Method for in-situ electrochemical generation of active oxygen to assist low-cyanide treatment of gold-containing material

Abstract

The application provides a method for electrochemically in-situ generating active oxygen to assist low-cyanide treatment of gold-containing materials, and belongs to the field of gold hydrometallurgy. The method comprises the following steps: crushing gold-containing ores, adding water, protective alkali and sodium cyanide to obtain a slurry, and performing electrochemical assisted leaching on the slurry to obtain a gold-containing leaching solution. The application is based on the fact that there is a 2-electron reduction path in the cathode half-reaction of the cyanide leaching gold process: O2+2H2O+2e→H2O2+2OH ‑ By strengthening the ability of the cathode to produce H2O2 through the application of an external electric field, the oxidation driving force can be achieved in a "self-supply" manner, without relying on the chemical addition of H2O2, so as to maintain the rapid dissolution of gold under low cyanide concentration.

Description

Technical Field

[0001] This application relates to the field of gold hydrometallurgical technology, specifically to a method for electrochemical in-situ generation of active oxygen to assist in the treatment of gold-containing materials with low cyanide. Background Technology

[0002] Cyanide leaching is currently the mainstream process for gold extraction worldwide. Its basic principle is based on the Elsner equation: 4Au + 8CN - + O2 + 2H2O → 4[Au(CN)2] - + 4OH - Dissolved oxygen, acting as the cathode electron acceptor, is a key oxidant for gold dissolution.

[0003] However, cyanide leaching faces two core problems: First, the dissolved oxygen concentration in industrial cyanide systems is usually only 6-10 mg / L, far below the optimal concentration (>15 mg / L) required for rapid gold dissolution, resulting in slow leaching rates and long cycles. Second, to compensate for insufficient dissolved oxygen, industrial processes often increase the cyanide concentration to maintain leaching momentum, resulting in sodium cyanide consumption typically being 0.3-1.5 kg / t of ore. For complex and difficult-to-process ores containing harmful impurities such as copper and arsenic, sodium cyanide consumption can be as high as 3-5 kg / t or even more, not only increasing reagent costs (accounting for 20%-40% of the total cost) but also bringing severe environmental pressure and safety risks.

[0004] In the existing technology, the main methods to increase dissolved oxygen include: (1) pressure swing adsorption (PSA) oxygen generator for on-site oxygen supply (dissolved oxygen can reach 15~30 mg / L), but the equipment investment is large and the operating cost is high; (2) adding H2O2 as a chemical oxidant, which can accelerate leaching, but H2O2 is chemically unstable, difficult to transport and store, and excessive addition will cause CN to be added. - Oxidized to CNO - (CN) - + H2O2→CNO - (+ H2O), which increases cyanide consumption; (3) High-shear pre-oxidation reactors (such as Aachen reactors) improve oxygen mass transfer efficiency through physical means, but still rely on external oxygen supply.

[0005] In conclusion, developing a method for treating gold-containing materials with low cyanide levels assisted by active oxygen is an urgent need in the field of gold hydrometallurgy. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a method for electrochemical in-situ generation of active oxygen to assist in the treatment of gold-containing materials with low cyanide. This method can achieve "self-supplied" oxidation driving force, without relying on the chemical addition of H2O2, and can maintain the rapid dissolution of gold at low cyanide concentrations.

[0007] To achieve the above objectives, embodiments of this application provide a method for electrochemical in-situ generation of active oxygen to assist in the treatment of gold-containing materials with low cyanide, comprising the following steps: S1. Crush the gold-bearing ore and add water to prepare the first slurry; S2. Add protective alkali to the first slurry and adjust the pH to obtain the second slurry; S3. Add sodium cyanide to the second slurry to obtain the third slurry; S4. In the leaching reactor, the third slurry is subjected to electrochemical-assisted leaching to obtain a gold-containing leachate; The leaching reactor is equipped with a carbon-based gas diffusion cathode and an inert anode, with an insulating membrane between the cathode and the anode. During the electrochemical assisted leaching, oxygen-containing gas is introduced into the cathode side and a DC power supply is connected.

