Treatment method of pollutants in process of extracting gold from refractory gold concentrate by bio-oxidation carbon-in-pulp

Abstract

The application discloses a kind of refractory gold concentrate biological oxidation carbon-in-pulp gold extraction process pollutant processing method, by biological oxidation residue filter pressing washing, reduce the impurity ions such as iron, arsenic, polysulfide into carbon-in-pulp cyanidation process from source, source reduces the generation amount of pollutants such as ferricyanide, arsenic, thiocyanate;Biological oxidation residue is treated with hydrogen peroxide before carbon-in-pulp cyanidation, oxidize low-valence sulfur to sulfate ion, can reduce the generation amount of thiocyanate from source, reduce the amount of gold leaching agent.Carbon-in-pulp cyanidation is carried out with low-cyanide reagent, reduce the cyanide content in carbon-in-pulp tailings;Carbon-in-pulp tailings are filter pressed and washed, filter pressing liquid is returned to be used for oxidation residue slurry, re-enter cyanide leaching, make full use of the residual gold leaching agent in filter pressing liquid, and valuable elements such as gold and silver in filter liquid are recycled.The application uses biological oxidation liquid to treat carbon-in-pulp tailings washing liquid, reduces the cost of cyanide breaking treatment of carbon-in-pulp tailings washing liquid.

Description

Technical Field

[0001] The present invention relates to a method for treating pollutants in the field of environmental protection, and in particular to a method for treating pollutants in a process for leaching gold from refractory gold concentrate using bio-oxidation carbon. Background Art

[0002] Refractory gold ore refers to gold ore that cannot be effectively leached using conventional cyanide methods after fine grinding. It is generally defined as gold ore with a cyanide leaching rate of less than 80% after fine grinding. Currently, with the large-scale mining of gold resources, high-grade, easily leached gold ores are becoming increasingly scarce, and refractory gold ores are gradually becoming the main raw material for the gold industry. According to incomplete statistics, approximately 30% of China's proven gold reserves are refractory gold ores, and this proportion is expected to increase annually. Because the gold particles in this type of ore are often encapsulated by sulfides such as arsenopyrite and pyrite, and contain a high number of impurities such as non-metallic elements such as arsenic, sulfur, and carbon, and metallic elements such as copper and antimony, the traditional direct cyanide leaching process results in low gold leaching rates and high cyanide consumption. Therefore, refractory gold ores require pretreatment before leaching. Pretreatment methods mainly include oxidative roasting, pressure oxidation, and bacterial oxidation. Among them, the bio-oxidation pretreatment process has the advantages of simple operation, low production cost and easy control compared with other difficult-to-smelt gold extraction technologies, and is increasingly favored by production companies.

[0003] Because difficult-to-treat ores often contain minerals with high sulfur, arsenic, and iron content, they are easily oxidized during the biological oxidation process, producing an oxidation solution with high arsenic and iron concentrations and acidity, as well as an oxidation slag high in sulfur, arsenic, and iron. This slag, laden with impurities, consumes significant amounts of leaching reagents during the cyanide leaching process and produces secondary pollutants such as thiocyanate, ferrocyanate, and arsenic compounds. These pollutants must be controlled and treated during the production process to minimize their adverse impact on production indicators.

[0004] Currently, the oxidation solution and cyanide tailings produced during the bio-oxidation-carbon leaching process for gold extraction from difficult-to-treat gold concentrates are typically treated with the cyanide tailings slurry, achieving the goal of treating waste with waste. Chinese patent application CN108117232A discloses a method for detoxifying cyanide-containing tailings slurry using a bio-oxidation solution in a gold extraction process in the gold industry. This method involves adding a bio-oxidation solution to the cyanide-containing tailings slurry in a closed stirred reactor to remove easily released cyanide and metal cyanide complexes. The tailings slurry is then filtered or filter-pressed and then stored in a tailings pond. However, there is a risk of cyanide and arsenic dissolution during storage, and valuable elements such as gold and silver remaining in the tailings slurry cannot be recovered.

