Leaching aids and leaching processes for cyanide leaching

Abstract

The application provides a kind of cyanide leaching of immersion aid and leaching method, belongs to cyanide leaching gold field, wherein, the immersion aid is composed of the following mass percentage components: ammonium persulfate 50~80%, potassium citrate 10~30%, calcium peroxide 5~10%, ergothioneine 5~10%. The immersion aid provided by the application is added to the cyanide leaching process, which can improve the leaching efficiency, shorten the leaching time and reduce the amount of sodium cyanide. Compared with traditional immersion aid, the formula does not contain heavy metals, reduces the risk of environmental pollution, and the combination of ammonium persulfate and calcium peroxide is more stable than single oxidizing agent and is not easy to decompose and fail. The immersion aid has the advantages of oxidation strengthening, impurity inhibition and environmental friendliness, and can be widely used in cyanide gold extraction process, and has significant industrial application value.

Description

Technical Field

[0001] This invention relates to the field of cyanide leaching technology, specifically to a leaching aid and leaching method for cyanide leaching. Background Technology

[0002] Cyanide leaching is a core technology for extracting precious metals such as gold and silver from ores. The leaching process utilizes the reaction of cyanide (such as sodium cyanide) with gold minerals to form soluble gold-cyanide complexes, thereby separating and recovering the gold. However, for certain specific ores, cyanide leaching suffers from slow leaching rates and high cyanide consumption, impacting production efficiency and economic benefits.

[0003] A leaching aid is a chemical additive used to improve the efficiency of cyanide leaching. It enhances dissolution capacity, promotes the reaction between metal ions and cyanide, inhibits interference from harmful ions, and shortens the leaching cycle. Currently commonly used leaching aids, such as lead nitrate and hydrogen peroxide, have drawbacks such as heavy metal pollution or chemical instability and easy decomposition, which limit their use.

[0004] In view of this, it is necessary to design a leaching aid and leaching method for cyanide leaching to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a cyanide leaching aid and leaching method, which aims to solve the technical problems of heavy metal pollution or chemical instability and easy decomposition of existing cyanide leaching aids. By designing a new leaching aid, the gold leaching rate is accelerated while reducing the amount of cyanide and reducing the introduction of new harmful substances.

[0006] In a first aspect, this application provides a cyanide leaching aid, which is composed of the following components in mass percentage: 50-80% ammonium persulfate, 10-30% potassium citrate, 5-10% calcium peroxide, and 5-10% ergothioneine.

[0007] Secondly, this application provides a cyanide leaching method using the leaching aid described in the first aspect, comprising the following steps:

[0008] S1. Grind the gold-bearing ore to a -0.074mm content of 80~95%, and adjust the mass concentration of the slurry to the predetermined range;

[0009] S2. Add protective alkali to treat the slurry with alkali;

[0010] S3. Add leaching aid and sodium cyanide to the slurry simultaneously, stir and leach to obtain cyanide leaching solution.

[0011] As a further improvement of this application, in step S1, the mass concentration of the slurry is 25-40%.

[0012] As a further improvement of this application, in step S2, the protective alkali is calcium oxide or calcium hydroxide, and the pH value of the slurry is adjusted to 9.5~11.

[0013] As a further improvement of this application, the alkali treatment time is 1 to 3 hours.

[0014] As a further improvement of this application, in step S3, the amount of the immersion aid is 0.5~5 kg / t; the amount of sodium cyanide is 0.8~8 kg / t.

[0015] As a further improvement of this application, the stirring leaching time is 4~48h.

[0016] As a further improvement to this application, the gold-bearing ore is a copper-bearing gold ore, and the copper content in the ore is 0.1~0.5%.

