Method for extracting gold from electronic waste based on cyanide-free gold leaching agent system based on endogenous bromine recycling

Abstract

This application provides a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on the recycling of endogenous bromine, which belongs to the field of precious metal recycling technology. This method constructs a compound free radical initiator-ammonium chloride cyanide-free gold leaching agent system, utilizes bromine-containing flame retardant materials in electronic waste and ammonium chloride to construct an autocatalytic reaction system, significantly increasing the steady-state concentration of bromine free radicals, thereby enhancing the oxidation ability of gold, and directly oxidizing gold to generate Au. 3+ ; Cl in the pre-introduced ammonium chloride ‑ With Au 3+ Instant complexation to form [AuCl4] ‑ , achieving gold leaching, while NH4 + It forms a copper-ammine complex ([Cu(NH3)4] 2+ ), the complex will deactivate Br in a free radical environment ‑ It is reactivated to Br·, forming a complete closed-loop cycle of bromine radical oxidation-gold dissolution-bromine ion regeneration. This self-sustaining reaction mechanism not only stabilizes bromine radical concentration at an optimal level but also achieves a gold leaching rate of ≥98% under mild conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of precious metal recycling, and in particular to a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on the cyclic regeneration of endogenous bromine. Background Art

[0002] Currently, gold extraction from e-waste primarily relies on cyanide, but cyanide is highly toxic and poses safety risks. While cyanide-free technologies (such as the thiosulfate method and the glycine method) can mitigate environmental risks, the complex metal composition of e-waste makes it difficult to achieve highly selective gold leaching, resulting in low recovery rates and hindering large-scale application.

[0003] Currently, the field of gold extraction from electronic waste faces technical bottlenecks, necessitating the development of efficient, environmentally friendly, cyanide-free gold extraction technologies that overcome the limitations of traditional cyanide processes. The development of new, green gold extraction reagents and processes will not only significantly increase precious metal recovery rates but also completely eliminate the environmental and safety risks posed by cyanide, providing key technical support for the sustainable development of the gold industry.

[0004] Through innovative cyanide-free gold extraction technology, we can achieve efficient recycling of solid waste resources such as electronic waste, enhancing the independent and controllable supply chain capabilities of key metals. This breakthrough not only aligns with the country's green development goals, but also promotes the upgrading of the circular economy industry, providing important support for resource security and the development of an ecological civilization. Summary of the Invention

[0005] In response to the key bottleneck problems of poor selectivity and low efficiency of current cyanide-free gold leaching agents in treating electronic waste, this application provides a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling.

[0006] This method utilizes bromine-containing flame retardants already present in electronic waste and ammonium chloride to create an autocatalytic reaction system. This sustainable bromine source, combined with an external free radical initiator, creates a synergistic effect, boosting gold oxidation efficiency by an order of magnitude. This self-sustaining reaction mechanism not only stabilizes bromine radical concentrations at an optimal level but also achieves a gold leaching rate of ≥98% under mild conditions (pH 1-4, room temperature). Furthermore, the wastewater can be recycled, fundamentally addressing the key scientific challenges of traditional cyanide-free processes, such as high reagent consumption and low efficiency.

[0007] The present application provides a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on the recycling of endogenous bromine, comprising the following steps:

[0008] S1, grinding the electronic waste to obtain a pulp, and adjusting the pH value of the pulp to a predetermined pH; the electronic waste contains bromine and copper;

[0009] S2, mixing a compounded free radical initiator with ammonium chloride to obtain a cyanide-free gold leaching agent system; wherein the compounded free radical initiator is a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride) and potassium peroxymonosulfate, or a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and sodium persulfate;

[0010] S3, adding the cyanide-free gold leaching agent system to the ore pulp, stirring, and obtaining a precious gold solution and a solid residue.

[0011] Among them, the gold content in the solid residue is tested by fire assay method, and the test and analysis method refers to "GB / T7739".

[0012] The gold leaching situation can be judged based on the gold leaching rate.

