Copper extraction reagent system and method for recovering copper from waste printed circuit boards

Abstract

The application provides a copper extraction reagent system and a method for recovering copper from waste printed circuit boards, and belongs to the technical field of hydrometallurgy. The application constructs a copper extraction mechanism of "adsorption-electrolysis activation-oxidation-complexation", and a nitrogen-containing organic salt complex precursor with a specific structure is adsorbed on the surface of copper of the printed circuit board. Under the action of electrolysis, chlorine ions are in-situ released and combined with active components with complexing ability and copper ions oxidized in the Fenton system constructed by calcium peroxide to form stable water-soluble copper chloride complexes, realizing the cascade reaction from directional activation to efficient dissolution of the solid surface. In addition, the strong oxidizing hydroxyl radicals generated by the Fenton system can deeply degrade the organic pollutants in the system, i.e. the nitrogen-containing small-molecule organic byproducts generated in the electrolysis process of the nitrogen-containing organic salt complex precursor with a specific structure, and the design ingeniously utilizes the residual oxidation capacity of the reaction system to convert end treatment into in-situ degradation in the process.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, specifically to a copper extraction reagent system and a method for recovering copper from waste printed circuit boards. Background Technology

[0002] Currently, the main technologies for recovering copper from waste printed circuit boards include pyrometallurgy and hydrometallurgy. Pyrometallurgy is energy-intensive and easily produces harmful gases and toxic slag, and has been gradually replaced by hydrometallurgy. The core of hydrometallurgy lies in using chemical leaching agents to selectively dissolve metallic copper from a solid matrix into a solution. Current mainstream hydrometallurgical technologies heavily rely on strong inorganic acids (such as sulfuric acid and nitric acid systems) or highly toxic cyanides. These traditional systems have inherent drawbacks: First, they pose high environmental risks, as strong acid systems generate large amounts of acidic wastewater with high treatment costs, and the high toxicity of cyanides poses a serious challenge to operational safety and environmental protection; second, they have poor selectivity, as strong acids co-leach large amounts of impurity metals such as iron, nickel, and zinc while leaching copper, resulting in a complex composition of the leachate, which greatly increases the difficulty and cost of subsequent solution purification and metal separation; third, they consume a large amount of reagents, especially during acid leaching, which requires continuous mechanical stirring and large amounts of reagent addition to maintain the reaction rate, resulting in low overall energy and material efficiency.

[0003] In recent years, emerging technologies such as ionic liquid leaching and Fenton / Fenton-like oxidation have shown promise as alternatives to traditional leaching agents. Ionic liquids are considered green solvents due to their low volatility and designable structure; however, their application in waste printed circuit board treatment is mostly limited to direct dissolution or as auxiliary leaching agents, and the potential secondary pollution risks posed by their bioaccumulation and persistence in water bodies have not been effectively addressed. Conventional Fenton technology often uses homogeneous addition of hydrogen peroxide and ferrous salts, which suffers from problems such as easy decomposition of reagents, low utilization rate, and difficulty in sustaining the reaction process in complex solid waste systems.

[0004] Furthermore, existing technologies largely focus on resource recycling while neglecting the environmental footprint of the entire process. For the leaching agents themselves, especially the residual problem of recalcitrant organic reagents, there is a lack of effective end-of-pipe control measures; often, the pollution is simply transferred from the solid phase to the liquid phase, creating new treatment challenges.

[0005] Therefore, developing a green recycling technology that can selectively recover copper under mild conditions while achieving efficient reagent utilization and minimizing process pollution has become a key technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a copper extraction reagent system and a method for recovering copper from waste printed circuit boards, aiming to solve the problems of low reagent utilization, low leaching efficiency and environmental pollution in existing copper recycling processes.

[0007] In a first aspect, this application provides a copper extraction reagent system comprising a complexing precursor and calcium peroxide; wherein the complexing precursor is 1-ethyl-3-methylimidazole chloride or N-ethylpyridine chloride.