[0005] The oxidation liquid treatment generally adopts the alkali neutralization method such as lime and carbide slag, such as Chinese patent application CN106277360A, which discloses a method for neutralizing the biological oxidation liquid using alkaline waste residue. This method utilizes the alkaline waste residue produced by the production of acetylene gas in a chemical plant to neutralize the acidic oxidation liquid produced by the biological oxidation operation of the biological oxidation gold extraction plant. This not only solves the pollution caused to the environment by the stacking of alkaline waste residue in the chemical plant, but also solves the pollution caused to the surrounding environment by the discharge of acidic oxidation liquid in the biological oxidation gold extraction plant, achieving zero pollution discharge and achieving the purpose of treating waste with waste. However, there is a problem of large amount of slag produced by neutralization, which increases transportation and storage costs. The cyanide tailings slurry is generally treated separately using the Inco process or hydrogen peroxide oxidation process. Due to the need to add copper sulfate as a catalyst, too many copper ions are introduced into the system, which has a certain adverse effect on production indicators. In addition, due to the large amount of reagents used, the processing cost is greatly increased.

[0006] Therefore, how to develop a method for treating pollutants in the bio-oxidation-carbon leaching process of difficult-to-treat gold concentrate, achieve harmless treatment of bio-oxidation liquid and cyanide tailings slurry, and realize the recovery or recycling of valuable elements is an environmental problem that urgently needs to be solved in the current bio-oxidation process. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the present invention aims to provide a method for treating pollutants in the process of bio-oxidation carbon leaching of gold from refractory gold concentrate.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for treating pollutants in a process for leaching gold from refractory gold concentrate using bio-oxidation carbon comprises the following steps:

[0010] S1. After the bio-oxidation slurry produced by the bio-oxidation of the refractory gold concentrate is thickened, the thickened underflow is subjected to filter pressing and washing; the washed oxidized slag is transferred to step S2, and the thickened overflow, filter press filtrate, and washed liquid are combined to obtain a bio-oxidation liquid, part of which is sent to step S4, and the other part is sent to step S5;

[0011] The reaction processes involved include:

[0012] S x S 2- +CN - →S x-1 S 2- +SCN - Reaction (1)

[0013] fe 3+ +3CN - +3H2O→Fe(OH)3+3HCN Reaction formula (2)

[0014]

[0015] S2. Add water to the oxidized slag to a pulp concentration of 30-40%, add hydrogen peroxide and stir for 1-2 hours. The reaction is shown in (4). Then, add sodium polycyanamide or sodium carbonate cyanurate as an environmentally friendly gold extraction reagent to carry out carbon leaching for 24-30 hours. After leaching is completed, the carbon leaching tail slurry is transferred to step S3 for harmless treatment.

[0016]

[0017] S3, the carbon-leached tailings obtained in step S2 are subjected to filter pressing and washing. After washing, the carbon-leached tailings meet the standards and are discharged into the tailings pond for safe storage. The filter press filtrate is returned to step S2 for slag slurry preparation, and the carbon-leached tailings washing liquid is transferred to step S4 for purification treatment;

[0018] S4. Add iron salt to the washing liquid of carbon leaching tailings, and react for 0.2-1h under stirring. The reaction process is shown in reaction formulas (5) and (6). Then, add the biological oxidation liquid in step S1 and continue to react for 0.2-1h. The reaction process is shown in reaction formula (7). Filter, the total cyanide concentration in the filtrate is less than 10mg / L, and after adjusting the pH value to 6.5-8.5, use microorganisms in landfill leachate sludge or coking plant sludge as thiocyanate degrading bacteria, and add nutrients to adjust the carbon, nitrogen and phosphorus ratio. Under aeration conditions, the thiocyanate in the filtrate is subjected to biological desulfurization treatment. The reaction process is shown in reaction formula (8), so that the concentration of thiocyanate in the filtrate is reduced to below 50mg / L; the filtrate after biological desulfurization is returned to step S3 and recycled for washing water of carbon leaching tailings;