[0013]

[0014] Wherein, η represents the leaching rate of gold, in units of %; m1 represents the mass of the original material, in units of g; β1 represents the grade of the original material, in units of g / t; m2 represents the mass of the solid residue after leaching, in units of g; β2 represents the grade of the solid residue after leaching, in units of g / t.

[0015] The gold-containing precious liquid was tested by ICP-OES, and the gold leaching rate was auxiliary proved according to the gold concentration in the gold-containing precious liquid. The error of the two methods was less than 1%, indicating that the data obtained by this method was valid data.

[0016] Furthermore, the bromine element is derived from flame retardant materials in electronic waste.

[0017] Furthermore, in the cyanide-free gold leaching agent system, the mass ratio of the 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride), potassium permonosulfate and ammonium chloride is 1:(1-4):(5-20).

[0018] Furthermore, in the cyanide-free gold leaching agent system, the mass ratio of the 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride), sodium persulfate and ammonium chloride is 1:(1-4):(5-20).

[0019] Furthermore, in step S3, the stirring reaction time is at least 1 hour.

[0020] Furthermore, the predetermined pH is 1-4.

[0021] Furthermore, the electronic waste includes at least one of discarded circuit boards, integrated chips, and discarded electrode materials.

[0022] Furthermore, during the grinding treatment, the electronic waste is ground to a particle size of less than 100 mesh, and the content of the particle size accounts for 90%-98% of the total mass of the mineral powder.

[0023] Furthermore, the mass concentration of the slurry is 1%-10%.

[0024] Furthermore, the pH value of the slurry is adjusted by adding a pH adjuster; the pH adjuster is hydrochloric acid.

[0025] The beneficial effects of this application are:

[0026] 1. This application proposes a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on the recycling of endogenous bromine. The cyanide-free gold leaching agent system is a compounded free radical initiator-ammonium chloride system. The core of this method is to simultaneously utilize the bromine-containing flame retardant material in the electronic waste and the added ammonium chloride to construct an autocatalytic reaction system. In an acidic medium (pH 1-4), the flame retardant material is stimulated to dissociate by a compounded free radical initiator (VA-044 / PMS compound or VA-044 / sodium persulfate compound) to generate bromine radicals (Br·). First, the free radical initiator A (PMS or sodium persulfate) decomposes to produce sulfate radicals (·SO4 - ), this strong oxidizing free radical can efficiently capture the bromine atoms in the brominated flame retardant to generate Br·; at the same time, the free radical initiator B (VA-044) decomposes under the same conditions to produce carbon-centered free radicals (·R), which can not only directly activate the C-Br bond, but also react with the bromide ions (Br - ) undergoes an electron transfer reaction and reoxidizes it to Br·, forming a "double radical relay activation" mechanism.

[0027] In addition, the protons (H + ) maintains the acidic environment of the reaction system, which not only promotes the decomposition efficiency of the free radical initiator B, but also inhibits the volatilization loss of bromine species.

[0028] This synergistic effect increases the steady-state concentration of bromine radicals by more than 3 times, thereby significantly enhancing its ability to oxidize precious metals (such as gold) and directly oxidize gold to generate Au. 3+ At the same time, the Cl in the pre-introduced ammonium chloride - With Au 3+ Instant complexation to form [AuCl4] - To achieve gold leaching, NH4 + It forms a copper-ammine complex ([Cu(NH3)4] 2+ ), the complex will deactivate Br in a free radical environment -It is reactivated to Br·, forming a complete closed cycle of "bromine radical oxidation-gold dissolution-bromine ion regeneration".

[0029] 2. In this application, bromine-containing flame retardants from electronic waste serve as a sustainable bromine source, creating a synergistic effect with an external free radical initiator, increasing gold oxidation efficiency by an order of magnitude. This self-sustaining reaction mechanism not only stabilizes bromine radical concentrations at an optimal level but also achieves a gold leaching rate of ≥98% under mild conditions (pH 1-4, room temperature). The wastewater can also be recycled, fundamentally addressing the key scientific issues of high reagent consumption and low efficiency in traditional cyanide-free processes. Through the precise coupling of multiple chemical processes, this system provides an efficient, economical, and environmentally friendly solution for the resource recovery of electronic waste.

