Method for extracting gold in electronic waste based on cyanide-free gold leaching agent system for cyclic regeneration of endogenous bromine

Abstract

The invention provides a method for extracting gold in electronic waste based on an endogenous bromine cyclic regeneration cyanide-free gold leaching agent system, and belongs to the technical field of precious metal recycling. According to the method, a compound free radical initiator-ammonium chloride cyanide-free gold leaching agent system is constructed, a bromine-containing flame-retardant material in the electronic waste and ammonium chloride are used for constructing an autocatalytic reaction system, the steady-state concentration of bromine free radicals is remarkably increased, and therefore the gold oxidation capacity is enhanced, and Au < 3 + > is generated by directly oxidizing a gold elementary substance; cl <-> and Au < 3 + > in ammonium chloride introduced in advance are instantly complexed to form [AuCl4] <-> to realize gold leaching, NH4 < + > and copper ions in the system form a copper ammonia complex ([Cu (NH3) 4] < 2 + >) in situ, the complex re-activates inactivated Br <-> into Br <-> in a free radical environment, and a complete closed cycle of bromine free radical oxidation-gold dissolution-bromine ion regeneration is formed. The self-sustaining reaction mechanism not only can stabilize the concentration of the bromine free radicals at the optimal level, but also can realize the gold leaching rate of greater than or equal to 98% under the mild condition.

Description

Technical Field

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

[0002] Currently, gold extraction from electronic waste mainly relies on cyanidation processes, but cyanides are highly toxic and pose safety hazards. Although cyanide-free technologies (such as thiosulfate method, glycine method, etc.) can avoid environmental risks, due to the complex metal components in electronic waste, it is difficult to achieve high-selectivity leaching of gold, resulting in low recovery rates and restricting large-scale applications.

[0003] Currently, the field of gold extraction from electronic waste faces technical bottlenecks and urgently needs to break through the limitations of traditional cyanidation processes and develop new efficient and environmentally friendly cyanide-free gold leaching technologies. Developing new green gold leaching reagents and processes can not only significantly improve the recovery rate of precious metals, but also completely eliminate the environmental and safety risks brought by cyanides, providing key technical support for the sustainable development of the gold industry.

[0004] By innovating cyanide-free gold leaching technologies and achieving efficient recycling of solid waste resources such as electronic waste, the independent controllability of the critical metal supply chain can be enhanced. This breakthrough not only conforms to the country's green development, but also promotes the upgrading of the circular economy industry, providing important support for resource security and ecological civilization construction. Summary of the Invention

[0005] Aiming at the key bottleneck problems such as poor selectivity and low efficiency of current cyanide-free gold leaching reagents in treating electronic waste, the present application provides a method for extracting gold from electronic waste by using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration.

[0006] This method uses the existing bromine-containing flame retardant materials in electronic waste and ammonium chloride to construct a self-catalytic reaction system. Using the bromine-containing flame retardant materials in electronic waste itself as a sustainable bromine source, it produces a synergistic effect with an externally added radical initiator, increasing the gold oxidation efficiency by an order of magnitude. This self-sustaining reaction mechanism can not only stabilize the bromine radical concentration at the optimal level, but also achieve a gold leaching rate of ≥98% under mild conditions (pH 1-4, room temperature), and at the same time, the wastewater can be recycled, fundamentally solving the key scientific problems of large reagent consumption and low efficiency in traditional cyanide-free processes.

[0007] The present application provides a method for extracting gold from electronic waste by using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration, including the following steps: S1, grinding the electronic waste to obtain pulp, and adjusting the pH value of the pulp to a predetermined pH; the electronic waste contains bromine elements and copper elements. S2. Mix the compounded radical initiator with ammonium chloride to obtain a cyanide-free gold leaching reagent system. Among them, the compounded radical initiator is a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and potassium monopersulfate, or a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and sodium persulfate. S3. Add the cyanide-free gold leaching reagent system to the pulp and stir to obtain gold-containing pregnant solution and solid residue.

[0008] Among them, the gold content in the solid residue is tested by the fire assay method, and the test analysis method refers to "GB / T7739".

[0009] Judge the gold leaching situation according to the gold leaching rate.