[0019]

[0020]

[0021] S5. The biooxidation liquid is subjected to multi-stage neutralization treatment using flotation tailings. The neutralized slurry is thickened, and the resulting dense underflow is filter-pressed. The filter press residue is sent to the tailings pond for safe storage. The filter press liquid and the dense overflow obtained by thickening the neutralized slurry are combined and sent to step S1 for washing.

[0022] Furthermore, in step S1, the amount of water used for washing is 0.2-1 times the dry weight of the oxidation slag; and in step S5, the number of neutralization stages of the oxidation liquid is 3-6.

[0023] Furthermore, in step S2, the mass concentration of hydrogen peroxide is 30%, the amount added is 0.1-0.5% of the volume of the slurry, and the amount of environmentally friendly gold extraction reagent added is 1-2 times the theoretical amount of sodium cyanide used for gold extraction by cyanide extraction.

[0024] Furthermore, in step S3, the amount of water used for washing the carbon-leached tailings is 0.4-3 times the dry weight of the carbon-leached tailings.

[0025] Furthermore, in step S4, the iron salt is ferrous sulfate heptahydrate, and the mass ratio of the added amount to the environmentally friendly gold extraction reagent in the carbon leaching tailings washing liquid is 5-10, and the iron content in the added biological oxidation liquid is 1-3 times the mass of the environmentally friendly gold extraction reagent in the carbon leaching tailings washing liquid; the biological desulfurization cyanide reaction conditions are water temperature 20-30°C, pH value 6.5-8.5, sludge concentration 3-10g / L, carbon nitrogen phosphorus mass ratio of 100:5:1, dissolved oxygen content 2-6mg / L, and aeration treatment for 24-72h.

[0026] Furthermore, the nutrients include one or more of glucose, ammonium salts, and phosphates.

[0027] Furthermore, in step S5, the flotation tailings are tailings produced by flotation separation of refractory gold ore before biological oxidation.

[0028] The beneficial effects of the present invention are:

[0029] (1) The present invention reduces the amount of impurity ions such as iron, arsenic, and polysulfide entering the carbon-based cyanide leaching process from the source through filter pressing and washing of the biological oxidation slurry, and reduces the amount of pollutants such as ferrocyanide, arsenic, and thiocyanate generated from the source; the biological oxidation slag is oxidized with hydrogen peroxide before carbon-based cyanide leaching to oxidize low-valent sulfur to sulfate ions, thereby reducing the amount of thiocyanate generated from the source and reducing the amount of gold leaching agent used.

[0030] (2) The present invention adopts a low-cyanide agent for carbon-based leaching and cyanidation to reduce the cyanide content in the carbon-based leaching tailings; the carbon-based leaching tailings are subjected to filter pressing and washing, and the filtrate is returned to be used for slurry preparation of the oxide slag and re-enters the cyanidation leaching, thereby making full use of the gold leaching reagent remaining in the filtrate and recovering valuable elements such as gold and silver in the filtrate.

[0031] (3) The present invention uses biological oxidation liquid to treat carbon leaching tailings washing liquid, thereby reducing the cost of cyanide destruction treatment of the carbon leaching tailings washing liquid; the biological oxidation liquid also uses flotation tailings from difficult-to-treat gold mines for neutralization treatment, thereby reducing the amount of neutralization slag produced and the cost of neutralization treatment, and realizing waste treatment with waste.