[0017] The beneficial effects of this application are as follows:

[0018] This application provides a leaching aid for cyanide leaching and a leaching method. The leaching aid is composed of the following components by mass percentage: 50-80% ammonium persulfate, 10-30% potassium citrate, 5-10% calcium peroxide, and 5-10% ergothioneine. Adding this leaching aid to the cyanide leaching process can improve leaching efficiency, shorten leaching time, and reduce the amount of sodium cyanide used. Compared to traditional leaching aids (such as lead nitrate), this formulation does not contain heavy metals, reducing the risk of environmental pollution. Furthermore, the combination of ammonium persulfate and calcium peroxide is more stable than a single oxidant (such as H₂O₂) and less prone to decomposition and degradation. This leaching aid is suitable for refractory copper-gold ores, significantly shortening the leaching cycle and improving the recovery rate of precious metals.

[0019] Ammonium persulfate, as a strong oxidizing agent, can effectively destroy the passivation layer on the mineral surface and promote the cyanide dissolution of gold. Calcium peroxide slowly releases oxygen, maintaining a high dissolved oxygen environment in the leaching system and accelerating the cyanide reaction. Potassium citrate stabilizes interfering ions such as copper and iron in the solution through chelation, reducing their ineffective consumption of cyanide. Ergot thiourea, due to its antioxidant and metal complexing abilities, can inhibit harmful side reactions and improve cyanide utilization. This leaching aid combines the advantages of oxidation enhancement, impurity inhibition, and environmental friendliness, and can be widely used in cyanide gold extraction processes, demonstrating significant industrial application value.

[0020] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0022] Figure 1 This is a flowchart of the cyanide leaching method provided in the embodiments of this application. Detailed Implementation

[0023] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0025] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0028] Cyanide leaching processes suffer from slow leaching rates and high cyanide consumption for certain ores, impacting production efficiency and economic benefits. Currently used cyanide leaching aids, such as lead nitrate and hydrogen peroxide, have drawbacks such as heavy metal contamination or chemical instability and easy decomposition, limiting their application.

[0029] To address the technical problems of heavy metal pollution or chemical instability and easy decomposition of existing cyanide leaching aids, this application provides a cyanide leaching aid and leaching method. By designing the composition and ratio of the aid, it is possible to accelerate the gold leaching rate while reducing the amount of cyanide used and reducing the introduction of new harmful substances.

[0030] In a first aspect, embodiments of this application provide a cyanide leaching aid, which is composed of the following components by mass percentage: 50-80% ammonium persulfate, 10-30% potassium citrate, 5-10% calcium peroxide, and 5-10% ergothioneine.

[0031] In this leaching aid formulation, ammonium persulfate ((NH4)2S2O8) acts as a strong oxidizing agent, first oxidizing metallic copper to Cu. 2+ It forms a stable [Cu(NH3)4] in the ammonia water system. 2+ A complex that activates S2O8 through coordination. 2- This triggers homolytic cleavage to generate highly reactive sulfate radicals (SO4). - The oxidation process involving free radicals will reduce gold (Au) to gold. 0 The gold is gradually oxidized to Au(I) and Au(III), while sodium cyanide (NaCN) stabilizes the high-valence gold through coordination, forming soluble [Au(CN)2]. - In this process, Cu 2+ Reduced to Cu + Ergothioneine, with its unique thiourea-imidazolium structure, selectively chelates Cu. + This forms a stable [Cu(ergothioneine)] + Complex, effectively inhibits Cu + The disproportionation or precipitation of S2O8 in the system reduces its redox potential, making it more susceptible to disproportionation or precipitation by excess S2O8 in the system. 2- Re-oxidized to Cu 2+ This enables the regeneration of the Cu(II) / Cu(I) oxidation cycle. This multi-level synergistic mechanism constructs a self-sustaining catalytic oxidation closed-loop system through free radical transport, metal valence state conversion, and ligand dynamic regulation, significantly improving the oxidation and dissolution efficiency of gold.