[0008] Furthermore, in step S4, when performing the electrochemical assisted leaching, a constant potential mode or a square wave pulse current mode is adopted; the electrochemical assisted leaching time is 24~48h.

[0009] Furthermore, in step S4, when the constant potential mode is used, the cathode potential is controlled to be -0.3V to -1.0V, and the current density is 5 to 50 mA / cm². 2 .

[0010] Furthermore, in step S4, when using the square wave pulse current mode, the pulse frequency is controlled to be 0.1~10Hz, the duty cycle to be 20%~80%, and the peak current density to be 20~100 mA / cm². 2 .

[0011] Furthermore, in step S4, the electrochemical assisted leaching process also includes a swirling enhancement step: applying a swirling field to the third slurry, with the swirling intensity measured by the inlet flow rate, having an intensity of 1.0~5.0 m / s.

[0012] Furthermore, in step S4, the carbon-based gas diffusion cathode is one or more of carbon felt, graphite felt, carbon cloth, and modified carbon paper; the inert anode is one of DSA electrode, platinum-titanium electrode, and stainless steel electrode; and the insulating diaphragm is one of porous polyethylene diaphragm, polypropylene diaphragm, or ceramic membrane with a pore size of 0.1~10μm.

[0013] Furthermore, in step S4, the oxygen-containing gas is one or a mixture of air and pure oxygen, the ventilation rate of the oxygen-containing gas is 0.5~2.0 L / min, and the concentration of dissolved oxygen in the third slurry is ≥10 mg / L.

[0014] Furthermore, in step S1, after the gold ore is crushed, the mass percentage of particles with a particle size of less than 200 mesh is ≥85%.

[0015] Furthermore, in step S2, the pH of the second slurry is 10.0~11.5.

[0016] Furthermore, in step S3, the concentration of free cyanide ions in the third slurry is 50~200 mg / L.

[0017] The beneficial technical effects of this application are as follows: (1) In this invention, oxygen-containing gas is introduced into the cathode side during electrochemical assisted leaching of the ore slurry. The electrochemically generated H2O2 directly replenishes the oxidant required for the cathode half-reaction, accelerating the anodic dissolution kinetics of gold. The leaching rate is increased by 20% to 40% compared with the traditional process, and the leaching time is shortened. H2O2 is generated and consumed in situ on the electrode surface, eliminating the need for external H2O2 transportation, storage and addition, thus eliminating the safety hazards of H2O2 storage and transportation.

[0018] (2) This invention provides oxidation driving force by electrochemical in-situ production of active oxygen (ROS), which can reduce the concentration of free cyanide from the traditional 300~500 mg / L to 50~200 mg / L, and reduce the amount of sodium cyanide used by 50%~70%. The significant reduction in the amount of cyanide used directly reduces the amount of cyanide residue in the tail liquid, thereby reducing the cost and environmental risks of subsequent cyanide destruction treatment.

[0019] (3) Precise and controllable concentration of reactive oxygen species (ROS): By adjusting the current density and cathode potential, the yield and concentration of H2O2 can be precisely controlled and always maintained in the optimal range for "promoting leaching", avoiding the negative effects of excessively high local concentrations when chemically adding H2O2 on CN. - Side reactions of oxidative decomposition.

[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. Detailed Implementation

[0021] The following embodiments are only used to illustrate the technical solutions of this application more clearly, and are therefore only examples and should not be used to limit the scope of protection of this application.

[0022] 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 and claims of this application are intended to cover non-exclusive inclusion.

[0023] 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 in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0024] 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 indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0025] Currently, there is no technical solution that combines electrochemical in-situ generation of reactive oxygen species (ROS) with a low-concentration cyanide leaching system.