[0032] (4) The present invention addresses source reduction, process control, and end-of-pipe treatment, achieving the reduction and harmless treatment of pollutants generated during the bio-oxidation and carbon cyanide leaching processes of refractory gold mines. By leveraging the concept of "treating waste with waste," the present invention achieves synergy between pollutant treatment processes, reducing treatment costs and waste residue production while simultaneously recovering a variety of valuable elements, including gold and silver. The present invention has a simple treatment process, low investment and operating costs, and strong application value and prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the method of Examples 1-2 of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0035] Example 1

[0036] This embodiment provides a method for treating pollutants in the process of bio-oxidation carbon leaching of gold from refractory gold concentrate, such as Figure 1 As shown, the following steps are included:

[0037] S1. After the bio-oxidation slurry produced by the bio-oxidation of the refractory gold concentrate is thickened, the thick underflow is filter-pressed, and the oxidation slag obtained by the filter-pressing is washed with water 1 times the dry weight of the oxidation slag; the washed oxidation slag is transferred to step S2, and the thick overflow, the filter press filtrate and the washed liquid are combined to obtain the bio-oxidation liquid, a part of which is sent to step S4, and the other part is sent to step S5.

[0038] S2: Add water to the oxidized slag to a slurry concentration of 30%. 30% hydrogen peroxide is added at 0.5% by volume of the slurry and stirred for 1 hour. Carbonized sodium cyanurate is then added as an environmentally friendly gold extraction reagent and carbonized for leaching for 24 hours. After leaching, the carbonized leached tailings are transferred to step S3 for harmless treatment. The mass of the environmentally friendly gold extraction reagent added is 1.5 times the theoretical amount required for cyanide gold extraction using sodium cyanide.

[0039] S3. The carbon-leached tailings obtained in step S2 are subjected to filter pressing, and the carbon-leached tailings obtained from the filter pressing are washed with water at a volume 0.4 times the dry weight of the carbon-leached tailings. After washing, the carbon-leached tailings meet the tailings pond disposal requirements in the "Technical Specification for Control of Cyanide Residue Pollution in the Gold Industry" (HJ943-2018) and are safely stored in the tailings pond. The filtrate from the carbon-leached tailings filter pressing is returned to step S2 for slag slurry preparation, and the carbon-leached tailings washing liquid is transferred to step S4 for purification. The pollutant composition of the filtrate from the carbon-leached tailings filter pressing is shown in Table 1.

[0040] S4, according to the amount of ferrous sulfate heptahydrate added being 5 times the mass of the environmentally friendly gold extraction reagent in the carbon-leached tailings washing solution, ferrous sulfate heptahydrate was added to the carbon-leached tailings washing solution at 2 g / L, and the reaction was stirred for 0.5 h. Then, according to the iron content in the biological oxidation liquid being 1 times the mass of the gold extraction reagent in the carbon-leached tailings washing solution, the biological oxidation liquid in step S1 was added to the carbon-leached tailings washing solution and the reaction was continued for 0.5 h. After filtering, the total cyanide in the filtrate was 3.2 mg / L, and the thiocyanate concentration was 965 mg / L. After adjusting the pH of the filtrate to 8.5, microorganisms from the coking plant sludge were used as the thiocyanate-degrading bacterial flora, and potassium dihydrogen phosphate was added to adjust the carbon, nitrogen, and phosphorus ratio in the filtrate. The thiocyanate in the filtrate was subjected to biological desulfurization under aeration conditions. The conditions were water temperature of 30°C, pH value of 8.5, coking plant sludge concentration of 3g / L, dissolved oxygen content of 4.5mg / L, potassium dihydrogen phosphate addition of 0.1mg / L, carbon, nitrogen, and phosphorus ratio of 100:5:1 in the filtrate, and aeration treatment time of 24 hours. The thiocyanate concentration dropped to 3.6mg / L. The filtrate after biological desulfurization was returned to step S3 and recycled as washing water for carbon leaching tailings.

[0041] S5. The bio-oxidation liquid is subjected to a three-stage neutralization treatment using the flotation tailings obtained by flotation of the refractory gold ore before bio-oxidation. The neutralized slurry is thickened, and the resulting thick underflow is filter-pressed. The filter press residue is sent to the tailings pond for safe storage. The filter press liquid and the thick overflow obtained by thickening the neutralized slurry are combined and sent to step S1 for washing the oxidation residue.