[0032] The core mechanism by which the leaching aid provided in this application reduces the amount of sodium cyanide (NaCN) lies in reducing dependence on cyanide ions by strengthening the free radical-mediated oxidation pathway and optimizing the metal complexation balance. (S2O8) 2- In the copper-ammonia complex ([Cu(NH3)4) 2+ Sulfate radicals (SO4) generated by homolytic cleavage under catalysis- ·) Direct gold oxide (Au) 0 The reaction path of gold from zero oxidation state to soluble state is shortened by moving it to a higher oxidation state (Au(I) / Au(III)), thereby reducing the cyanide (CN) ion concentration. - This is solely for the consumption of stabilizing ligands. Meanwhile, ergothioneine's response to Cu... + The efficient chelation inhibited its disproportionation (2Cu) + → Cu 2+ + Cu 0 ) or with CN - Competitive binding (such as the formation of CuCN) maintains the continuity of the Cu(I) / Cu(II) cycle, allowing a limited number of cyanide ions to preferentially and directionally complex with high-value gold (forming [Au(CN)2)). - SO42- (not consumed by side reactions) - The strong oxidizing properties of cyanide may partially replace its oxidizing function, directly achieving the oxidative dissolution of gold through a multi-electron transfer mechanism, further reducing the system's absolute dependence on cyanide. This synergistic mechanism minimizes the amount of cyanide used through radical-dominated oxidation, precise control of metal valence state, and ligand selective competition.

[0033] Calcium peroxide (CaO2) and potassium citrate (K3C6H5O7) are introduced to synergistically regulate the redox potential and metal ion coordination environment, thus optimizing the reaction pathway. Under alkaline conditions, calcium peroxide gradually releases H2O2 and O2, and its decomposition products (such as hydroxyl radicals ·OH) react with persulfate radicals (SO42-). - • A complementary oxidation network is formed, increasing the overall oxidation potential of the system and promoting the efficient oxidation and dissolution of gold. Simultaneously, H₂O₂, as a mild oxidant, can selectively regenerate Cu(I) to Cu(II), inhibiting Cu… + This reduces ineffective dissipation and enhances the efficiency of the Cu(II) / Cu(I) cycle. Sodium citrate, on the other hand, dynamically complexes free Cu through its carboxylic acid groups. 2+ This reduces its effective concentration and alleviates the effects of the copper-ammonia complex ([Cu(NH3)4)). 2+ Excessive dissociation of [Cu(NH3)4] helps maintain the stability of the catalytic active site; its buffering effect also regulates the pH of the system, inhibiting the ineffective decomposition of H2O2 and the precipitation of metal hydroxides. Furthermore, the competitive coordination between citrate and ammonia can fine-tune [Cu(NH3)4]. 2+ The coordination field strength is optimized to enhance its effect on S2O8. 2- The activation capacity of the active ingredient, combined with the potential regulation function of H2O2, forms a potential control mechanism with multi-level oxidant synergy and precise metal coordination balance, thereby improving the oxidation kinetics of the system while reducing sodium cyanide dependence. The four components work synergistically through multiple mechanisms such as oxidation, complexation, buffering, and stabilization to significantly improve the efficiency of cyanide leaching of gold, while reducing cyanide consumption and environmental pollution risks.

[0034] Please refer to Figure 1 Secondly, embodiments of this application provide a cyanide leaching method using the leaching aid described in the first aspect, comprising the following steps:

[0035] S1. Grind the gold-bearing ore to a -0.074mm content of 80~95%, and adjust the mass concentration of the slurry to the predetermined range;

[0036] S2. Add protective alkali to treat the slurry with alkali;

[0037] S3. Add leaching aid and sodium cyanide to the slurry simultaneously, stir and leach to obtain cyanide leaching solution.