[0026] To address the aforementioned technical problems, this application provides a method for electrochemical in-situ generation of active oxygen to assist in the treatment of gold-containing materials with low-cyanide compounds, comprising the following steps: S1. Crush the gold-bearing ore and add water to prepare the first slurry; S2. Add protective alkali to the first slurry and adjust the pH to obtain the second slurry; S3. Add sodium cyanide to the second slurry to obtain the third slurry; S4. Electrochemical assisted leaching of the third slurry is carried out in the leaching reactor to obtain a gold-containing leachate. The leaching reactor is equipped with a carbon-based gas diffusion cathode and an inert anode, with an insulating membrane between the cathode and the anode. During electrochemical assisted leaching, oxygen-containing gas is introduced to the cathode side and a DC power supply is connected.

[0027] In the technical solution of this application, the cathode half-reaction of the cyanide leaching gold process has a 2-electron reduction pathway: O2 + 2H2O + 2e → H2O2 + 2OH- - During electrochemical assisted leaching, oxygen-containing gas is introduced into the side where the carbon-based gas diffusion cathode is located, and a DC power supply is connected. By utilizing the external electric field and the gas-liquid-solid three-phase interface of the cathode material to enhance the cathode's ability to produce H2O2, a "self-supplied" oxidation driving force can be achieved without relying on the chemical addition of H2O2, thereby maintaining the rapid dissolution of gold at low cyanide concentrations.

[0028] In some embodiments, during step S4, electrochemical assisted leaching is performed in a constant potential mode or a square wave pulse current mode; the electrochemical assisted leaching time is 24~48h.

[0029] In this embodiment, the use of pulse mode can avoid excessive accumulation of H2O2 on the cathode surface and improve the utilization efficiency of ROS; by controlling the time of electrochemical assisted leaching, sufficient reaction time of ROS is ensured, thereby increasing the gold content of the gold-containing leaching solution.

[0030] In some embodiments, in step S4, when the constant potential mode is adopted, the cathode potential is controlled to be -0.3V to -1.0V, and the current density is 5 to 50 mA / cm². 2 .

[0031] In this embodiment, by precisely adjusting the ROS yield through controlling the current density and cathode potential, it can be maintained within the concentration range that "appropriately promotes leaching," thus avoiding excessive ROS leading to CN. - Side reactions of oxidative decomposition. Preferably, the cathode potential is -0.5V to -0.8V, and the current density is 10 to 30 mA / cm². 2 Under these conditions, the in-situ yield of H2O2 is 5~30 mg / (L·h).

[0032] It should be noted that the cathode potentials in this application are all relative to the saturated calomel electrode (SCE).

[0033] In some embodiments, in step S4, when the square wave pulse current mode is used, the pulse frequency is controlled to be 0.1~10 Hz, the duty cycle to be 20%~80%, and the peak current density to be 20~100 mA / cm². 2 .

[0034] In this embodiment, by controlling the pulse frequency and peak current density of the square wave pulse current, the yield and concentration of H2O2 are precisely controlled, always maintaining it within the optimal range for "promoting leaching," thus avoiding the negative effects on CN due to excessively high local concentrations when chemically adding H2O2. - Side reactions of oxidative decomposition.

[0035] In some embodiments, during electrochemical assisted leaching in step S4, a swirl enhancement step is further included: applying a swirl field to the third slurry, wherein the swirl intensity is measured in terms of inlet flow velocity and is 1.0~5.0 m / s.

[0036] In this embodiment, the thickness of the diffusion layer on the cathode surface is reduced by the swirling shear force of the swirling flow field, thereby enhancing the mass transfer rate of O2 to the cathode surface and increasing the yield of H2O2.

[0037] In some embodiments, in step S4, the carbon-based gas diffusion cathode is one or more of carbon felt, graphite felt, carbon cloth, and modified carbon paper; the inert anode is one of DSA electrode, platinum-titanium electrode, and stainless steel electrode; and the insulating diaphragm is one of porous polyethylene diaphragm, polypropylene diaphragm, or ceramic membrane with a pore size of 0.1~10μm.