[0042] Table 1 Pollutant composition of the filtrate of carbon leaching tail slurry filter press mg / L

[0043] Cyanide Thiocyanate As Fe 376 1348 305 212

[0044] Example 2

[0045] This embodiment provides a method for treating pollutants in the process of bio-oxidation carbon leaching of gold from refractory gold concentrate, such as Figure 1 As shown, the following steps are included:

[0046] S1. After the bio-oxidation slurry produced by the bio-oxidation of the refractory gold concentrate is thickened, the thick underflow is filter-pressed, and the oxidation slag obtained by the filter-pressing is washed with water 0.4 times the dry weight of the oxidation slag; the washed oxidation slag is transferred to step S2, and the thickened overflow, the filter press filtrate and the washed liquid are combined to obtain the bio-oxidation liquid, a part of which is sent to step S4, and the other part is sent to step S5.

[0047] In step S2, the oxidized slag is slurried with water to a slurry concentration of 30%. 30% hydrogen peroxide is added at 0.1% by volume of the slurry and stirred for 1 hour. Then, sodium polycyanamide is added as an environmentally friendly gold extraction reagent and carbon-based leaching is carried out for 24 hours. After leaching is completed, the carbon-based leaching tailings are transferred to step S3 for harmless treatment. The amount of environmentally friendly gold extraction reagent added is 1.5 times the theoretical amount required for cyanide gold extraction using sodium cyanide.

[0048] S3. The carbon-leached tailings obtained in step S2 are subjected to filter pressing, and the carbon-leached tailings obtained by the filter pressing are washed with water in an amount 2.5 times the dry weight of the carbon-leached tailings. After washing, the carbon-leached tailings meet the tailings pond disposal requirements in the "Technical Specifications for Control of Cyanide Slag Pollution in the Gold Industry" (HJ943-2018) and are discharged into the tailings pond for safe storage. The filtrate obtained by the filter pressing of the carbon-leached tailings is returned to step S2 for slag slurrying, and the carbon-leached tailings washing liquid is transferred to step S4 for purification treatment.

[0049] S4, according to the amount of iron salt added being 10 times the mass of the gold extraction reagent in the carbon-leached tailings washing solution, ferrous sulfate heptahydrate was added to the carbon-leached tailings washing solution at 4 g / L, and the reaction was stirred for 0.2 h. Then, according to the iron content in the biological oxidation liquid being 3 times the mass of the gold extraction reagent in the carbon-leached tailings washing solution, the biological oxidation liquid in step S1 was added to the carbon-leached tailings washing solution and the reaction was continued for 0.2 h. After filtering, the total cyanide in the filtrate was 4.5 mg / L, and the thiocyanate concentration was 1274 mg / L. After adjusting the pH of the filtrate to 7, the microorganisms in the landfill leachate sludge were used as the thiocyanate-degrading bacterial community. Potassium dihydrogen phosphate was added to adjust the carbon, nitrogen, and phosphorus ratio in the filtrate. The thiocyanate in the filtrate was subjected to biological desulfurization under aeration conditions. The conditions were water temperature of 25°C, pH of 7, sludge concentration of 6g / L, dissolved oxygen content of 3mg / L, potassium dihydrogen phosphate added in an amount of 0.1mg / L, and a carbon, nitrogen, and phosphorus ratio of 100:5:1 in the filtrate. The aeration treatment time was 72 hours, and the thiocyanate concentration dropped to 7.5mg / L. The filtrate after biological desulfurization was returned to step S3 and recycled as washing water for carbon leaching tailings.