[0038] This cyanide leaching method utilizes the aforementioned leaching aids (ammonium persulfate, potassium citrate, calcium peroxide, and ergothioneine). By optimizing key steps such as grinding, alkali treatment, and synergistic leaching, the dissolution rate and recovery rate of gold are improved. Grinding to -0.074 mm (200 mesh) with 80-95% particle size can effectively disrupt the mineral structure, allowing for complete dissociation of gold particles and increasing the contact area with cyanide. Grinding too coarsely will prevent the gold from being released, while grinding too finely may increase slime and affect subsequent solid-liquid separation. Sodium cyanide (NaCN) generates highly toxic HCN gas under acidic conditions; adding a protective alkali inhibits HCN formation, and a high pH environment can reduce CN. - The cyanide is oxidized to a useless cyanate, improving the effective utilization rate of cyanide; the addition of a leaching aid and sodium cyanide avoids the waste of oxidant caused by stepwise addition, as adding ammonium persulfate alone may over-oxidize CN. - Stirring during leaching promotes oxygen diffusion, enhances gold dissolution kinetics, prevents slurry sedimentation, and ensures full contact between the reagent and gold particles.

[0039] Furthermore, in some embodiments, the mass concentration of the slurry is 25-40%.

[0040] In the technical solution of this application embodiment, the slurry concentration ensures the fluidity of the slurry, facilitates stirring and oxygen diffusion, and too high a concentration will reduce mass transfer efficiency, while too low a concentration will increase reagent consumption.

[0041] Furthermore, in some embodiments, the protective alkali is calcium oxide or calcium hydroxide, and the pH of the slurry is adjusted to 9.5-11. The alkali treatment time is 1-3 hours.

[0042] In the technical solution of this application embodiment, the protective alkali is a strongly alkaline substance that can rapidly increase the pH of the slurry, inhibit the formation of HCN, and ensure operational safety; if pH < 9.5, CN - It readily converts to HCN, reducing the effective cyanide concentration and decreasing dissolved oxygen utilization. If pH > 11, OH... -Excessive alkaline treatment can inhibit gold dissolution and accelerate cyanide hydrolysis. Too short an alkaline treatment time may lead to incomplete reaction, pH fluctuations, or insufficient impurity removal; too long a time will reduce processing capacity and increase energy consumption.

[0043] Furthermore, in some embodiments, the amount of the immersion aid is 0.5~5 kg / t; the amount of sodium cyanide is 0.8~8 kg / t.

[0044] In the technical solution of this application embodiment, the leaching aid is mainly used to improve the dissolution efficiency of gold in cyanide leaching, and its dosage needs to be adjusted according to the ore properties (such as sulfide content and gold encapsulation ratio); sodium cyanide is the core leaching agent, and its dosage is closely related to the ore grade and mineral composition; the ratio of leaching aid to sodium cyanide needs to be balanced. Excessive leaching aid may lead to an increase in slurry viscosity, which is not conducive to diffusion, and excessive sodium cyanide will increase costs and environmental pressure.

[0045] Furthermore, in some embodiments, the stirring leaching time is 4 to 48 hours.

[0046] In the technical solution of this application embodiment, the stirring leaching time ensures complete leaching and achieves a high recovery rate.

[0047] Furthermore, in some embodiments, the gold-bearing ore is a copper-bearing gold ore, with a copper content of 0.1-0.5%.

[0048] In the technical solution of this application embodiment, for copper-containing gold ore, the leaching aid provided by this application can accelerate the gold leaching rate while reducing the amount of cyanide and reducing the introduction of new harmful substances.

[0049] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0050] Example 1

[0051] This embodiment provides a cyanide leaching method for a gold-bearing ore with a gold grade of 1.05 g / t, copper content of 0.14%, and silicon dioxide content of 65.17%. Figure 1 As shown, the specific steps include:

[0052] S1. Grind the gold-bearing ore to -0.074mm with a content of 80% using a ball mill, and then prepare it into a slurry with a concentration of 40%.

[0053] S2. Add calcium oxide to adjust the pH of the slurry to 10.5, and treat with alkali for 2 hours;

[0054] S3. Add 0.8 kg / t of leaching aid and 1.0 kg / t of sodium cyanide to the alkali-treated slurry, stir and leach for 16 hours, and obtain cyanide leaching solution after solid-liquid separation. The leaching aid consists of the following components by mass percentage: ammonium persulfate 80%, potassium citrate 10%, calcium peroxide 5%, and ergothioneine 5%.