[0038] In this embodiment, the surface of the carbon-based gas diffusion cathode is hydrophobically treated to form a gas-liquid-solid three-phase interface, which can promote the 2-electron reduction reaction of O2 on the cathode surface (O2 + 2H2O + 2e → H2O2 + 2OH-). - The inert anode acts only as a medium for electron transfer during electrolysis and does not participate in the chemical reaction itself, thus avoiding contamination of the gold-containing leaching solution; the insulating diaphragm has a pore size of 0.1~10μm, allowing OH- - CN - Na + Small ions can pass through freely, but mineral slurry particles with a diameter >10μm are retained to prevent the electrode surface from being contaminated and passivated by mineral slurry solids.

[0039] It can be noted that the DSA electrode is an inert anode based on titanium coated with ruthenium oxide and iridium oxide (RuO2 / IrO2).

[0040] In some embodiments, in step S4, the oxygen-containing gas is one or a mixture of air and pure oxygen, the ventilation rate of the oxygen-containing gas is 0.5~2.0 L / min, and the concentration of dissolved oxygen in the third slurry is ≥10 mg / L.

[0041] In this embodiment, dissolved oxygen acts as the cathode electron acceptor and is a key oxidant for gold dissolution. Introducing oxygen-containing gas further increases the concentration of dissolved oxygen, thereby promoting gold dissolution.

[0042] In some embodiments, in step S1, after the gold ore is crushed, the mass percentage of particles with a particle size of less than 200 mesh is ≥85%.

[0043] In this embodiment, by crushing the gold-bearing ore to a particle size of less than 200 mesh, the mineral monomers are liberated, creating the necessary conditions for subsequent processes.

[0044] In some embodiments, in step S2, the pH of the second slurry is 10.0 to 11.5.

[0045] In this embodiment, the pH of the slurry is adjusted to 10.0~11.5 to prevent the generation of highly toxic hydrogen cyanide (HCN) gas and ensure the safe and effective operation of the process.

[0046] In some embodiments, in step S3, the concentration of free cyanide in the third slurry is 50~200 mg / L.

[0047] In this embodiment, the concentration of free cyanide can be reduced from 300-500 mg / L in the traditional process to 50-200 mg / L, and the amount of sodium cyanide used can be reduced by 50%-70%, which directly reduces the amount of cyanide residue in the tail liquid and reduces the cost and environmental risks of subsequent cyanide destruction treatment.

[0048] The embodiments of this application will be described in further detail below with reference to the examples. The detailed description of the following embodiments is used to illustrate the principles of this application, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0049] I. Preparation Method Example 1 This embodiment provides a method for treating gold-bearing materials by electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment. The method mainly utilizes an electrochemical-assisted low-cyanide system to leach oxidized gold ore. The specific steps are as follows: A sample of oxidized gold ore was taken from a gold mine. The gold grade of the sample was 1.46 g / t, and the main gangues were quartz and limonite, with a small amount of pyrite (S 0.8%). The sample was ball-milled until 90% of the sample was smaller than 200 mesh, and water was added to prepare a slurry with a mass concentration of 33%.

[0050] Lime slurry was added to the slurry to adjust the pH to 10.5. A carbon felt (effective area 200 cm²) was installed as a carbon-based gas diffusion cathode in a 5L laboratory leaching reactor. 2 The cathode consists of a DSA electrode serving as the inert anode and a porous PE membrane with a pore size of 1 μm wrapped around the outside. Pure oxygen is introduced into the cathode at a flow rate of 0.5 L / min.

[0051] Adding NaCN to the slurry controls the free CN content. - The concentration was 100 mg / L. A potentiostat was connected, and the cathode potential was controlled at -0.65V (vs. SCE), corresponding to a current density of approximately 20 mA / cm². 2 Electrochemical assisted leaching for 24 hours.

