A method for extracting gold resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system

Abstract

This application provides a method for extracting gold resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system, which belongs to the technical field of precious metal recycling. This method utilizes the original copper / iron impurities in discarded printed circuit boards to construct a Cu 2+ / Fe 3+ TEMPO redox coupled synergistic catalytic system. 2+ (E°=0.34 V vs SHE) and Fe 3+ (E°=0.77 V) with TEMPO + (E°=0.75 V) forms a step-by-step electron transport chain. TEMPO is precisely controlled by electric field + The electron transfer efficiency of the TEMPO redox couple (E° = 0.75 V vs. SHE) significantly increases the gold dissolution rate while reducing energy consumption and achieving a low impurity co-dissolution rate, enabling efficient and selective recovery of gold resources from electronic waste. This invention, through the TEMPO electrocatalytic-histidine chelation synergistic system, achieves efficient and selective extraction of gold from urban minerals, fundamentally addressing the key challenges of traditional cyanide-free gold extraction processes, such as high oxidant consumption, poor selectivity, and low efficiency.

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 resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching agent system. 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. Developing 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 my country's gold industry.

[0004] Through innovative cyanide-free gold extraction technology, efficient recycling of solid waste resources such as electronic waste can be achieved, effectively alleviating my country's dependence on foreign gold resources and enhancing the independent and controllable supply chain for key metals. This breakthrough not only aligns with the national green development strategy 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 view of the technical problems existing in the background technology, this application provides a method for extracting gold resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system. This method utilizes the original copper / iron impurities in waste printed circuit boards (WPCBs) to construct Cu 2+ / Fe 3+ -TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) redox coupled synergistic catalytic system.

[0006] The in-situ generated Cu 2+ (E°=0.34 V vs SHE) and Fe 3+ (E°=0.77 V) and TEMPO⁺ (E°=0.75 V) form a step-by-step electron transport chain. 2+ (E°=0.34 V) → TEMPO + (E°=0.75 V) → Fe 3+ (E°=0.77 V)→Au 3+ (E°=1.50 V)cascade electron transfer path. Among them, Fe 2+ / Fe3+ The redox couple realizes the dynamic regeneration cycle of the catalyst. TEMPO is oxidized at the anode to generate highly active oxygen ammonium ions (TEMPO + ), Au is gradually transferred to the 0 Oxidized to Au 3+ (TEMPO + +Au 0 →TEMPO+Au + TEMPO + +Au + → TEMPO+Au 3+ ), while the cathode oxygen reduction reaction (O2+2H2O+4e - → 4OH - ) Dynamically maintain the alkaline environment of the system; dissolved Au 3+ With histidine anion (His - ) forms a stable [Au(His)2] + Complex. Among them, Au 3+ (d 8 Soft acid) preferentially reacts with His - The imidazole nitrogen (Nπ, soft base) forms a strong covalent bond, and the coordinated coordination of the carboxylic acid oxygen (O) not only enhances the water solubility, but also repels Cu through steric hindrance and coordination field stabilization. 2+ / Fe 3+ Impurity ions (selectivity coefficient of 1.2×10 4 The reduction product TEMPO-H (hydroxylamine) in the system can be reversibly regenerated into TEMPO (TEMPO-H–e - → TEMPO+ H + ), and O2 / OH - The cycles form a closed catalytic network.

[0007] This method precisely regulates TEMPO by controlling the electrolysis voltage. + The electron transfer efficiency of the TEMPO redox couple (E°=0.75 V vs. SHE) increases the gold dissolution rate by 10 times compared to the traditional cyanide-free process, while reducing energy consumption and the impurity co-dissolution rate, achieving efficient and selective recovery of gold resources in electronic waste.

[0008] The present application provides a method for extracting gold resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching reagent system, comprising the following steps:

[0009] S1, grinding the electronic waste to obtain a slurry, and adjusting the pH value of the slurry to a predetermined pH; the electronic waste contains copper and iron elements;

[0010] S2, mixing 2,2,6,6-tetramethylpiperidin-1-oxide free radical and histidine and adding the mixture to the ore pulp to obtain a mixed solution; using a graphite electrode as an anode, a titanium-based platinum-plated mesh counter electrode as a cathode, and a double salt bridge as a reference electrode to form a three-electrode system, using the mixed solution as an electrolyte, and performing constant voltage electrolysis treatment to obtain a precious liquid containing gold 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, in the mixed solution, the concentration of the 2,2,6,6-tetramethylpiperidin-1-oxyl free radical is 0.05-0.5 mol / L.