[0008] Secondly, this application provides a method for recovering copper from waste printed circuit boards using a copper extraction reagent system, characterized in that the process using the aforementioned copper extraction reagent system includes the following steps:

[0009] S1. Cut the printed circuit board to obtain the cut sample;

[0010] S2. Add the cut sample into the heap leaching column, and add calcium peroxide at predetermined height intervals;

[0011] S3. Add the complexed precursor to water and adjust to a predetermined pH value to obtain a precursor mixed solution;

[0012] S4. The precursor mixture solution is circulated and rinsed through the heap leaching column from top to bottom, and a three-electrode system is installed in the heap leaching column to electrolyze the leachate to obtain copper-containing precious solution and residual tailings.

[0013] In some embodiments, in step S3, the predetermined pH value is 8.5 to 9.5.

[0014] In some embodiments, in step S2, the mass density of the calcium peroxide is 0.2~1 g / cm³. 2 .

[0015] In some embodiments, in step S3, the concentration of the complex precursor is 0.5~1 mol / L.

[0016] In some embodiments, in step S2, the height of the heap leaching column is 1.2m and the inner diameter is 10cm; the stacking height of the cut samples in the heap leaching column is 1m; and the predetermined interval height is 20cm.

[0017] In some embodiments, in step S4, the drip rate during the cyclic rinsing is 10 L / m. 2 ·h.

[0018] In some embodiments, in step S4, the liquid level of the precursor mixture solution in the heap leaching column is 10 cm; the three-electrode system is located 2 cm above the bottom liquid level of the precursor mixture solution.

[0019] In some embodiments, in step S4, the three-electrode system consists of an anode: a graphite electrode, a cathode: a titanium-based platinum-plated mesh counter electrode, and a dual salt bridge reference electrode.

[0020] In some embodiments, in step S4, the electrolysis voltage is 10~20V and the electrolysis time is 12h.

[0021] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0023] Figure 1 This is a SEM image of a sample of a discarded printed circuit board after 1 hour of reaction in Example 1 of this application.

[0024] Figure 2 This is an XRD pattern of the residual solids after leaching in Example 1 of this application.

[0025] Figure 3 The image shows the XRD pattern of the residual solids in the leaching process of Comparative Example 3 of this application. Detailed Implementation

[0026] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] To address the problems of low reagent utilization, low leaching efficiency, and environmental pollution in existing copper recycling processes, this application provides a copper extraction reagent system and a method for recovering copper from waste printed circuit boards. A novel synergistic copper extraction mechanism using 1-ethyl-3-methylimidazolium chloride or N-ethylpyridine chloride as multifunctional precursors was constructed. First, a novel synergistic copper extraction mechanism involving "adsorption-electrolytic activation-oxidation-complexation" was constructed, utilizing nitrogen-containing organic salt complexing precursors with specific structures. This mechanism begins with the chemisorption of 1-ethyl-3-methylimidazolium chloride or N-ethylpyridine chloride molecules onto the solid copper surface of discarded printed circuit boards, achieving pre-enrichment of the reaction sites. Subsequently, electrolysis precisely triggers the bond breaking of the precursor molecules adsorbed on the copper surface, releasing chloride ions and complexing active components in situ. Simultaneously, the Fenton system constructed from calcium peroxide plays a crucial role in oxidizing zero-valent copper to high-valent copper ions. The newly generated high-valent copper ions rapidly combine with the released chloride ions and active components to form stable water-soluble copper chloride complexes. This process achieves targeted activation from the solid surface to… The highly efficient dissolution tandem reaction not only greatly improves the reaction rate and selectivity, but also fundamentally eliminates the traditional path of relying on the overall dissolution of strong acids. Second, the solid-phase slow-release Fenton system based on the spatially layered arrangement of calcium peroxide creates a unique reaction environment from the inside out and from solid to liquid by embedding calcium peroxide in layers within the material pile. Under the action of moisture and in alkaline conditions, calcium peroxide slowly dissolves and releases hydrogen peroxide. This slow-release process greatly improves the utilization efficiency of the oxidant. At the same time, the iron, zinc and other metal components inherent in the circuit board powder act as in-situ catalysts, which, together with the slowly released hydrogen peroxide, constitute a highly efficient and long-lasting phase-separated Fenton reaction system, realizing the directional and continuous oxidation of metallic copper. Third, it realizes a closed-loop pollution control system integrating "reaction-self-purification" throughout the entire process. Its core lies in embedding the harmless treatment of residual reagents and reaction byproducts into the main process route. After the main copper leaching reaction is completed, the Fenton system, constructed from calcium peroxide and metallic impurities, continues to function. The resulting highly oxidizing hydroxyl radicals are directed to another key reaction: nitrogen-containing small-molecule organic byproducts (such as imidazole derivatives, organic amines, or small-molecule carboxylic acids) generated during the electrolytic bond breaking and chloride ion release process of the main organic pollutant in the deep degradation system—1-ethyl-3-methylimidazolium chloride or N-ethylpyridine chloride. This advanced oxidation process can gradually mineralize potentially persistent organic pollutants into harmless substances such as carbon dioxide, water, and inorganic salts. This design cleverly utilizes the remaining oxidation capacity of the reaction system to transform end-of-pipe treatment into in-situ degradation within the process, thereby achieving self-purification in the closed-loop process and ultimately achieving a balance between efficient resource recovery and environmental friendliness throughout the entire process.