[0010] In the formula, η represents the gold leaching rate, with the unit of %; m1 represents the mass of the original material, with the unit of g; β1 represents the grade of the original material, with the unit of g / t; m2 represents the mass of the solid residue after leaching, with the unit of g; β2 represents the grade of the solid residue after leaching, with the unit of g / t.

[0011] Detect the gold-containing pregnant solution by ICP-OES, and assist in proving the gold leaching rate according to the gold concentration in the gold-containing pregnant solution. The error between the two methods being less than 1% indicates that the data obtained by this method is valid data.

[0012] Furthermore, the bromine element is derived from the flame retardant material in the electronic waste.

[0013] Furthermore, in the cyanide-free gold leaching reagent system, the mass ratio of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, potassium monopersulfate and ammonium chloride is 1:(1 - 4):(5 - 20).

[0014] Furthermore, in the cyanide-free gold leaching reagent 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).

[0015] Furthermore, in step S3, the stirring reaction time is at least 1 h.

[0016] Furthermore, the predetermined pH is 1 - 4.

[0017] Furthermore, the electronic waste includes at least one of waste circuit boards, integrated chips, and waste electrode materials.

[0018] Further, during the grinding process, the electronic waste is ground to a particle size where the content less than 100 mesh accounts for 90%-98% of the total mass of the ore powder.

[0019] Further, the mass concentration of the pulp is 1%-10%.

[0020] Further, the method for adjusting the pH value of the pulp is to add a pH regulator; the pH regulator is hydrochloric acid.

[0021] The beneficial effects of this application are as follows: 1. This application proposes a method for extracting gold from electronic waste using a cyanide-free gold leaching reagent system based on the endogenous bromine cycle regeneration. The cyanide-free gold leaching reagent system is a compounded free radical initiator-ammonium chloride system. The core of this method lies in synchronously using the bromine-containing flame retardant materials in electronic waste and the externally added ammonium chloride to construct a self-catalytic reaction system. In an acidic medium (pH 1-4), through the compounded free radical initiator (VA-044 / PMS compound or VA-044 / sodium persulfate compound), the flame retardant material is excited to dissociate, generating bromine radicals (Br·). First, the free radical initiator A (PMS or sodium persulfate) decomposes to generate sulfate radicals (·SO4 - ), and this strongly oxidizing 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 to generate carbon-centered radicals (·R) under the same conditions. These radicals can not only directly activate the C-Br bond, but also undergo an electron transfer reaction with the bromide ions (Br - ) generated in the system, re-oxidizing them to Br·, forming a "double radical relay activation" mechanism.

[0022] In addition, the protons (H + ) generated by the decomposition of the free radical initiator A maintain 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.

[0023] This synergistic effect increases the steady-state concentration of bromine radicals by more than 3 times, thus significantly enhancing its oxidation ability towards precious metals (such as gold), directly oxidizing elemental gold to generate Au 3+ ; at the same time, the Cl - previously introduced in ammonium chloride immediately complexes with Au 3+ to form [AuCl4] - to achieve gold leaching, while NH4 + in situ forms a copper-ammonia complex ([Cu(NH3)4] 2+ ) with the copper ions in the system. This complex reactivates the inactivated Br - to Br· in a free radical environment, forming a complete closed-loop cycle of "bromine radical oxidation - gold dissolution - bromide ion regeneration".

[0024] 2. In this application, the bromine-containing flame retardant material in electronic waste itself serves as a sustainable bromine source, generating a synergistic effect with the externally added free radical initiator, which improves the gold oxidation efficiency by an order of magnitude. This self-sustaining reaction mechanism can not only stabilize the bromine radical concentration at the optimal level, but also achieve a gold leaching rate of ≥98% under mild conditions (pH 1-4, room temperature). Meanwhile, the wastewater can be recycled, fundamentally solving the key scientific problems of large 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 utilization of electronic waste.

[0025] 3. By innovatively constructing a bromine radical cycle catalytic system, the present invention achieves the optimal balance of economic and environmental benefits while ensuring technical feasibility. It provides a new approach with both economic feasibility and environmental friendliness for the resource utilization of electronic waste, effectively solving the industry problem that traditional cyanide-free processes are difficult to balance technical performance, economic and environmental benefits.