[0030] 3. This invention, through the innovative construction of a bromine free radical recycling catalytic system, achieves an optimal balance between economic and environmental benefits while ensuring technical feasibility. This provides a new, economically feasible and environmentally friendly approach to electronic waste resource utilization, effectively resolving the industry's challenge of balancing technical performance with economic and environmental benefits in traditional cyanide-free processes.

[0031] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0033] Figure 1 These are the results of mineral phase dissociation analysis of electronic waste.

[0034] Figure 2 It is the storage form of gold in electronic waste.

[0035] Figure 3 The occurrence forms of copper in electronic waste; (a) is a photo of the copper-containing sample before and after cutting; (b) is a backscattered photo of the sample; (c) is the element surface distribution of the sample; and (d) is the element energy spectrum analysis diagram of the sample. DETAILED DESCRIPTION

[0036] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0038] The present invention provides a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on the recycling of endogenous bromine, comprising the following steps:

[0039] S1, grinding the electronic waste to obtain a slurry of a preset concentration, and adjusting the pH value of the slurry to a predetermined pH;

[0040] Among them, electronic waste includes at least one of discarded circuit boards, integrated chips, and discarded electrode materials.

[0041] Electronic waste contains bromine and copper elements;

[0042] The bromine element comes from flame retardant materials in electronic waste.

[0043] The composition of copper elements in electronic waste includes pure copper, copper-tin alloy, copper-zinc alloy and copper-nickel alloy.

[0044] Pure copper comes from the copper clad laminate substrate.

[0045] Copper-tin alloys are used in connector spring contacts and lead-free solders.

[0046] Copper-zinc alloys are used in terminal blocks, heat sinks, and decorative coatings.

[0047] Copper-nickel alloys are used in electroplated corrosion protection layers (such as interface plating) and precision resistor components.

[0048] During the grinding process, the electronic waste is ground to a particle size of less than 100 mesh, and the content accounts for 90%-98% of the total mass of the mineral powder.

[0049] Water is added to the electronic waste powder and stirred to obtain a slurry with a mass concentration of 1%-10%. Then, hydrochloric acid, a pH adjuster, is added to adjust the pH of the slurry to 1-4.

[0050] S2, mixing the compounded free radical initiator with ammonium chloride to obtain a cyanide-free gold leaching agent system;

[0051] The compounded free radical initiator is a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride) (VA-044) and potassium peroxymonosulfate (PMS), or a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) and sodium persulfate.

[0052] In the cyanide-free gold leaching agent system, the mass ratio of VA-044, PMS and ammonium chloride is 1: (1-4): (5-20).

[0053] In the cyanide-free gold leaching agent system, the mass ratio of VA-044, sodium persulfate and ammonium chloride is 1: (1-4): (5-20).

[0054] S3, adding a cyanide-free gold leaching agent system to the ore pulp, stirring and reacting for 1-4 hours to obtain a gold-containing precious liquid and a solid residue.

[0055] Among them, the gold content in the solid residue is tested by fire assay method, and the test and analysis method refers to "GB / T7739".

[0056] Calculate the gold leaching rate and determine the gold leaching situation.

[0057]

[0058] Wherein, η represents the leaching rate of gold, in units of %; m1 represents the mass of the original material, in units of g; β1 represents the grade of the original material, in units of g / t; m2 represents the mass of the solid residue after leaching, in units of g; β2 represents the grade of the solid residue after leaching, in units of g / t.

[0059] The gold-containing precious liquid was tested by ICP-OES, and the gold leaching rate was auxiliary proved according to the gold concentration in the gold-containing precious liquid. The error of the two methods was less than 1%, indicating that the data obtained by this method was valid data.

[0060] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0061] Example 1

[0062] Waste circuit boards (a type of electronic waste) containing precious metal resources were selected. The main components of the waste circuit boards are shown in Table 1. The unit is g / t.

[0063] Table 1 Main components of waste circuit boards

[0064]

[0065] *Indicates the unit used is g / t 电子废弃物原料 .