[0052] Example 2 This embodiment provides a method for electrochemical in-situ generation of active oxygen to assist in the treatment of gold-bearing materials with low-cyanide leaching. It mainly utilizes a swirling electric field to enhance the leaching of sulfide-containing gold ore with low-cyanide leaching. The specific steps are as follows: A sample of an arsenic-sulfide gold ore was taken. The gold grade of the ore sample was 6.83 g / t, containing 3.5% pyrite and 1.2% arsenopyrite (As 1.8%, S 4.2%). The ore sample was ball-milled until 85% of the fraction was smaller than 200 mesh, and water was added to prepare a slurry with a mass concentration of 30%.

[0053] First, a pre-oxidation treatment is carried out: air is introduced into the slurry, the slurry pH is 10.5, and the mixture is stirred and pre-oxidized for 4 hours to partially oxidize and passivate the active sites on the surface of pyrite and arsenopyrite, thereby reducing the activity of cyanide-consuming impurities in the subsequent cyanidation stage.

[0054] After pre-oxidation, adjust the pH to 10.8 and add NaCN to control free CN. - The concentration was 120 mg / L. A graphite felt cathode (effective area 500 cm²) was installed as a carbon-based gas diffusion cathode in a cyclone-electrochemical coupled reactor. 2 The reactor contains a DSA electrode that acts as an inert anode. The slurry enters the reactor tangentially at an inlet velocity of 2.5 m / s, forming a swirling flow field.

[0055] Pure oxygen is introduced to the cathode side, and a potentiostat is connected to control the cathode potential at -0.7V (vs. SCE), with a current density of 25 mA / cm². 2 Electrochemical treatment for 36 hours.

[0056] Example 3 This embodiment provides a method for electrochemical in-situ generation of active oxygen to assist in the treatment of gold-bearing materials with low-cyanide compounds. It mainly utilizes a pulsed electrochemical mode to assist in the low-cyanide leaching of highly muddy oxidized gold ore. The specific steps are as follows: A sample of a highly muddy oxidized gold ore was taken. The gold grade of the ore sample was 3.21 g / t, and the mud content was 15%. The ore sample was ball-milled until the fraction smaller than 200 mesh accounted for 88% of the sample. Water was added to prepare a slurry with a mass concentration of 28%. Polyacrylamide (10 g / t) was added to improve the settling performance of the slurry.

[0057] Adjust the pH to 10.3 and add NaCN to control free CN. - The concentration was 80 mg / L. A modified carbon paper cathode as the carbon-based gas diffusion cathode and a DSA electrode as the inert anode were installed in a 5L leaching reactor. A square wave pulse power supply was used, with the following parameters: pulse frequency 1 Hz, duty cycle 50%, and peak current density 50 mA / cm². 2 (Average current density 25 mA / cm²) 2 Air was introduced to the cathode side, and pulsed electrochemical assisted leaching was performed for 48 hours.

[0058] Example 4 This embodiment provides a method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials. It mainly utilizes electrochemically assisted low-cyanide leaching acid pretreatment of PCB electronic slag containing gold. The specific steps are as follows: XRF analysis of PCB (printed circuit board) incineration residue from a certain electronic waste showed a gold content of 12.8 g / t, with the main components being SiO2 (32%), Al2O3 (11%), Fe2O3 (20%), CuO (17%), and SnO2 (6%). The gold primarily exists as fine inclusions within the metal oxide matrix.

[0059] First, acid pretreatment was performed: PCB slag was leached with a 1.5 mol / L H2SO4 + 3% H2O2 solution at 70°C with stirring for 12 hours to dissolve most of the base metal impurities such as copper, tin, and lead (Cu leaching rate > 92%). After filtration, the acid-treated residue was obtained. The acid-treated residue was washed three times with deionized water until the pH of the effluent was > 6, and then dried for later use.

[0060] The acid-treated PCB slag residue was mixed with water to prepare a slurry with a mass concentration of 30%. Lime slurry was added to the slurry to adjust the pH to 10.8.