[0050] S5. The bio-oxidation liquid is subjected to a six-stage neutralization treatment using flotation tailings obtained by flotation of refractory gold ore before bio-oxidation. The neutralized slurry is thickened, and the resulting dense underflow is filter-pressed. The filter press residue is sent to a tailings pond for safe storage. The filter press liquid and the dense overflow obtained by thickening the neutralized slurry are combined and sent to step S1 for washing.

[0051] Comparative experiment

[0052] The refractory gold concentrate obtained after flotation of a refractory gold ore of a gold mining enterprise was pretreated using a bio-oxidation pretreatment process. After the generated bio-oxidation slurry was concentrated, the concentrated underflow was filter-pressed. A portion of the slag was washed with water 0.4 times the dry weight of the slag, while the other portion was not washed. The compositions of the washed and unwashed slags are shown in Table 2.

[0053] Table 2 Oxidation slag pollutant composition g / kg

[0054] Components As Fe S Unwashed 146.3 584.6 550.8 After washing 7.4 123.5 131.2

[0055] The unwashed slag was slurried with water to a 30% slurry concentration. The slurry was then divided into two groups. One group added 30% hydrogen peroxide at 0.1% of the slurry volume and stirred for 1 hour, while the other group did not add hydrogen peroxide. Both slurries were then cyanided with sodium polycyanamide and subjected to carbon-based leaching under the same conditions. The contaminant composition of the filter press filtrate from the carbon-based leaching tailings is shown in Table 3, and the gold content of the carbon-based leaching tailings obtained after filter pressing and washing is shown in Table 4.

[0056] Table 3 Pollutant composition of filter press filtrate of carbon leaching tail slurry mg / L

[0057] Components Thiocyanate As Fe Not oxidized with hydrogen peroxide 3810 380 820 Hydrogen peroxide oxidation 2635 366 785

[0058] Table 4 Gold content in carbon leaching tailings

[0059] Components Au(g / t) Cost of ton of mineral hydrogen peroxide (yuan) Hydrogen peroxide oxidation 3.16 2 Not oxidized with hydrogen peroxide 3.35 0

[0060] In addition, the ore pulp, which had not been oxidized with hydrogen peroxide, was divided into two groups. One group was treated with sodium polycyanamide for carbonic leaching for 24 hours, while the other group was treated with sodium cyanide. The amount of environmentally friendly gold extraction reagent added was 1.5 times the amount of sodium cyanide. The carbonic leaching tailings and filter press filtrate obtained after filter press washing are shown in Tables 5 and 6.

[0061] Table 5 Gold content in carbon leaching tailings and leaching cost per ton of ore

[0062] Components Au(g / t) Cost of leaching reagents per ton of ore (yuan) Sodium cyanide leaching 3.16 391 Environmentally friendly gold extraction reagents 3.54 399

[0063] Table 6 Pollutant composition of filter press filtrate of carbon leaching tail slurry mg / L

[0064] Components Total cyanide Thiocyanate As Fe Sodium cyanide leaching 1092 3810 380 820 Environmentally friendly gold extraction reagents 305 2365 340 230

[0065] As shown in Table 2, after the biological oxidation slurry is washed with filter press, the contents of arsenic, iron and sulfur in the oxidation slag are significantly reduced. As shown in Tables 3 and 4, after oxidation with hydrogen peroxide, the content of thiocyanate in the filter press filtrate of the carbon-leached tailings produced by cyanidation of the oxidation slag is significantly reduced, and the gold content in the carbon-leached tailings is also reduced. This shows that the biological oxidation slurry is washed with filter press and oxidized with hydrogen peroxide to remove impurities, which can not only reduce the content of pollutants entering the cyanidation link, but also reduce the ineffective consumption caused by the reaction of these impurities with the gold extraction reagent. As shown in Tables 5 and 6, at the same leaching reagent cost, the leaching effect of sodium cyanide and environmentally friendly gold extraction reagent is equivalent. The gold content in the carbon-leached tailings of the environmentally friendly gold extraction reagent is slightly higher, but the contents of cyanide, thiocyanate, arsenic and iron in the carbon-leached tailings produced are reduced to varying degrees, reducing the pressure on subsequent tailings purification treatment.