[0017] Furthermore, in the mixed solution, the concentration of histidine is greater than or equal to 0.5 mol / L, preferably 0.5-2 mol / L.

[0018] Furthermore, during the constant voltage electrolysis treatment, the voltage range is 5-20V and the treatment time is 2-3h.

[0019] Furthermore, the predetermined pH is 8-14.

[0020] Furthermore, the electronic waste includes at least one of discarded circuit boards, integrated chips, and discarded electrode materials.

[0021] 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.

[0022] Furthermore, the mass concentration of the slurry is 1%-10%.

[0023] Furthermore, the pH value of the slurry is adjusted by adding a pH regulator; the pH regulator is sodium hydroxide.

[0024] Furthermore, during the constant voltage electrolysis treatment, the stirring speed is 400-700 rpm.

[0025] The beneficial effects of this application are:

[0026] 1. This application proposes a method for extracting gold resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system. This method utilizes the original copper / iron impurities in waste printed circuit boards (WPCBs) to construct a Cu 2+ / Fe 3+ -TEMPO redox coupled synergistic catalytic system. 2+ (E°=0.34 V vs SHE) and Fe 3+ (E°=0.77 V) with TEMPO + (E°=0.75 V)forms a step-by-step electron transport chain. That is, under electrochemical drive, Cu 2+ (E°=0.34 V) → TEMPO + (E°=0.75 V) → Fe 3+ (E°=0.77 V)→Au 3+ (E°=1.50 V) cascade electron transfer pathway, where Fe 2 + / Fe 3+ The redox couple realizes a dynamic regeneration cycle of the catalyst.

[0027] 2. In this application, TEMPO generates highly active oxygen ammonium ions (TEMPO + ), Au is gradually transferred to the 0 Oxidized to Au 3+ (TEMPO + +Au 0 →TEMPO+Au + TEMPO + +Au + →TEMPO+ Au 3+ ), while the cathode oxygen reduction reaction (O2+2H2O+4e - → 4OH - ) Dynamically maintain the alkaline environment of the system; dissolved Au 3+ With histidine anion (His - ) forms a stable [Au(His)2] + Complex. Among them, Au 3+ (d 8 Soft acid) preferentially reacts with His -The imidazole nitrogen (Nπ, soft base) forms a strong covalent bond, and the coordinated coordination of the carboxylic acid oxygen (O) not only enhances the water solubility, but also repels Cu through steric hindrance and coordination field stabilization. 2+ / Fe 3+ Impurity ions (selectivity coefficient of 1.2×10 4 The reduction product TEMPO-H (hydroxylamine) in the system can be reversibly regenerated into TEMPO (TEMPO-H–e - → TEMPO+H + ), and O2 / OH - The cycles form a closed catalytic network.

[0028] 3. This application precisely controls TEMPO by controlling the electrolysis voltage + The electron transfer efficiency of the TEMPO redox couple (E°=0.75 V vs. SHE) increases the gold dissolution rate by 10 times compared to the traditional cyanide-free process, while reducing energy consumption and the impurity co-dissolution rate, achieving efficient and selective recovery of gold resources in electronic waste.

[0029] 4. The present invention achieves efficient and selective extraction of gold from urban minerals through a TEMPO electrocatalytic-histidine chelation synergistic system, fundamentally solving the key problems of high oxidant consumption, poor selectivity, and low efficiency in traditional cyanide-free gold extraction processes, and provides a new green, efficient, and economically sustainable solution for the resource utilization of electronic waste.

[0030] 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

[0031] 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.

[0032] Figure 1 This is a physical picture of electronic waste raw materials.

[0033] Figure 2 It is the storage form of copper in electronic waste.

[0034] Figure 3 It is the storage form of iron in electronic waste. DETAILED DESCRIPTION

[0035] 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.

[0036] 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.

[0037] The present invention provides a method for extracting gold resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching reagent system, comprising the following steps:

[0038] 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; the electronic waste contains copper and iron elements;

[0039] Electronic waste includes at least one of discarded circuit boards, integrated chips, and discarded electrode materials.

[0040] The copper element comes from the copper matrix in urban minerals.