[0061] A graphite felt gas diffusion cathode (effective area 300 cm²) was installed in a 5L laboratory leaching reactor. 2 The cathode is equipped with a titanium-based DSA anode and a porous PE membrane with a pore size of 1 μm. Pure oxygen is introduced into the cathode side at a flow rate of 0.8 L / min.

[0062] Adding NaCN to the slurry controls the free CN content. - The concentration was 150 mg / L. A potentiostat was connected, and the cathode potential was controlled at -0.7V (vs. SCE), corresponding to a current density of approximately 22 mA / cm². 2 Electrochemical assisted leaching for 36 hours.

[0063] Comparative Example 1 This comparative example provides a method for processing gold-bearing materials, mainly employing a conventional cyanidation method to leach the same oxide gold ore as in Example 1. The difference from Example 1 is that NaCN controls the free CN content. - The concentration was 400 mg / L (typical concentration for conventional processes), and mechanical stirring (200 rpm) was used for 24 hours without introducing pure oxygen, adding H2O2, or applying an electric field. Other steps and experimental parameters were basically the same as in Example 1, and will not be repeated here.

[0064] Comparative Example 2 This comparative example provides a method for processing gold-bearing materials, mainly employing conventional cyanidation leaching to extract sulfide-containing gold ore similar to that in Example 2. The difference from Example 2 is that NaCN controls the free CN content. -The concentration was 500 mg / L (typical concentration for conventional processes), and mechanical stirring (200 rpm) was used for 48 hours. No pretreatment, no additional pure oxygen was introduced, no H2O2 was added, and no electric field was applied. Other steps and experimental parameters were basically the same as in Example 2, and will not be repeated here.

[0065] Comparative Example 3 This comparative example provides a method for processing gold-bearing materials, mainly employing a conventional cyanidation method to leach the same oxide gold ore as in Example 3. The difference from Example 3 is that NaCN controls the free CN content. - The concentration was 350 mg / L (typical concentration for conventional processes), and mechanical stirring (200 rpm) was used for 48 hours without introducing pure oxygen, adding H2O2, or applying an electric field. Other steps and experimental parameters were basically the same as in Example 3, and will not be repeated here.

[0066] Comparative Example 4 This comparative example provides a method for treating gold-containing materials. It primarily employs a conventional cyanidation method to leach the same PCB electronic waste gold-containing material as in Example 4. The difference from Example 4 is that NaCN controls the free CN content. - The concentration was 400 mg / L (typical concentration for conventional processes), and mechanical stirring (200 rpm) was used for 48 hours without introducing pure oxygen, adding H2O2, or applying an electric field. Other steps and experimental parameters were basically the same as in Example 4, and will not be repeated here.

[0067] Comparative Example 5 This comparative example provides a method for treating gold-bearing materials, mainly exploring the effect of exogenous H2O2 addition on the cyanidation system. This comparative example uses the same gold oxide ore as Example 1, but differs in that a 30% (w / w) H2O2 solution is directly added to the slurry, controlling the H2O2 concentration at 50 mg / L, and free CN... - The concentration was 100 mg / L. Other steps and experimental parameters were basically the same as in Example 1, and will not be repeated here.

[0068] Comparative Example 6 This comparative example provides a method for processing gold-bearing materials, mainly employing a conventional cyanidation method to leach the same oxide gold ore as in Example 1. The difference from Example 1 is that NaCN controls the free CN content. - The concentration was 400 mg / L (typical concentration for conventional processes), and mechanical stirring (200 rpm) was used for 24 hours without introducing pure oxygen, adding H2O2, or applying an electric field. Other steps and experimental parameters were basically the same as in Example 1, and will not be repeated here.