[0029] In a first aspect, this application provides a copper extraction reagent system comprising a complexing precursor and calcium peroxide; wherein the complexing precursor is 1-ethyl-3-methylimidazole chloride or N-ethylpyridine chloride.

[0030] Secondly, this application provides a method for recovering copper from waste printed circuit boards using a copper extraction reagent system, characterized in that the process using the aforementioned copper extraction reagent system includes the following steps:

[0031] S1. Cut the printed circuit board to obtain the cut sample;

[0032] S2. Add the cut sample into the heap leaching column, and add calcium peroxide at predetermined height intervals;

[0033] S3. Add the complexed precursor to water and adjust to a predetermined pH value to obtain a precursor mixed solution;

[0034] S4. The precursor mixture solution is circulated and rinsed through the heap leaching column from top to bottom, and a three-electrode system is installed in the heap leaching column to electrolyze the leachate to obtain copper-containing precious solution and residual tailings.

[0035] Furthermore, in some embodiments, in step S1, the particle size of the cut sample is less than 10 mesh.

[0036] Furthermore, in some embodiments, in step S3, the predetermined pH value is 8.5 to 9.5; the pH adjuster is a sodium hydroxide solution.

[0037] Furthermore, in some embodiments, in step S2, the mass density of the calcium peroxide is 0.2~1 g / cm³. 2 .

[0038] Furthermore, in some embodiments, in step S3, the concentration of the complex precursor is 0.5~1 mol / L.

[0039] Furthermore, in some embodiments, in step S2, the height of the heap leaching column is 1.2m and the inner diameter is 10cm; the stacking height of the cut samples in the heap leaching column is 1m; and the predetermined interval height is 20cm.

[0040] Furthermore, in some embodiments, in step S4, the drip rate during the cyclic rinsing is 10 L / m. 2 ·h.

[0041] Furthermore, in some embodiments, in step S4, the liquid level of the precursor mixture solution in the heap leaching column is 10 cm; the three-electrode system is located 2 cm above the bottom liquid level of the precursor mixture solution.

[0042] Furthermore, in some embodiments, in step S4, the three-electrode system consists of an anode: a graphite electrode, a cathode: a titanium-based platinum-plated mesh counter electrode, and a dual salt bridge reference electrode.

[0043] Furthermore, in some embodiments, in step S4, the electrolysis voltage is 10~20V and the electrolysis time is 12h.

[0044] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0045] Example 1

[0046] Example 1 provides a method for recovering copper from waste printed circuit boards using a copper extraction reagent system, specifically including the following steps:

[0047] (1) Cut the printed circuit board to a particle size of less than 10 mesh to obtain the cut sample;

[0048] (2) Add the cut sample into a heap leaching column with a height of 1.2m and an inner diameter of 10cm, and add 0.5g / cm³ of material at 20cm intervals. 2 The calcium peroxide has a mineral accumulation height of 1m and consists of 5 layers.