[0041] The iron element comes from iron components in urban mines.

[0042] 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.

[0043] Water is added to the electronic waste powder and stirred to obtain a slurry with a mass concentration of 1%-10%.

[0044] The pH value of the slurry is adjusted by adding sodium hydroxide as a pH adjuster, and the predetermined pH value is 8-14.

[0045] S2, mixing 2,2,6,6-tetramethylpiperidin-1-oxide free radical and histidine and adding them to the ore pulp to obtain a mixed solution; using a graphite electrode as the anode, a titanium-based platinum-plated mesh counter electrode as the cathode, and a double salt bridge as the reference electrode to form a three-electrode system, using the mixed solution as the electrolyte, constant voltage electrolysis treatment is carried out to obtain a precious liquid containing gold and a solid residue.

[0046] In the mixed solution, the concentration of 2,2,6,6-tetramethylpiperidin-1-oxyl free radical is 0.05-0.5 mol / L, and the concentration of histidine is greater than or equal to 0.5 mol / L, preferably 0.5-2 mol / L.

[0047] During the constant voltage electrolysis treatment, the voltage range is 5-20 V, the stirring speed is 400-700 rpm, and the treatment time is 2-3 h.

[0048] 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".

[0049] Calculate the gold leaching rate and determine the gold leaching situation.

[0050]

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Example 1

[0055] Waste circuit boards containing precious metal resources (a type of urban mineral resources) were selected, and the main components of the waste circuit boards are shown in Table 1. The unit is g / t.

[0056] Table 1 Main components of waste circuit boards

[0057]

[0058] *Indicates the unit used is g / t 电子废弃物原料 .

[0059] See also Figure 1 As shown, this embodiment provides a method for extracting gold resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching reagent system, comprising the following steps:

[0060] S1, grinding the electronic waste to a particle size of less than 100 mesh, accounting for 92% of the mineral powder, to obtain small particles, adding water to the electronic waste powder and stirring, the slurry concentration is 5%, adding sodium hydroxide to adjust the slurry to a pH of 12; electronic waste contains copper and iron elements, wherein the occurrence forms of copper and iron elements are as follows Figure 2 、 Figure 3 shown.

[0061] S2, the graphite electrode was mechanically polished (400# sandpaper), ultrasonically cleaned (using ethanol and water for 30 min each), and electrochemically activated (cyclic voltammetry scan for 20 cycles in 0.5 M H2SO4);

[0062] A 3L cylindrical electrolytic cell was used to mix 2,2,6,6-tetramethylpiperidin-1-oxyl radical (TEMPO) and histidine and then added to the ore pulp to obtain a mixed solution; wherein the concentration of TEMPO was 0.2 mol / L and the concentration of histidine was 1 mol / L;

[0063] A three-electrode system was constructed with a graphite electrode as the anode, a titanium-based platinum-plated mesh counter electrode as the cathode, and a double salt bridge as the reference electrode. The above-mentioned mixed solution was used as the electrolyte, and constant voltage electrolysis was carried out for 2.5 hours to obtain a precious gold solution and a solid residue.

[0064] During the constant voltage electrolysis treatment, the voltage was 10 V and the stirring speed was 500 rpm.

[0065] 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".

[0066] Calculate the gold leaching rate and determine the gold leaching situation.

[0067]

[0068] 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.

[0069] 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.

[0070] Examples 2-7 and Comparative Example 1

[0071] Examples 2-7 and Comparative Example 1 provide a method for extracting gold resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching agent system. Compared with Example 1, the difference is that in step S1, the pH value of the slurry is different (the pH value is adjusted to a predetermined value using sodium hydroxide), as shown in Table 2. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0072] Table 2 pH value and gold leaching rate of Examples 2-7 and Comparative Example 1

[0073]

[0074] — represents the value below the detection limit of ICP-OES. Taking into account the detection error, the gold leaching rate is close to 0.