[0069] Examples 5-8 and Comparative Examples 7-8 Examples 5-8 and Comparative Examples 7-8 respectively provide a method for treating gold-bearing materials by electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment. This method mainly utilizes an electrochemical-assisted + low-cyanide system to leach oxidized gold ore. The difference from Example 1 lies in the cathode potential and current density; specific parameters are shown in Table 1. Other steps and experimental parameters are basically the same as in Example 1 and will not be repeated here.

[0070] Table 1. Cathode potential and current density in Examples 5-8 and Comparative Examples 7-8 II. Analysis Results The gold-containing leachates of Examples 1-8 and Comparative Examples 1-8 were sampled and analyzed, and the results are shown in Table 2.

[0071] Table 2. Sampling analysis results of Examples 1-8 and Comparative Examples 1-8 Comparing Example 1 and Comparative Example 1, it can be seen that the gold leaching rate of the electrochemical-assisted + low-cyanide system increased by 1.7 percentage points under the condition that the sodium cyanide dosage was reduced by 47.5%.

[0072] Comparing Example 2 and Comparative Example 2, it can be seen that the pre-oxidation + swirling electric field assisted + low-cyanide system increased the gold leaching rate by 7.4 percentage points under the condition of reducing sodium cyanide dosage by 59.6%. The swirling field maintained the dissolved oxygen concentration above 25 mg / L, and the cathode H2O2 yield increased by about 35% compared with the static conditions.

[0073] Comparing Example 3 and Comparative Example 3, it can be seen that the gold leaching rate increased by 3.3 percentage points in the pulsed electrochemical-assisted + low-cyanide system under the condition of a 49.6% reduction in sodium cyanide dosage. The advantage of the pulsed mode is that intermittent oxygen supply avoids excessive accumulation and ineffective decomposition of H2O2 on the cathode surface.

[0074] Although acid treatment in Comparative Example 4 removed most of the base metals, residual Cu and Fe continued to consume cyanide to form copper-cyanide and iron-cyanide complexes, resulting in persistently high cyanide consumption. Comparing Example 4 and Comparative Example 4, it can be seen that the acid pretreatment + electrochemical assistance + low-cyanide system, with a 22% reduction in sodium cyanide dosage, increased the gold leaching rate by 23.2 percentage points compared to the traditional process. Electrochemical in-situ ROS production not only provided sufficient oxidation driving force but also oxidized residual Cu through the oxidation of H2O2. + Oxidized to Cu 2+ Reduce the impact of copper cyanide complexes on CN - This eliminates ineffective consumption and achieves the dual effect of "oxidative enhancement + cyanide reduction".

[0075] In Comparative Example 5, the initial leaching rate of H2O2 was rapid, but after 2 hours, the H2O2 was almost completely decomposed (catalytic decomposition of Fe minerals in the ore), and CNO was detected. - The increased concentration indicates that some CN - Oxidized to CNO - The actual cyanide consumption was higher than that of the electrochemical in-situ ROS production scheme. A comparison of Example 1 and Comparative Example 5 shows that the addition of exogenous H2O2 exhibits a "high initially, low later" concentration problem; initial excess leads to increased CN content. - Decomposition and insufficient subsequent oxidation-driving force lead to a lack of oxidation. Electrochemical in-situ ROS production can maintain the H2O2 concentration within the optimal range, which is the core advantage of this invention.

[0076] A comparison of Example 1 and Comparative Example 6 reveals that, under conventional cyanidation conditions relying solely on air agitation, dissolved oxygen levels remain consistently low (7-8 mg / L). The gold dissolution rate is limited by the cathode oxygen reduction step, and even with an extended leaching time of 48 hours, the leaching rate is still significantly lower than that of the electrochemically assisted method. This clearly demonstrates that insufficient dissolved oxygen supply is the core bottleneck restricting cyanidation leaching efficiency, and also confirms the necessity of this invention to enhance oxidation supply through electrochemical in-situ ROS production.