[0026] The above description is only an overview of the technical solution of this application. In order to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the specific embodiments of this application are specifically given below. Brief Description of the Drawings

[0027] In order to illustrate the technical solution of this application more clearly, the drawings used in this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is the analysis result of the mineral phase dissociation of electronic waste.

[0029] Figure 2 It is the occurrence form of gold in electronic waste.

[0030] Figure 3 It is the occurrence form of copper in electronic waste; among them, (a) is the photo of the copper-containing sample before and after cutting; (b) is the backscattered photo of the sample; (c) is the elemental surface distribution of the sample; (d) is the energy spectrum analysis diagram of the sample elements. Detailed Description of the Embodiments

[0031] The embodiments of the technical solution of this application will be described in detail below with reference to the drawings. The following embodiments are only used to illustrate the technical solution of this application more clearly, so they are only examples and cannot be used to limit the protection scope of this application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field 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 "comprising" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0033] The embodiment of this application provides a method for extracting gold from electronic waste by using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration, which includes the following steps: S1. Grind the electronic waste to obtain a pulp with a preset concentration, and adjust the pH value of the pulp to a predetermined pH. Among them, the electronic waste includes at least one of waste circuit boards, integrated chips, and waste electrode materials.

[0034] The electronic waste contains bromine element and copper element; The bromine element comes from the flame retardant material in the electronic waste.

[0035] The forms of copper element in the electronic waste are pure copper, copper-tin alloy, copper-zinc alloy, and copper-nickel alloy.

[0036] The pure copper comes from the base material of the copper clad laminate.

[0037] The copper-tin alloy comes from the connector elastic contact and lead-free solder.

[0038] The copper-zinc alloy comes from the terminal block, heat dissipation component, and decorative coating.

[0039] The copper-nickel alloy comes from the electroplated anti-corrosion layer (such as the interface coating) and precision resistor components.

[0040] During the grinding process, grind the electronic waste to a particle size less than 100 mesh, and the content accounts for 90%-98% of the total mass of the ore powder.

[0041] Add water to the electronic waste powder and stir to obtain a pulp with a mass concentration of 1%-10%. Then, add the pH regulator hydrochloric acid to adjust the pH of the pulp to 1-4.

[0042] S2. Mix the compounded radical initiator and ammonium chloride to obtain a cyanide-free gold leaching reagent system; Among them, the compounded radical initiator is a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) and potassium monopersulfate (PMS), or a compound solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) and sodium persulfate.

[0043] In the cyanide-free gold leaching reagent system, the mass ratio of VA-044, PMS and ammonium chloride is 1:(1-4):(5-20).

[0044] In the cyanide-free gold leaching reagent system, the mass ratio of VA-044, sodium persulfate and ammonium chloride is 1:(1-4):(5-20).

[0045] S3. Add the cyanide-free gold leaching reagent system to the pulp, stir and react for 1-4 h to obtain gold-containing pregnant solution and solid residue.

[0046] Among them, the gold content in the solid residue is tested by the fire assay method, and the test analysis method refers to 《GB / T7739》.

[0047] Calculate the gold leaching rate and judge the gold leaching situation.

[0048] In the formula, η represents the gold leaching rate, with the unit of %; m1 represents the mass of the original material, with the unit of g; β1 represents the grade of the original material, with the unit of g / t; m2 represents the mass of the solid residue after leaching, with the unit of g; β2 represents the grade of the solid residue after leaching, with the unit of g / t.

[0049] Detect the gold-containing pregnant solution by ICP-OES, and assist in proving the gold leaching rate according to the gold concentration in the gold-containing pregnant solution. The error between the two methods being less than 1% indicates that the data obtained by this method are valid data.

[0050] The following are some specific examples. 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 a limitation of the present application. For those where specific technologies or conditions are not indicated in the examples, the technologies or conditions described in the literature in this field or according to the product specifications are followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0051] Example 1 Select a waste circuit board containing precious metal resources (one kind of electronic waste), and the main components of the waste circuit board are shown in Table 1. Among them, the unit is g / t.

[0052] Table 1 Main components of the waste circuit board * indicates that the unit used is g / t 电子废弃物原料 。

[0053] This example provides a method for extracting gold from electronic waste using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration, including the following steps: S1. Grind the electronic waste into ore powder with a particle size less than 100 mesh and a proportion of 92% to obtain small particle materials; add 50 g of the electronic waste ore powder to 1 L of water and stir. The pulp concentration is 5%. Add hydrochloric acid to adjust the pulp to a pH value of 1.