[0075] As shown in Table 2, when the pulp pH = 7 (Comparative Example 1), the gold leaching rate is lower than the detection limit (almost 0). This result directly confirms that histidine (His) cannot effectively dissociate into anionic form (H - ), resulting in failure of gold dissolution. This phenomenon can be traced back to the inhibition of histidine protonation, that is, the imidazole group (pKa = 6.0) and carboxyl group (pKa = 1.8) of histidine are still partially protonated (-COOH and -NH + ), cannot provide enough lone pair electrons to react with Au 3+ Coordination. Loss of coordination ability: The undissociated histidine molecule (HisH) can only be weakly coordinated through the neutral nitrogen atom, and the [Au(HisH)3] 3+ The stability constant of the complex is much lower than that of the anionic form [Au(His)2] + , and its water solubility is significantly reduced; In addition, in a neutral environment, [Au(HisH)3] 3+ It is easily hydrolyzed to form Au(OH)3 precipitate, which further hinders the reaction.

[0076] The high leaching rate (≥95%) of Examples 1-7 shows that histidine can be fully deprotonated when pH is ≥8. - The efficient and selective leaching of gold was achieved through the bidentate coordination of imidazole nitrogen (Nπ) and carboxylic acid oxygen (O), which reflects the necessity of alkaline environment for ligand activation.

[0077] Examples 8-14 and Comparative Examples 2-3

[0078] Examples 8-14 and Comparative Examples 2-3 provide a method for extracting gold resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching agent system. Compared with Example 1, the difference is that in step S2, the concentration of TEMPO 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.

[0079] Table 3 TEMPO concentration and gold leaching rate of Examples 8-14 and Comparative Examples 2-3

[0080]

[0081] As shown in Table 3, the nonlinear relationship between TEMPO concentration and gold leaching rate shows a typical "plateau effect".

[0082] When the TEMPO concentration was lower than 0.05 mol / L, the gold leaching rate dropped sharply to 32-72% (Comparative Examples 2-3), indicating that the system was in the reactant-limited region and the lack of TEMPO prevented the oxidation reaction from proceeding completely.

[0083] In the concentration range of 0.2-0.5 mol / L (Examples 1, 10-12), the leaching rate reached a stable platform of 97-99%, indicating that the reaction has now shifted to the gold surface reaction control area. It is worth noting that even if the TEMPO concentration is further increased to 0.6-1 mol / L (Examples 13-14), the leaching rate remains at 99% but does not increase significantly, confirming the existence of a kinetic saturation point in the reaction. This phenomenon can be explained from the electrochemical catalytic mechanism: TEMPO, as an electron mediator, has a redox cycle rate that can meet the Au surface reaction requirements at 0.5 mol / L. 0 Complete oxidation is required, and too high a concentration will only increase costs without improving efficiency.

[0084] Meanwhile, the sudden drop in leaching rate observed at low concentrations (<0.05 mol / L) is likely related to competing side reactions (such as surface passivation caused by direct oxidation by dissolved oxygen) and the obstruction of the TEMPO regeneration cycle. Therefore, 0.05-0.5 mol / L was identified as the optimal concentration window, which ensures complete reaction while maintaining optimal economic efficiency.

[0085] Examples 15-19 and Comparative Example 4

[0086] Examples 15-19 and Comparative Example 4 provide a method for extracting gold resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching reagent system. Compared with Example 1, the difference is that in step S2, the concentration of histidine 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.

[0087] Table 4 Histidine concentration and gold leaching rate of Examples 15-19 and Comparative Example 4

[0088]

[0089] As shown in Table 4, the concentration of histidine has a significant effect on the gold leaching rate.

[0090] When the histidine concentration was in the range of 0.5–2 mol / L (Examples 1 and 15–17), the gold leaching rate remained at a high level of 92%–99%, indicating that this concentration range could effectively stabilize the gold ions in the TEMPO electrocatalytic system and form a stable complex with gold through the carboxyl and amino groups of histidine, thereby promoting the dissolution of gold.

[0091] However, when the histidine concentration fell below 0.5 mol / L (Comparative Example 4), the leaching rate plummeted to 71%, indicating that insufficient histidine reduced gold complexing ability and failed to fully maintain the electrocatalytic-dissolution equilibrium. Furthermore, when the histidine concentration exceeded 2.5 mol / L (Examples 18-19), the leaching rate remained at 99% but did not increase further, possibly due to saturation of complexing sites or increased solution viscosity, which limited mass transfer efficiency. In summary, the optimal histidine concentration range is 0.5-2 mol / L, at which point it achieves the optimal balance between the catalytic oxidation effect of TEMPO and its gold ion complexing ability.