[0049] (3) Add sodium hydroxide solution to an aqueous solution of 1-ethyl-3-methylimidazole chloride with a concentration of 0.75 mol / L to adjust the pH value to 9, and obtain a precursor mixed solution;

[0050] (4) The precursor mixture solution is circulated and rinsed from top to bottom on the heap leaching column at a drip rate of 10 L / m. 2 The upper liquid level is 10 cm. A three-electrode system is constructed with a graphite electrode as the anode, a titanium-based platinum-plated mesh counter electrode, and a double salt bridge reference electrode. The system is installed in the heap leaching column 2 cm above the bottom liquid level. The leaching solution is electrolyzed for 12 h at a working potential of 20 V to obtain a copper-containing precious solution and residual tailings.

[0051] The copper content in the residual tailings of each embodiment and comparative example was measured using ICP-OES, and the copper leaching rate η was then calculated as follows:

[0052]

[0053] Where η represents the copper leaching rate, in %; m1 represents the mass of the printed circuit board, in g; β1 represents the grade of the printed circuit board, in g / t; m2 represents the mass of the residual tailings after leaching the printed circuit board, in g; and β2 represents the grade of the solid residue after leaching the printed circuit board, in g / t.

[0054] The main components of the discarded electro-printed circuit board are shown in Table 1.

[0055] Table 1 Main Components of Waste Circuit Boards

[0056]

[0057] Samples of discarded printed circuit boards collected after 1 hour of reaction in Example 1 were analyzed using scanning electron microscopy backscattering analysis, such as... Figure 1 As shown.

[0058] Depend on Figure 1 The formation of copper oxide demonstrates that elemental copper undergoes a complex chemical reaction to form copper oxide, and the imidazole ring fragment of the complex precursor (1-ethyl-3-methylimidazole chloride) can chemically adsorb onto copper oxide. This result fully proves that the core technical advantage of this invention lies in its proposed "adsorption-electrolytic activation-oxidation-complexation" synergistic copper extraction mechanism. This mechanism is universally applicable to nitrogen-containing organic salt complex precursors with specific structures. The key is that these precursor molecules can effectively adsorb onto the surface of copper and be activated under suitable electrolytic conditions, releasing chloride ions and active components, which then form a stable and soluble complex with copper ions generated by oxidation in the Fenton system.

[0059] The residual solids after leaching in Example 1 were pulverized and subjected to XRD analysis, such as... Figure 2 As shown.

[0060] Depend on Figure 2 It can be seen that no copper, iron, or zinc were detected in the residual solids after leaching, proving that the multi-effect agent system described in this invention has a highly efficient copper leaching effect.

[0061] Example 2

[0062] Example 2 provides a method for recovering copper from waste printed circuit boards using a copper extraction agent system. The difference from Example 1 is that in step (3), the complexing precursor is N-ethylpyridine chloride. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0063] The leaching rate of copper in Examples 1 and 2 was tested, and the results are shown in Table 2.

[0064] Table 2. Types of complex precursors and copper leaching rates in Examples 1-2

[0065]

[0066] As shown in Table 1, the multi-effect reagent system described in this invention can achieve a copper leaching rate of up to 98% under the stated process conditions, regardless of whether 1-ethyl-3-methylimidazole chloride or N-ethylpyridine chloride is used as the complexing precursor.

[0067] Examples 3-4 and Comparative Examples 1-3

[0068] Examples 3-4 and Comparative Examples 1-3 each provide a method for recovering copper from waste printed circuit boards using a copper extraction reagent system. The difference between Example 1 and Example 2 is that the pH value is adjusted differently, as shown in Table 3. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0069] Table 3. pH values ​​and copper leaching rates in Examples 1, 3-4 and Comparative Examples 1-3.

[0070]

[0071] As shown in Table 3, the reagent system of this invention maintains an extremely high copper leaching rate (98%) within a relatively narrow and precise weakly alkaline range (pH 8.5–9.5). This range represents the optimal window for achieving the synergistic effect of oxidation and complexation. Once outside this range, the leaching efficiency decreases significantly.