[0054] The analysis results of the mineral phase dissociation in the electronic waste are as Figure 1 shown. It can be seen that the electronic waste contains copper, bromine, and gold elements.

[0055] Among them, the occurrence forms of gold and copper elements are as Figure 2 、 Figure 3 shown.

[0056] S2. Mix the compounded free radical initiator and ammonium chloride to obtain a cyanide-free gold leaching reagent system; among them, the compounded free radical initiator is a compound solution of VA-044 and PMS; specifically, 0.5 g of VA-044, 2 g of PMS, and 5 g of ammonium chloride, that is, the mass ratio of VA-044, PMS, and ammonium chloride is 1:4:10.

[0057] S3. Add the cyanide-free gold leaching reagent system to the pulp and stir for 1 h to obtain gold-containing pregnant solution and solid residue.

[0058] Among them, the gold content in the solid residue is tested by the fire assay method, and the test analysis method refers to "GB / T7739".

[0059] Calculate the gold leaching rate to judge the gold leaching situation.

[0060] In the formula, η represents the gold leaching rate, with the unit of %; m1 represents the mass of the original material, with the unit of g; β1 represents the grade of the original material, with the unit of g / t; m2 represents the mass of the solid residue after leaching, with the unit of g; β2 represents the grade of the solid residue after leaching, with the unit of g / t.

[0061] Detect the gold-containing pregnant solution by ICP-OES, and assist in proving the gold leaching rate obtained by the method of this application according to the gold concentration in the gold-containing pregnant solution. 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.

[0062] Example 2 Example 2 provides a method for extracting gold from electronic waste using a cyanide-free gold leaching reagent system based on the endogenous bromine cycle regeneration. Compared with Example 1, the difference is that the type of the compounded free radical initiator used is different, as shown in Table 2. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0063] Table 2 Types of compound free radical initiators in Examples 1-2 and leaching rates of gold and copper As can be seen from Table 2, in Examples 1-2, high-efficient leaching of gold can be achieved (both reaching 98%). Among them, the synergistic oxidation-catalysis mechanism of the compound free radical initiator is as follows: in an acidic medium, potassium monopersulfate (PMS) or sodium persulfate first decomposes to generate strongly oxidizing free radicals (·SO4 - ), which directly oxidize the brominated flame retardant in the electronic waste to generate bromine free radicals (Br·), and then attack elemental gold to form Au 3+ ; at the same time, the carbon-centered free radicals (·R) generated by the decomposition of the water-soluble azo initiator VA-044 not only assist in activating the C-Br bond, but also re-convert the reaction by-product Br - back to Br· through electron transfer, forming a bromine free radical recycling network. Although the copper ammonia complex ([Cu(NH3)4] 2+ ) dissociates dynamically under acidic conditions, the dissociated Cu 2+ and NH4 + still participate in the catalytic oxidation of Br - through rapid coordination equilibrium, and the local micro-alkaline environment provided by NH4 + delays the complete decomposition of the complex. This synergistic effect of "double free radical triggering-copper ammonia dynamic catalysis" not only ensures the continuous supply of bromine free radicals, but also realizes the stable dissolution of gold through the efficient complexation of Cl - (from NH4Cl) and Au 3+ , and finally achieves complete leaching of gold under cyanide-free conditions.

[0064] Examples 3-4 and Comparative Examples 1-2 Examples 3-4 and Comparative Examples 1-2 provide a method for extracting gold from electronic waste using a cyanide-free gold leaching reagent system based on endogenous bromine recycling. Compared with Example 1, the difference lies in that in step S1, the pulp concentration is different. As shown in Table 3, other experimental parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0065] Table 3 Pulp concentrations and gold and copper leaching rates in Examples 3-4 and Comparative Examples 1-2 As can be seen from Table 3, the pulp concentration has a significant effect on the gold leaching efficiency. When the pulp 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 at a high level of 93%.