[0092] Examples 20-21 and Comparative Examples 5-6

[0093] Examples 20-21 and Comparative Examples 5-6 provide a method for extracting gold resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching agent system. Compared with Example 1, the difference is that the concentration 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.

[0094] Table 5 Slurry concentration and gold leaching rate of Examples 20-21 and Comparative Examples 5-6

[0095]

[0096] It can be seen from Table 5 that the slurry concentration has a significant effect on the gold leaching rate, and its mechanism of action is mainly related to the metal content, effective concentration of the reagent and mass transfer efficiency.

[0097] When the slurry concentration is low (1%-10%, Examples 1, 20, and 21), the leaching rate is high (91%-99%). This is because the low slurry concentration results in a low metal content per unit volume, allowing the reagents (such as TEMPO and histidine) to fully contact and dissolve the gold. Furthermore, the low solids content facilitates mass transfer and diffusion. However, as the slurry concentration increases (11%-15%, Comparative Examples 5 and 6), the leaching rate gradually decreases (76%-83%). This may be due to the increase in solid particles leading to excessively high local metal concentrations and a relatively insufficient amount of reagents. Furthermore, the increased slurry viscosity hinders mass transfer, making it difficult for the reagents to effectively diffuse to the gold surface and participate in the reaction.

[0098] Therefore, controlling the slurry concentration to a low level (1%-10%) optimizes leaching efficiency, while excessively high concentrations can weaken leaching results due to mass transfer limitations and reagent competition. Finally, the process maintains a gold leaching rate of over 90% within a slurry concentration range of 1-10%, providing a clear concentration control window for industrial applications, ensuring leaching efficiency and economic benefits.

[0099] Examples 22-25 and Comparative Examples 7-9

[0100] Examples 22-25 and Comparative Examples 7-9 provide a method for extracting gold resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching agent system. Compared with Example 1, the difference is that in step S2, the voltage during constant voltage electrolysis treatment is different, as shown in Table 6. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0101] Table 6 Voltage and gold leaching rate of Examples 22-25 and Comparative Examples 7-9

[0102]

[0103] As shown in Table 6, the voltage has a significant effect on the gold leaching rate, and its mechanism is closely related to the electrocatalytic oxidation efficiency and the competition of side reactions.

[0104] At lower voltages (5-15 V), the gold leaching rate was higher (92%-98%), indicating that TEMPO electrocatalytic oxidation of gold was dominant and that histidine effectively stabilized the dissolved gold ions.

[0105] However, when the voltage exceeded 15 V (Example 25 and Comparative Examples 7-8), the leaching rate began to decrease (92% → 80% → 29%), indicating that significant side reactions (such as electrolytic oxygen production by water, excessive oxidation and deactivation of TEMPO, or secondary deposition of gold) may occur at this time, resulting in a decrease in the effective current efficiency.

[0106] In particular, side reactions intensified dramatically at voltages ≥21 V (the leaching rate in Comparative Example 8 plummeted to 29%), indicating that the system had exceeded the optimal window for electrocatalytic oxidation. Overly strong oxidizing power, however, disrupted the reaction equilibrium. Furthermore, at low potentials (Comparative Example 9, 4.5 V), the leaching rate was only 6%, indicating that the energy driving TEMPO oxidation of gold was insufficient to effectively overcome the energy barrier for gold dissolution.

[0107] Therefore, the optimal constant voltage range is 5-20 V. At this time, the catalytic oxidation of TEMPO and the complexation of histidine are most synergistic, and the side reactions are controllable.

[0108] Examples 26-27 and Comparative Examples 10-13

[0109] Examples 26-27 and Comparative Examples 10-13 provide a method for extracting gold resources from urban minerals based on a TEMPO electrocatalysis-histidine gold leaching agent system. Compared with Example 1, the difference is that in step S2, the time of constant voltage electrolysis treatment is different, as shown in Table 7. Other experimental parameters and conditions are basically the same as those in Example 1 and are not repeated here.

[0110] Table 7 Treatment time and gold leaching rate of Examples 26-27 and Comparative Examples 10-13

[0111]

[0112] It can be seen from Table 7 that the leaching time has an effect on the gold leaching rate, which first increases and then decreases.

[0113] Specifically, within the 2-3 hour range (Examples 1, 26, and 27), the leaching rate reached 92% to 98%, indicating that the electrocatalytic activity of TEMPO and the complexation with histidine were sufficient within this time period.