[0072] The core reason for the decrease in leaching rate lies in the transformation of copper ion form and the failure of the key reaction system. Under low pH conditions (Comparative Example 1, pH 8.32), the system lacks hydroxide ions, which severely hinders the construction of the Fenton reaction system. Calcium peroxide decomposes rapidly and releases oxygen, failing to stably and continuously provide hydrogen peroxide, which is the core of the Fenton reaction. This leads to a sharp decrease in the efficiency of the Fenton reaction, resulting in a decrease in the copper leaching rate to 89%. Under strongly alkaline conditions, the high-valence copper ions generated by the limited Fenton reaction in the system quickly combine with hydroxide ions in the water to form copper hydroxide precipitate. This precipitate coats the surface of unreacted copper particles, severely hindering subsequent oxidation and complexation reactions. It also isolates the copper from contact with chloride ions and active complexing components, forcibly terminating the dissolution process and causing a sharp decrease in the leaching rate.

[0073] The residual solids from the leaching process in Comparative Example 3 were pulverized and subjected to XRD analysis, such as... Figure 3 As shown.

[0074] pass Figure 3 The XRD pattern revealed that the reaction in Comparative Example 3 was too alkaline, resulting in the formation of copper hydroxide.

[0075] Examples 5-6 and Comparative Examples 4-5

[0076] Examples 5-6 and Comparative Examples 4-5 respectively provide a method for recovering copper from waste printed circuit boards using a copper extraction reagent system. The difference between Example 1 and Example 2 is that the electrolysis voltage is different, as shown in Table 4. The other steps are roughly the same as in Example 1 and will not be described again here.

[0077] Table 4 shows the electrolysis voltage and copper leaching rate in Examples 1, 5-6, and Comparative Examples 4-5.

[0078]

[0079] As shown in Table 4, the electrolytic activation step employed in this invention has a clear and optimal working potential window. When the working potential is controlled within the range of 10~20V, the copper leaching rate can be maintained at a high level of over 96%, indicating that within this potential range, electrolysis can most effectively synergize with the chemical leaching system. When the working potential is too low, the applied electric field strength is insufficient to effectively drive the directional adsorption and bond breaking reaction of 1-ethyl-3-methylimidazole chloride on the copper surface, resulting in a severe deficiency in the release of chloride ions and active complex components. Without this crucial "electrolytic activation" step, even if the Fenton system can partially oxidize copper, subsequent efficient complexation and dissolution cannot be achieved, resulting in a leaching rate of only 38%. Within the 10~20V range, the electric field strength is just sufficient to efficiently induce bond breaking of the complex precursor molecules adsorbed on the copper surface, releasing sufficient chloride ions and active complex components in situ. These components then rapidly form soluble complexes with the copper ions generated by the Fenton system oxidation, achieving perfect synergy and cycle in the "oxidation-complexation" process.

[0080] Examples 7-8 and Comparative Examples 6-8

[0081] Examples 7-8 and Comparative Examples 6-8 each provide a method for recovering copper from waste printed circuit boards using a copper extraction reagent system. The difference from Example 1 is that the concentration of 1-ethyl-3-methylimidazole chloride is different, as shown in Table 5. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0082] Table 5. Concentration of 1-ethyl-3-methylimidazolium chloride and leaching rate of copper in Examples 1, 7-8 and Comparative Examples 6-8.

[0083]

[0084] As shown in Table 5, the technical solution of this invention maintains excellent copper leaching rates (95-98%) across a wide range of complexing precursor concentrations (0.5-1 mol / L), demonstrating good operational flexibility. However, when the concentration is too low (Comparative Example 8, 0.4 mol / L), the leaching rate drops significantly to 85% because sufficient adsorption and adequate chloride ions and complexing components cannot be formed on the copper surface. It should be noted that although the copper leaching rate can still be maintained at 98% at concentrations as high as 1.15 mol / L and even 3 mol / L, these ultra-high concentrations will cause two major problems. First, the economic cost increases significantly: the complexing precursor (1-ethyl-3-methylimidazole chloride) is the main reagent, and its cost accounts for a significant proportion of the overall process economy. Increasing the concentration to above 1 mol / L, especially to 3 mol / L, will lead to a significant increase in reagent consumption and raw material costs. The rapid increase in concentration, while seemingly uneconomical for industrial applications, fails to further enhance leaching efficiency. Secondly, the excessively high concentration severely hinders the system's self-purification function: the excessive complexing precursor far exceeds the oxidation capacity that the Fenton reaction can provide within a given time. This results in a large amount of undecomposed 1-ethyl-3-methylimidazole chloride and its degradation intermediates remaining in the solution after the copper extraction reaction. These residual organic substances not only cause secondary pollution, but more importantly, they severely consume reactive oxygen species (such as hydroxyl radicals) in the system, competitively inhibiting the deep oxidative degradation of the target pollutants, thereby completely destroying the integrated closed loop of "reaction-self-purification" designed in this invention.

