according to claim 2 or 3, characterized in that, In the bio-oxidation process, the bacteria are uniformly distributed in the slurry by stirring or gas aeration.

9. A method of bio-oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ore according to claim 2 or 3, characterized in that, The refractory gold ore contains Au 0.5-5.0 g / t, and also contains C 0.2%-15.0%, As 0.1%-2.0% and S 4%-11% in terms of mass fraction.

10. A method of bio-oxidation-suspension oxidation roasting pretreatment- supercritical CO2 leaching of refractory gold ore according to claim 2 or 3, characterized in that, The refractory gold ore is crushed by using a jaw crusher, a hammer crusher or an impact crusher to a particle size of not greater than 12 mm. The particle size of the powder obtained after grinding is less than 0.074 mm.

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