[0077] The above comparison results show that the concentration of reactive oxygen species generated in situ through electrochemical processes is related to the cathode potential, The current density is closely related. At a cathode potential of -0.3V to -1.0V (vs. SCE), the current density is 5~50 mA / cm². 2 High gold leaching rates can be obtained within the specified range. However, excessively negative potentials (above -1.0V, such as -1.2V in Comparative Example 7) exacerbate hydrogen evolution side reactions, reduce the selectivity of oxygen reduction to produce H2O2, resulting in insufficient active oxygen supply, sodium cyanide consumption increasing to 1.23 kg / t, and the gold leaching rate decreasing to 85.8%. When the potential is insufficient (such as -0.1V in Comparative Example 8), the cathode has difficulty initiating the O2 reduction reaction, the in-situ H2O2 is almost zero, and the gold leaching rate drops to 83.3%. Therefore, only by limiting the cathode potential and current density within the range of this invention can a sufficient and stable in-situ active oxygen supply be guaranteed while avoiding the consumption of cyanide ions by side reactions, thus achieving the synergistic effect of "low cyanide + high leaching".

[0078] 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. Various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing embodiments by combining some of the constituent elements, are also included in the scope of this application without departing from the spirit of this application.

Claims

1. A method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials, characterized in that, Includes the following steps: S1. Crush the gold-bearing ore and add water to prepare the first slurry; S2. Add protective alkali to the first slurry and adjust the pH to obtain the second slurry; S3. Add sodium cyanide to the second slurry to obtain the third slurry; S4. In the leaching reactor, the third slurry is subjected to electrochemical-assisted leaching to obtain a gold-containing leachate; The leaching reactor is equipped with a carbon-based gas diffusion cathode and an inert anode, with an insulating membrane between the cathode and the anode. During the electrochemical assisted leaching, oxygen-containing gas is introduced into the cathode side and a DC power supply is connected.

2. The method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials according to claim 1, characterized in that, In step S4, the electrochemical assisted leaching is performed using a constant potential mode or a square wave pulse current mode; the electrochemical assisted leaching time is 24~48h.

3. The method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials according to claim 2, characterized in that, In step S4, when the constant potential mode is used, the cathode potential is controlled to be -0.3V to -1.0V, and the current density is 5 to 50 mA / cm². 2 .

4. The method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials according to claim 2, characterized in that, In step S4, when using the square wave pulse current mode, the pulse frequency is controlled to be 0.1~10 Hz, the duty cycle to be 20%~80%, and the peak current density to be 20~100 mA / cm². 2 .

5. The method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials according to claim 1, characterized in that, In step S4, the electrochemical assisted leaching process further includes a swirling enhancement step: applying a swirling field to the third slurry, with the swirling intensity measured by the inlet flow rate and having an intensity of 1.0~5.0 m / s.

6. The method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials according to claim 1, characterized in that, In step S4, the carbon-based gas diffusion cathode is one or more of carbon felt, graphite felt, carbon cloth, and modified carbon paper; the inert anode is one of DSA electrode, platinum-titanium electrode, and stainless steel electrode; and the insulating diaphragm is one of porous polyethylene diaphragm, polypropylene diaphragm, or ceramic membrane with a pore size of 0.1~10μm.

7. The method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials according to claim 1, characterized in that, In step S4, the oxygen-containing gas is one or a mixture of air and pure oxygen, the ventilation rate of the oxygen-containing gas is 0.5~2.0 L / min, and the concentration of dissolved oxygen in the third slurry is ≥10 mg / L.

8. The method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials according to claim 1, characterized in that, In step S1, after the gold ore is crushed, the mass percentage of particles with a particle size of less than 200 mesh is ≥85%.

9. The method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials according to claim 1, characterized in that, In step S2, the pH of the second slurry is 10.0~11.

5.

10. The method for electrochemical in-situ generation of active oxygen-assisted low-cyanide treatment of gold-containing materials according to claim 1, characterized in that, In step S3, the concentration of free cyanide in the third slurry is 50~200 mg / L.

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