[0066] This embodiment provides a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on the recycling of endogenous bromine, comprising the following steps:

[0067] S1, grinding the electronic waste into a mineral powder with a particle size of less than 100 mesh, accounting for 92%, to obtain a small particle material; adding 50g of electronic waste mineral powder to 1L of water and stirring, the slurry concentration is 5%, and adding hydrochloric acid to adjust the slurry to a pH of 1.

[0068] The results of mineral phase dissociation analysis in electronic waste are as follows: Figure 1 As shown, it can be seen that electronic waste contains copper, bromine and gold elements.

[0069] Among them, the occurrence forms of gold and copper are as follows Figure 2 、 Figure 3 shown.

[0070] S2, mixing the compounded free radical initiator with ammonium chloride to obtain a cyanide-free gold leaching agent system; wherein the compounded free radical initiator is a compound solution of VA-044 and PMS; specifically, 0.5g VA-044, 2g PMS, and 5g ammonium chloride, that is, the mass ratio of VA-044, PMS, and ammonium chloride is 1:4:10.

[0071] S3, adding a cyanide-free gold leaching agent system to the slurry, stirring and reacting for 1 hour to obtain a gold-containing precious liquid and a solid residue.

[0072] Among them, the gold content in the solid residue is tested by fire assay method, and the test and analysis method refers to "GB / T7739".

[0073] Calculate the gold leaching rate and determine the gold leaching situation.

[0074]

[0075] Wherein, η represents the leaching rate of gold, in units of %; m1 represents the mass of the original material, in units of g; β1 represents the grade of the original material, in units of g / t; m2 represents the mass of the solid residue after leaching, in units of g; β2 represents the grade of the solid residue after leaching, in units of g / t.

[0076] The gold-containing precious liquid was tested by ICP-OES, and the gold leaching rate obtained by the method of the present application was auxiliary proved based on the gold concentration in the gold-containing precious liquid. It can be seen that the error between the two methods is less than 1%, indicating that the test value of this method is valid data.

[0077] Example 2

[0078] Example 2 provides a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling. Compared with Example 1, the difference lies in the use of a different type of composite free radical initiator, as shown in Table 2. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0079] Table 2 Types of compound free radical initiators and leaching rates of gold and copper in Examples 1-2

[0080]

[0081] As shown in Table 2, in Examples 1-2, efficient gold leaching (up to 98%) can be achieved. The synergistic oxidation-catalysis mechanism of the compound free radical initiator is as follows: in an acidic medium, potassium peroxymonosulfate (PMS) or sodium persulfate first decomposes to produce strong oxidizing free radicals (·SO4 - ), directly oxidizes the brominated flame retardants in electronic waste to generate bromine radicals (Br·), which then attack gold to form Au 3+ At the same time, the carbon-centered free radical (·R) generated by the decomposition of the water-soluble azo initiator VA-044 not only assists in activating the C-Br bond, but also converts the reaction by-product Br - Reconverted to Br·, forming a bromine radical regeneration network. Although, copper ammonia complex ([Cu(NH3)4] 2+ ) dissociates dynamically under acidic conditions, but the dissociated Cu 2+ With NH4 + Still participates in Br through rapid coordination equilibrium - Catalytic oxidation of NH4 + The local slightly alkaline environment provided delays the complete decomposition of the complex. This synergistic effect of "double radical triggering-copper ammonia dynamic catalysis" not only ensures the continuous supply of bromine radicals, but also through Cl - (from NH4Cl) and Au 3+ The efficient complexation realizes the stable dissolution of gold and finally achieves complete leaching of gold under cyanide-free conditions.

[0082] Examples 3-4 and Comparative Examples 1-2

[0083] Examples 3-4 and Comparative Examples 1-2 provide a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling. Compared with Example 1, the difference is that in step S1, the slurry concentration is different, as shown in Table 3. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0084] Table 3 Slurry concentration and gold and copper leaching rates of Examples 3-4 and Comparative Examples 1-2

[0085]

[0086] As shown in Table 3, slurry concentration has a significant impact on gold leaching efficiency. When the slurry concentration increases from 10% (Example 4) to 15% (Comparative Example 2), the gold leaching rate decreases significantly from 96% to 72%, while the copper leaching rate remains high at 93%.