[0085] Therefore, considering leaching efficiency, process economy, and environmental friendliness, optimizing the concentration of the complexing precursor between 0.5 and 1 mol / L is the optimal choice. This concentration range ensures efficient copper leaching, controls reagent costs, and guarantees the smooth completion of the subsequent self-purification process, demonstrating the comprehensive advantages of this invention in terms of both technical efficiency and green process.

[0086] Examples 9-10 and Comparative Examples 9-10

[0087] Examples 9-10 and Comparative Examples 9-10 respectively provide a method for recovering copper from waste printed circuit boards using a copper extraction reagent system. The difference between Example 1 and Example 2 is that the mass density of the added calcium peroxide is different, as shown in Table 6. The other steps are roughly the same as in Example 1 and will not be described again here.

[0088] Table 6 shows the mass density of calcium peroxide and the copper leaching rate in Examples 1, 9-10 and Comparative Examples 9-10.

[0089]

[0090] As shown in Table 6, the dosage of calcium peroxide is crucial to the normal operation of this technology system. Without the addition of calcium peroxide, the copper leaching rate is only 52%, demonstrating that the lack of a slow-release Fenton system constructed from calcium peroxide is a key factor in the failure of this technology. Without a continuous supply of hydrogen peroxide, the system cannot effectively oxidize zero-valent copper into complexable copper ions, leading to the failure of the leaching reaction. When the dosage is increased to 0.1 g / cm³, the leaching rate improves significantly. 2 At this point, the leaching rate rose to 87%, indicating that an oxidation environment had been partially established. However, due to insufficient total oxidant, the oxidation efficiency was limited, and complete copper leaching could not be achieved. It is worth noting that when the mass density of calcium peroxide reached 0.2 g / cm³... 2 At these levels, the system can maintain a high leaching rate of 95-98%, indicating the existence of a minimum effective threshold (approximately 0.2 g / cm³). 2 As long as this threshold is exceeded, the reagent requirements for the "oxidation-complexation" cycle can be met; however, when the amount of calcium peroxide added is too high, although the leaching rate is still very high, it will bring significant negative economic effects.