[0055] The conventional cyanide leaching method uses 1.8 kg / t of sodium cyanide and a stirring leaching time of 24 h, resulting in a gold leaching rate of 90.48%. After using the leaching aid provided in this application, the amount of sodium cyanide used is reduced by 44.44%, the leaching time is reduced by 8 h, and the gold leaching rate is 95.24%, an increase of 4.76%.

[0056] Example 2

[0057] This embodiment provides a cyanide leaching method for a gold-bearing ore with a gold grade of 1.91 g / t, a copper content of 0.35%, and a silica content of 70.98%, and includes the following steps:

[0058] S1. Grind the gold-bearing ore to -0.074mm with a content of 90% using a ball mill, and then prepare it into a slurry with a concentration of 40%.

[0059] S2. Add calcium oxide to adjust the pH of the slurry to 10.5, and treat with alkali for 2 hours;

[0060] S3. Add 1.5 kg / t of leaching aid and 0.8 kg / t of sodium cyanide to the alkali-treated slurry, stir and leach for 24 hours, and obtain cyanide leaching solution after solid-liquid separation. The leaching aid consists of the following components by mass percentage: ammonium persulfate 50%, potassium citrate 30%, calcium peroxide 10%, and ergothioneine 10%.

[0061] The conventional cyanide leaching method uses 2.0 kg / t of sodium cyanide and a stirring leaching time of 30 h, resulting in a gold leaching rate of 87.96%. After using the leaching aid provided in this application, the amount of sodium cyanide used is reduced by 60.00%, the leaching time is reduced by 6 h, and the gold leaching rate is 92.15%, an increase of 4.19%.

[0062] Comparative Example 1

[0063] Comparative Example 1 provides a cyanide leaching method. The only difference from Example 1 is that ammonium persulfate is not introduced into the leaching aid system. Specifically, the system consists of 0% ammonium persulfate, 50% potassium citrate, 25% calcium peroxide, and 25% ergothioneine. Other experimental parameters and conditions are basically the same as in Example 1 and will not be repeated here.

[0064] In conventional cyanide leaching, the sodium cyanide dosage was 1.8 kg / t, the stirring leaching time was 24 h, and the gold leaching rate was 90.48%. When the leaching aid from Comparative Example 1 was added, under the same conditions of sodium cyanide dosage and leaching time as in Example 1, the gold leaching rate was still 90.48%, and the leaching aid effect was not significant.

[0065] Comparative Example 2

[0066] Comparative Example 2 provides a cyanide leaching method. The only difference from Example 2 is that potassium citrate is not introduced into the leaching aid system. Specifically, the system consists of 89.0% ammonium persulfate, 0% potassium citrate, 5.5% calcium peroxide, and 5.5% ergothioneine. Other experimental parameters and conditions are basically the same as in Example 2 and will not be repeated here.

[0067] In conventional cyanide leaching, the sodium cyanide dosage is 2.0 kg / t, the stirring leaching time is 30 h, and the gold leaching rate is 87.96%. Under the sodium cyanide and leaching time conditions in Example 2, the gold leaching rate after using the leaching aid in Comparative Example 2 is 81.67%, which is 6.29% lower than that of conventional cyanide leaching. The leaching aid did not improve the gold leaching index.

[0068] Comparative Example 3

[0069] Comparative Example 3 provides a cyanide leaching method. The only difference from Example 2 is that calcium peroxide is not introduced into the leaching aid system. Specifically, the system consists of 84.2% ammonium persulfate, 10.5% potassium citrate, 0% calcium peroxide, and 5.3% ergothioneine. Other experimental parameters and conditions are basically the same as in Example 2 and will not be repeated here.