[0066] Those skilled in the art can make various corresponding changes and modifications based on the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for treating pollutants in a process for leaching gold from refractory gold concentrate using bio-oxidation carbon, characterized in that: The following steps are involved: S1. After the bio-oxidation slurry produced by bio-oxidation of refractory gold concentrate is thickened, the thick underflow is filtered and washed; After washing, the oxidized slag is transferred to step S2, and the thickened overflow, the filter press filtrate and the washed liquid are combined to obtain a biological oxidation liquid. Part of the biological oxidation liquid is sent to step S4, and the other part is sent to step S5; S2, add water to the oxidation slag to adjust the pulp mass concentration to 30-40%, add hydrogen peroxide and stir to react for 1-2 hours, add sodium polycyanamide or carbonized sodium cyanurate as an environmentally friendly gold extraction reagent and carry out carbon leaching for 24-30 hours. After leaching is completed, the carbon leaching tail slurry is transferred to step S3 for harmless treatment; the dosage of the environmentally friendly gold extraction reagent is 1-2 times the mass of sodium cyanide used for theoretical cyanide gold extraction; S3, the carbon-leached tailings obtained in step S2 are subjected to filter pressing and washing. After washing, the carbon-leached tailings meet the standards and are discharged into the tailings pond for safe storage. The filter press filtrate is returned to step S2 for slag slurry preparation, and the carbon-leached tailings washing liquid is transferred to step S4 for purification treatment; S4, adding iron salt to the carbon leaching tailings washing liquid, reacting for 0.2-1h under stirring, then adding the biological oxidation solution in step S1 and continuing the reaction for 0.2-1h, filtering, and adjusting the total cyanide concentration in the filtrate to less than 10mg / L. After adjusting the pH value to 6.5-8.5, using microorganisms in landfill leachate sludge or coking plant sludge as thiocyanate-degrading bacterial flora, adding nutrients to adjust the carbon, nitrogen and phosphorus ratio, and biologically desulfurizing the thiocyanate in the filtrate under aeration conditions to reduce the concentration of thiocyanate in the filtrate to less than 50mg / L; the filtrate after biological desulfurization is returned to step S3 and recycled for washing water of the carbon leaching tailings; S5. The biooxidation liquid is subjected to multi-stage neutralization treatment using flotation tailings. The neutralized slurry is thickened, and the resulting dense underflow is filter-pressed. The filter press residue is sent to the tailings pond for safe storage. The filter press liquid and the dense overflow obtained by thickening the neutralized slurry are combined and sent to step S1 for washing.

2. The processing method according to claim 1, characterized in that In step S5, the number of stages of neutralization of the oxidizing liquid is 3-6.

3. The processing method according to claim 1, characterized in that In step S2, the mass concentration of hydrogen peroxide is 30%, and the amount added is 0.1-0.5% of the volume of the slurry.

4. The processing method according to claim 1, characterized in that In step S4, the iron salt is ferrous sulfate heptahydrate, and the mass ratio of the added amount to the environmentally friendly gold extraction reagent in the carbon leaching tailings washing liquid is 5-10:

1. The iron content in the added biological oxidation liquid is 1-3 times the mass of the environmentally friendly gold extraction reagent in the carbon leaching tailings washing liquid; the biological desulfurization and cyanide reaction conditions are water temperature 20-30°C, pH value 6.5-8.5, sludge concentration 3-10g / L, carbon nitrogen and phosphorus mass ratio of 100:5:1, and aeration treatment for 24-72h.

5. The processing method according to claim 4, characterized in that: The nutrients include one or more of glucose, ammonium salts, and phosphates.

6. The processing method according to claim 1, characterized in that In step S5, the flotation tailings are tailings produced by flotation separation of refractory gold ore before biological oxidation.

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