[0091] In summary, this application provides a method for recovering copper from waste printed circuit boards using a copper extraction reagent system. A novel synergistic copper extraction mechanism using 1-ethyl-3-methylimidazole chloride or N-ethylpyridine chloride as multifunctional precursors was constructed. First, a novel "adsorption-electrolytic activation-oxidation-complexation" synergistic copper extraction mechanism using nitrogen-containing organic salt complexing precursors with specific structures was constructed. This mechanism begins with the chemical adsorption of 1-ethyl-3-methylimidazole chloride or N-ethylpyridine chloride molecules onto the solid copper surface of waste printed circuit boards, achieving pre-enrichment of reaction sites. Subsequently, by applying electrolysis, the precursor molecules adsorbed on the copper surface are precisely triggered to break bonds, releasing chloride ions and complexing active components in situ. Simultaneously, the Fenton system constructed from calcium peroxide plays a crucial role in oxidizing zero-valent copper to high-valent copper ions. The newly generated high-valent copper ions rapidly combine with the released chloride ions and active components to form a stable water-soluble copper chloride complex. This process achieves directional activation from the solid surface to… The highly efficient dissolution tandem reaction not only greatly improves the reaction rate and selectivity, but also fundamentally eliminates the traditional path of relying on the overall dissolution of strong acids. Second, the solid-phase slow-release Fenton system based on the spatially layered arrangement of calcium peroxide creates a unique reaction environment from the inside out and from solid to liquid by embedding calcium peroxide in layers within the material pile. Under the action of moisture and in alkaline conditions, calcium peroxide slowly dissolves and releases hydrogen peroxide. This slow-release process greatly improves the utilization efficiency of the oxidant. At the same time, the iron, zinc and other metal components inherent in the circuit board powder act as in-situ catalysts, which, together with the slowly released hydrogen peroxide, constitute a highly efficient and long-lasting phase-separated Fenton reaction system, realizing the directional and continuous oxidation of metallic copper. Third, it realizes a closed-loop pollution control system integrating "reaction-self-purification" throughout the entire process. Its core lies in embedding the harmless treatment of residual reagents and reaction byproducts into the main process route. After the main copper leaching reaction is completed, the Fenton system, constructed from calcium peroxide and metallic impurities, continues to function. The resulting highly oxidizing hydroxyl radicals are directed to another key reaction: nitrogen-containing small-molecule organic byproducts (such as imidazole derivatives, organic amines, or small-molecule carboxylic acids) generated during the electrolytic bond breaking and chloride ion release process of the main organic pollutant in the deep degradation system—1-ethyl-3-methylimidazolium chloride or N-ethylpyridine chloride. This advanced oxidation process can gradually mineralize potentially persistent organic pollutants into harmless substances such as carbon dioxide, water, and inorganic salts. This design cleverly utilizes the remaining oxidation capacity of the reaction system to transform end-of-pipe treatment into in-situ degradation within the process, thereby achieving self-purification in the closed-loop process and ultimately achieving a balance between efficient resource recovery and environmental friendliness throughout the entire process.

[0092] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for recovering copper from waste printed circuit boards using a copper extraction reagent system, characterized by, The copper extraction reagent system comprises a complexing precursor and calcium peroxide; wherein the complexing precursor is 1-ethyl-3-methylimidazole chloride or N-ethylpyridine chloride; The method comprises the following steps: S1. Cutting a printed circuit board to obtain a cut sample; S2. Adding the cut sample into a heap leaching column, and adding calcium peroxide at every interval predetermined height; S3. Adding the complexing precursor into water, and adjusting to a predetermined pH value to obtain a precursor mixed solution; the predetermined pH value is 8.5-9.5; S4. Circulating leaching the heap leaching column from top to bottom with the precursor mixed solution, and installing a three-electrode system in the heap leaching column to electrolyze the leaching solution to obtain a copper-containing noble liquid and residual tailings.

2. The method for recovering copper from waste printed circuit boards using a copper extraction reagent system according to claim 1, characterized in that, In step S2, the mass density of the calcium peroxide is 0.2-1 g / cm 2 .

3. The method for recovering copper from waste printed circuit boards using a copper extraction reagent system according to claim 1, characterized in that, In step S3, the concentration of the complexing precursor is 0.5-1 mol / L.

4. The method for recovering copper from waste printed circuit boards using a copper extraction reagent system according to claim 1, characterized in that, In step S2, the height of the heap leaching column is 1.2 m, and the inner diameter is 10 cm; the cut sample in the heap leaching column has a stacking height of 1 m; and the interval predetermined height is 20 cm.

5. The method for recovering copper from waste printed circuit boards using a copper extraction reagent system according to claim 1, characterized in that, In step S4, the intensity of the drip irrigation is 10 L / m 2 • h.

6. The method for recovering copper from waste printed circuit boards by using a copper extraction reagent system according to claim 1, characterized in that, In step S4, the liquid level height of the precursor mixed solution in the heap leaching column is 10 cm; and the three-electrode system is located 2 cm above the bottom liquid level of the precursor mixed solution.

7. The method for recovering copper from waste printed circuit boards by using a copper extraction reagent system according to claim 1, characterized in that, In step S4, the three-electrode system is an anode: graphite electrode, a cathode: titanium-based platinum-coated mesh-shaped counter electrode, and a double-salt bridge reference electrode.

8. The method for recovering copper from waste printed circuit boards using a copper extraction reagent system according to claim 1, characterized in that, In step S4, the voltage of the electrolysis is 10-20 V, and the electrolysis time is 12 h.

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