[0087] This phenomenon reveals three key mechanisms: first, high slurry concentration leads to an increase in the solid content per unit volume, but the dosage of reagents is not increased accordingly, resulting in insufficient effective concentrations of free radical initiators and ammonium chloride, which cannot meet the kinetic requirements of the gold oxidation-complexation reaction; second, the preferential formation of copper ammonia complexes further inhibits gold leaching under reagent-limited conditions; third, experiments have confirmed that the process can maintain a gold leaching rate of more than 96% within a slurry concentration range of 1-10%, providing a clear concentration control window for industrial applications and ensuring leaching efficiency and economic benefits.

[0088] Examples 5-12 and Comparative Examples 3-8

[0089] Examples 5-12 and Comparative Examples 3-8 provide a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on the recycling of endogenous bromine. Compared with Example 1, the difference is that the dosage ratio of each component in the cyanide-free gold leaching agent system is different, as shown in Table 4. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0090] Table 4 The dosage ratio of each component and the gold leaching rate of Examples 5-12 and Comparative Examples 3-8

[0091]

[0092] It can be seen from Table 4 that the reagent composition ratio is the key factor affecting the gold leaching efficiency.

[0093] When the mass ratio of VA-044, PMS, and ammonium chloride is within the range of 1:(1-4):(5-20) (Examples 1-12), the gold leaching rate can be maintained at a high level of 96%-99%, indicating that this ratio range can fully meet the stoichiometric requirements of bromine radical generation, gold oxidation, and complex dissolution.

[0094] Notably, increasing the ammonium chloride:VA-044 mass ratio from 5:1 to 10:1 further increased the leaching rate from 98% to 99%, confirming the importance of sufficient ammonium chloride in maintaining the equilibrium of gold complex dissolution. In contrast, excessively high VA-044 ratios (Comparative Examples 3-5) or low ammonium chloride ratios (Comparative Examples 6-8) resulted in significantly lower leaching rates (49%-92%), demonstrating the necessity of the synergistic effect of the three reagent components.

[0095] The optimal ratio of 1:(1-4):(5-20) not only ensures efficient recycling of bromine radicals but also provides ample gold complexation sites, resulting in stable and efficient gold leaching. These results provide a scientific basis for precise control of reagent ratios in industrial applications.

[0096] Examples 13-15 and Comparative Examples 9-11

[0097] Examples 13-15 and Comparative Examples 9-11 provide a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling and regeneration. Compared with Example 1, the difference is that the pH value of the slurry is different, as shown in Table 5. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0098] Table 5 pH value of slurry and gold leaching rate in Examples 13-15 and Comparative Examples 9-11

[0099]

[0100] — represents the value below the detection limit of ICP-OES. Taking into account the detection error, the gold leaching rate is close to 0.

[0101] As shown in Table 5, in the acidic range of pH 1-4, the gold leaching rate can be maintained at an excellent level of 96%-98%. This is mainly due to the acidic environment's inhibition of the generation of bromine free radicals (PMS decomposes into SO4 - ) and gold complex dissolution ([AuCl4] - However, when the pH was raised to 5, the leaching rate dropped significantly to 87%, and dropped sharply to 35% at pH 6. Under weak alkaline conditions (pH = 8), the leaching reaction was almost completely terminated.

[0102] This phenomenon is primarily attributed to: first, the reduced efficiency of PMS decomposition under neutral to alkaline conditions, resulting in insufficient bromine radical generation; second, increased pH promotes the dissociation of the copper-ammonia complex, disrupting the catalytic regeneration cycle of bromide ions; and third, the significant decrease in the stability of the gold complex with increasing pH. These findings provide a clear process control window (pH 1-4) for industrial applications and emphasize the critical role of maintaining an acidic environment in this technology.