[0070] In conventional cyanide leaching, the sodium cyanide dosage was 2.0 kg / t, the stirring leaching time was 30 h, and the gold leaching rate was 87.96%. After using the leaching aid in Comparative Example 3, the gold leaching rate was 86.39%, which was 1.57% lower than that of conventional cyanide leaching. The leaching aid had little effect on the sodium cyanide dosage.

[0071] Comparative Example 4

[0072] Comparative Example 4 provides a cyanide leaching method. Compared with Example 1, the only difference is that ergothioneine is not introduced into the leaching aid system. Specifically, the system consists of 84.2% ammonium persulfate, 10.5% potassium citrate, 5.3% calcium peroxide, and 0% ergothioneine. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be repeated here.

[0073] In conventional cyanide leaching, the sodium cyanide dosage was 1.8 kg / t, the stirring leaching time was 24 h, and the gold leaching rate was 90.48%. With the addition of the leaching aid in Comparative Example 4, under the same conditions as in Example 1, the gold leaching rate was 88.57%, and the leaching aid did not significantly improve the leaching rate.

[0074] Table 1. Cyanide leaching results of examples and comparative examples.

[0075]

[0076] Table 1 shows that the synergistic effect of the components in the leaching aid constructs a multi-level oxidation-coordination dynamic equilibrium system, which is achieved through free radical relay oxidation (SO4). - The efficient leaching of gold is achieved through a triple coupling mechanism involving complementary activation of · / ·OH groups, metal valence state cycling (efficient regeneration of Cu(II) / Cu(I) under the regulation of ergothioneine and calcium peroxide), and ligand competition regulation (selective complexation of ammonia / citrate / cyanide). Persulfate and calcium peroxide synergistically broaden the oxidation potential window, directly driving the stepwise oxidation of gold and reducing dependence on cyanide oxidation. Ergothioneine and sodium citrate respectively leach gold through Cu… + Chelation and Cu 2+ The buffering and stabilizing effect of sodium cyanide on the copper catalytic center prevents cyanide from being consumed by side reactions. Simultaneously, sodium cyanide is used only as a stabilizing ligand for high-valent gold, rather than as the primary oxidant, and its dosage is precisely controlled to the complexation requirement threshold. This synergistic optimization of the closed-loop self-sustaining oxidation network and the coordination microenvironment ultimately achieves the goal of efficient gold leaching and low cyanide consumption.

[0077] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A leaching aid for cyanide leaching, characterized in that, The immersion aid is composed of the following components by mass percentage: 50-80% ammonium persulfate, 10-30% potassium citrate, 5-10% calcium peroxide, and 5-10% ergothioneine.

2. A cyanide leaching method, using the leaching aid as described in claim 1, characterized in that, Includes the following steps: S1. Grind the gold-bearing ore to a -0.074mm content of 80~95%, and adjust the mass concentration of the slurry to the predetermined range; S2. Add protective alkali to treat the slurry with alkali; S3. Add leaching aid and sodium cyanide to the slurry simultaneously, stir and leach to obtain cyanide leaching solution.

3. The cyanide leaching method according to claim 2, characterized in that, In step S1, the mass concentration of the slurry is 25-40%.

4. The cyanide leaching method according to claim 2, characterized in that, In step S2, the protective alkali is calcium oxide or calcium hydroxide, and the pH of the slurry is adjusted to 9.5-11.

5. The cyanide leaching method according to claim 4, characterized in that, The alkali treatment time is 1 to 3 hours.

6. The cyanide leaching method according to claim 2, characterized in that, In step S3, the amount of the immersion aid is 0.5~5 kg / t; the amount of sodium cyanide is 0.8~8 kg / t.

7. The cyanide leaching method according to claim 6, characterized in that, The stirring and leaching time is 4 to 48 hours.

8. The cyanide leaching method according to claim 2, characterized in that, The gold-bearing ore is a copper-bearing gold ore, with a copper content of 0.1-0.5%.

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