[0114] However, when the reaction time is too short (1-1.5 hours, Comparative Examples 10-11), incomplete reaction results in low leaching yields (56%-82%). When the reaction time exceeds 3 hours (3.5-6 hours, Comparative Examples 12-13), the leaching yield drops significantly (75% → 37%). This may be due to the prolonged reaction time leading to TEMPO decomposition, gold ion redeposition, or the accumulation of harmful byproducts (such as oxidative degradation products) in the solution, which inhibits the continued dissolution of gold. Therefore, the optimal leaching time should be controlled between 2-3 hours to ensure efficient gold leaching while avoiding the exacerbation of side reactions.

[0115] In summary, the present invention provides a method for extracting gold resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system. This method utilizes copper / iron impurities in waste printed circuit boards (WPCBs) to construct a self-sustaining Cu 2+ / Fe 2+ / Fe3+ -TEMPO multi-level catalytic network.

[0116] The system forms Cu by precisely controlling the redox potential gradient. 2+ (E°=0.34 V) → TEMPO + (E°=0.75 V)→ / Fe 3+ (E°=0.77 V) → Au 3+ (E°=1.50 V)cascade electron transfer path. Among them, Fe 2+ / Fe 3+ The redox couple realizes the dynamic regeneration cycle of the catalyst. The introduction of histidine not only forms a highly stable [Au(His)2] 3+ The complex selectively stabilizes gold ions and also regulates the Au 3+ / Au + The potential shifted negatively, significantly improving the reaction kinetics. In the optimal process parameter range, it showed triple synergistic advantages: (1) Cu 2+ As an electron bridge to promote TEMPO activation, (2) Fe 3+ / Fe 2 + The circulation maintains the oxidative capacity, (3) histidine inhibits gold hydrolysis and avoids interference from impurities.

[0117] This method provides an industrial solution for the recycling of precious metal resources that is both economically feasible and environmentally friendly, and is of great significance to promoting the development of the circular economy.

[0118] 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 resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system, characterized in that: The steps include: S1, grinding the electronic waste to obtain a pulp, and adjusting the pH value of the pulp to a predetermined pH value; the electronic waste contains copper and iron elements; the predetermined pH value is 8-14; S2, mixing 2,2,6,6-tetramethylpiperidin-1-oxyl free radical and histidine and adding the mixture to the ore pulp to obtain a mixed solution; using a graphite electrode as an anode, a titanium-based platinum-plated mesh counter electrode as a cathode, and a double salt bridge as a reference electrode to form a three-electrode system, using the mixed solution as an electrolyte, and performing constant voltage electrolysis treatment to obtain a precious gold solution and a solid residue; during the constant voltage electrolysis treatment, the voltage range is 5-20V.

2. The method for extracting gold resources from urban minerals based on the TEMPO electrocatalysis-histidine gold leaching reagent system according to claim 1, characterized in that: In the mixed solution, the concentration of the 2,2,6,6-tetramethylpiperidin-1-oxyl free radical is 0.05-0.5 mol / L.

3. The method for extracting gold resources from urban minerals based on the TEMPO electrocatalysis-histidine gold leaching reagent system according to claim 1, characterized in that: In the mixed solution, the concentration of histidine is greater than or equal to 0.5 mol / L.

4. The method for extracting gold resources from urban minerals based on the TEMPO electrocatalysis-histidine gold leaching reagent system according to claim 1, characterized in that: When the constant voltage electrolysis treatment is carried out, the treatment time is 2-3 hours.

5. The method for extracting gold resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system according to claim 1, characterized in that: The electronic waste includes at least one of discarded circuit boards, integrated chips, and discarded electrode materials.

6. The method for extracting gold resources from urban minerals based on the TEMPO electrocatalysis-histidine gold leaching reagent system 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.

7. The method for extracting gold resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system according to claim 1, characterized in that: The mass concentration of the ore pulp is 1%-10%.

8. The method for extracting gold resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system according to claim 1, characterized in that: The pH value of the slurry is adjusted by adding a pH regulator; the pH regulator is sodium hydroxide.

9. The method for extracting gold resources from urban minerals based on TEMPO electrocatalysis-histidine gold leaching reagent system according to claim 1, characterized in that: During the constant voltage electrolysis treatment, the stirring speed is 400-700 rpm.

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