[0103] Examples 16-18 and Comparative Examples 12-13

[0104] Examples 16-18 and Comparative Examples 12-13 provide a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling and regeneration. Compared with Example 1, the difference is that the stirring reaction time is different, as shown in Table 6. The other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0105] Table 6 Stirring reaction time and gold leaching rate of Examples 16-18 and Comparative Examples 12-13

[0106]

[0107] As can be seen from Table 6, the influence of stirring time on gold leaching efficiency is as follows: when the reaction time is increased from 0.5 hours (Comparative Example 12) to 1 hour (Example 1), the gold leaching rate significantly increases from 86% to 98%, indicating that 1 hour is the critical time node for the reaction to reach basic equilibrium; when the stirring time is further extended to 2-5 hours (Examples 16-18 and Comparative Example 13), the leaching rate remains in a stable range of 98-99%, confirming that the reaction system has reached completion after 4 hours.

[0108] This phenomenon indicates that: 1) the generation of bromine radicals and the gold complex dissolution require at least 1 hour to complete the primary reaction process; 2) a stirring time that is too short (0.5 hours) results in incomplete oxidation-complexation reactions, while a stirring time that is too long (>4 hours) does not increase the marginal benefit (99% to 100%). Therefore, controlling the stirring time to 1-4 hours maximizes leaching efficiency while avoiding wasted energy and time.

[0109] In summary, the present invention provides a method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on the recycling of endogenous bromine. This method achieves green, cyanide-free extraction of gold from electronic waste by constructing a synergistic system of "double radical activation, bromine recycling, and efficient gold complexation."

[0110] This technology makes a breakthrough by utilizing endogenous bromine in waste as a reaction raw material. In an acidic medium, VA-044 achieves continuous regeneration of bromine free radicals through the synergistic effect of PMS or sodium persulfate. Combined with the dual-functional design of ammonium chloride (Cl- Chromium alloy, NH4 + stable copper ammonia catalyst), forming a complete closed-loop reaction network.

[0111] Experiments have confirmed that this process can achieve a gold leaching rate of over 98% under mild conditions (pH 1-4, room temperature, 1-4 hours), and the leachate is recyclable. This not only addresses industry challenges such as low gold leaching efficiency and severe environmental pollution caused by the complex composition of electronic waste, but also, through the innovative approach of "treating waste with waste," provides an economically feasible and environmentally friendly industrial solution for the recycling of precious metal resources, which is of great significance for promoting the development of a circular economy.

[0112] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling, characterized in that: The steps include: S1, grinding the electronic waste to obtain a slurry with a mass concentration of 1%-10%, and adjusting the pH value of the slurry to 1-4; the electronic waste contains bromine and copper; S2, mixing a compounded free radical initiator with ammonium chloride to obtain a cyanide-free gold leaching agent system; wherein the compounded free radical initiator is a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride) and potassium permonosulfate; in the cyanide-free gold leaching agent system, the mass ratio of the 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride), potassium permonosulfate and ammonium chloride is 1:(1-4):(5-20); Alternatively, the compounded free radical initiator is a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride and sodium persulfate; in the cyanide-free gold leaching agent system, the mass ratio of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride), sodium persulfate and ammonium chloride is 1:(1-4):(5-20); S3, adding the cyanide-free gold leaching agent system to the ore pulp, stirring and reacting for at least 1 hour to obtain a gold-containing precious liquid and a solid residue.

2. The method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling according to claim 1, characterized in that: The bromine element comes from flame retardant materials in electronic waste.

3. The method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling according to claim 1, characterized in that: The electronic waste includes at least one of discarded circuit boards, integrated chips, and discarded electrode materials.

4. The method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling according to claim 1, characterized in that: During the grinding process, the electronic waste is ground to a particle size of less than 100 mesh, and the content accounts for 90%-98% of the total mass of the mineral powder.

5. The method for extracting gold from electronic waste using a cyanide-free gold leaching agent system based on endogenous bromine recycling according to claim 1, characterized in that: The pH value of the slurry is adjusted by adding a pH adjuster; the pH adjuster is hydrochloric acid.

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