[0066] This phenomenon reveals three key mechanisms: First, a high pulp concentration leads to an increase in the solid content per unit volume, but the dosage of reagents is not correspondingly increased, resulting in insufficient effective concentrations of the free radical initiator and ammonium chloride, unable to meet the kinetic requirements of the gold oxidation-complexation reaction; Second, the preferential formation of copper-ammonia complexes further inhibits the leaching of gold under reagent-limited conditions; Third, experiments confirm that this process can maintain a gold leaching rate of over 96% within a pulp concentration range of 1-10%, providing a clear concentration control window for industrial applications and ensuring leaching efficiency and economic benefits.

[0067] Examples 5-12 and Comparative Examples 3-8 Examples 5-12 and Comparative Examples 3-8 provide a method for extracting gold from electronic waste using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration. Compared with Example 1, the difference lies in that the dosage ratios of the components in the cyanide-free gold leaching reagent system are different, as shown in Table 4 specifically. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0068] Table 4 Dosage ratios of the components in Examples 5-12 and Comparative Examples 3-8 and gold leaching rates As can be seen from Table 4, the reagent component ratio is a key factor affecting the gold leaching efficiency.

[0069] When the mass ratio of VA-044, PMS to 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 for bromine free radical generation, gold oxidation and complexation dissolution.

[0070] It is worth noting that when the mass ratio of ammonium chloride to VA-044 increases from 5:1 to 10:1, the leaching rate further increases from 98% to 99%, confirming the importance of sufficient ammonium chloride in maintaining the gold complexation dissolution equilibrium. In contrast, too high a proportion of VA-044 (Comparative Examples 3-5) or too low a proportion of ammonium chloride (Comparative Examples 6-8) will lead to a significant decrease in the leaching rate (49%-92%), which verifies the necessity of the synergistic effect of the three reagent components.

[0071] The optimal ratio of 1:(1-4):(5-20) not only ensures the efficient cyclic regeneration of bromine free radicals but also provides sufficient gold complexation sites, thus achieving a stable and efficient gold leaching effect. These results provide a scientific basis for the precise control of reagent ratios in industrial applications.

[0072] Examples 13-15 and Comparative Examples 9-11 Examples 13 - 15 and Comparative Examples 9 - 11 provide a method for extracting gold from electronic waste using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration. Compared with Example 1, the difference lies in the pH value of the pulp, as shown in Table 5. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0073] Table 5 pH values of the pulp and gold leaching rates in Examples 13 - 15 and Comparative Examples 9 - 11 — represents below the detection limit of ICP - OES. Considering the detection error, the gold leaching rate is almost 0.

[0074] As can be seen from 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 dual promoting effects of the acidic environment on the generation of bromine radicals (PMS decomposes into ·SO4 - ), and the complexation and dissolution of gold ([AuCl4] - formation). However, when the pH rises to 5, the leaching rate drops significantly to 87%, and drops sharply to 35% at pH 6. Under weakly alkaline conditions (pH = 8), the leaching reaction almost completely terminates.

[0075] This phenomenon is mainly attributed to: First, the decomposition efficiency of PMS decreases under neutral to alkaline conditions, resulting in insufficient generation of bromine radicals; Second, the dissociation of copper ammonia complexes promoted by the increase in pH disrupts the catalytic regeneration cycle of bromide ions; Third, the stability of gold complexes decreases significantly with the increase in pH. These findings provide a clear process control window (pH 1 - 4) for industrial applications, and at the same time emphasize the key role of maintaining an acidic environment in this technology.

[0076] Examples 16 - 18 and Comparative Examples 12 - 13 Examples 16 - 18 and Comparative Examples 12 - 13 provide a method for extracting gold from electronic waste using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration. Compared with Example 1, the difference lies in the stirring reaction time, as shown in Table 6. Other experimental parameters and conditions are basically the same as those in Example 1 and will not be elaborated here.

[0077] Table 6 Stirring reaction times and gold leaching rates in Examples 16 - 18 and Comparative Examples 12 - 13 As can be seen from Table 6, the influence rule of stirring time on the gold leaching efficiency is as follows: when the reaction time is increased from 0.5 h (Comparative Example 12) to 1 h (Example 1), the gold leaching rate significantly jumps from 86% to 98%, indicating that 1 h is the key time node for the reaction to reach basic equilibrium; when the stirring time is further extended to 2 - 5 h (Examples 16 - 18 and Comparative Example 13), the leaching rate remains in the stable range of 98 - 99%, confirming that the reaction system has tended to be complete after 4 h.

[0078] This phenomenon shows that: 1) The generation of bromine radicals and the complex dissolution of gold require at least 1 h to complete the main reaction process; 2) Too short a time (0.5 h) will lead to insufficient oxidation - complexation reaction, while excessive extension (>4 h) will not increase the marginal benefit (from 99% to 100%). Therefore, controlling the stirring time within 1 - 4 h can not only ensure the maximization of leaching efficiency but also avoid the waste of energy and time resources.

[0079] In summary, the present invention provides a method for extracting gold from electronic waste using a cyanide - free gold leaching agent system based on endogenous bromine cycle regeneration. This method realizes the cyanide - free and green extraction of gold from electronic waste by constructing a synergistic system of "dual - radical activation - bromine cycle regeneration - high - efficiency gold complexation".

[0080] This technology breakthroughly uses the endogenous bromine in waste as a reaction raw material, and realizes the continuous regeneration of bromine radicals through the synergistic effect of VA - 044 and PMS or sodium persulfate in an acidic medium. Combined with the dual - functional design of ammonium chloride (Cl - complexing gold, NH4 + stabilizing the copper - ammonia catalyst), a complete closed - loop reaction network is formed.

[0081] 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 h), and the leaching solution can be recycled. This not only solves the industry problems such as low gold leaching efficiency and large environmental pollution caused by the complex components of electronic waste, but also provides an industrial solution with both economic feasibility and environmental friendliness for the recycling of precious metal resources through the innovative idea of "treating waste with waste", which is of great significance for promoting the development of circular economy.

[0082] It should be noted that this application is not limited to the above - mentioned embodiments. The above - mentioned embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the main idea of this application, various deformations that those skilled in the art can think of and other ways constructed by combining some components in the embodiments are also included in the scope of this application.

Claims

1. A method for extracting gold from electronic waste by a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration, characterized in that, It includes the following steps: S1. Grind the electronic waste to obtain pulp, and adjust the pH value of the pulp to a predetermined pH; the electronic waste contains bromine element and copper element; S2. Mix the compounded radical initiator and ammonium chloride to obtain a cyanide-free gold leaching reagent system; wherein, the compounded radical initiator is a compounded solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and potassium monopersulfate, or a compounded solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and sodium persulfate; S3. Add the cyanide-free gold leaching reagent system to the pulp and stir to obtain gold-containing pregnant solution and solid residue.

2. The method for extracting gold from electronic waste by using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration according to claim 1, characterized in that, The bromine element is derived from the flame retardant material in the electronic waste.

3. The method for extracting gold from electronic waste by using a cyanide-free gold leaching agent system based on endogenous bromine cycle regeneration according to claim 1, wherein, In the cyanide-free gold leaching reagent system, the mass ratio of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, potassium monopersulfate and ammonium chloride is 1:(1-4):(5-20).

4. The method for extracting gold from electronic waste by using a cyanide-free gold leaching agent system based on endogenous bromine cycle regeneration according to claim 1, characterized in that, In the cyanide-free gold leaching reagent 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).

5. The method for extracting gold from electronic waste by using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration according to claim 1, wherein, In step S3, the stirring reaction time is at least 1 h.

6. The method for extracting gold from electronic waste by using a cyanide-free gold leaching agent system based on endogenous bromine cycle regeneration according to claim 1, characterized in that, The predetermined pH is 1-4.

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

8. The method for extracting gold from electronic waste by using a cyanide-free gold leaching agent system based on endogenous bromine cycle regeneration according to claim 1, wherein, During the grinding treatment, grind the electronic waste to a particle size less than 100 mesh, and the content accounts for 90%-98% of the total mass of the ore powder.

9. The method for extracting gold from electronic waste by using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration according to claim 1, wherein The mass concentration of the pulp is 1%-10%.

10. The method for extracting gold from electronic waste by using a cyanide-free gold leaching reagent system based on endogenous bromine cycle regeneration according to claim 1, wherein The method for adjusting the pH value of the pulp is to add a pH value regulator; the pH value regulator is hydrochloric acid.

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