Amino acid complexing agent system and method of treating electronic waste to produce high purity glycine copper

Abstract

The application provides an amino acid composite reagent system and a method for treating electronic waste to prepare high-purity glycine copper, and belongs to the technical field of metal hydrometallurgy and resource recycling. The application builds an ammonia catalytic reduction mechanism by designing an amino acid composite reagent system, greatly improves the leaching rate, simultaneously inhibits the dual effects of copper hydroxide precipitation and glycine chelation, and realizes efficient solution of copper ions; through narrow window regulation technology of pH at 9.5±0.2, the stability of ammonia, the activity of glycine anion are maintained, and the selective leaching rate of copper is ensured; a directional crystallization process of leaching solution is constructed, the "self-assembly directional crystallization" process of glycine copper chelate is used, based on the saturation concentration of glycine copper in the leaching solution and the stable chelate structure, through three-stage crystallization precise regulation, the preparation of high-purity crystal is realized. The process realizes the closed-loop crystallization system of "zero addition of crystal seeds and zero wastewater discharge" of the copper-containing complex leaching solution of electronic waste.

Description

Technical Field

[0001] This invention relates to the fields of hydrometallurgical processes and renewable resources, specifically to an amino acid composite reagent system and a method for preparing high-purity copper glycine from electronic waste. Background Technology

[0002] With global annual e-waste production exceeding 53.6 million tons and continuing to surge, despite the abundance of metal resources in e-waste (such as copper and rare precious metals accounting for 7% of PCB mass), existing recycling technologies struggle to balance efficient extraction with pollution control.

[0003] Current mainstream recycling relies on pyrometallurgical processes (accounting for over 70% of printed circuit board (PCB) processing), which suffers from drawbacks such as high energy consumption, severe air pollution, and low metal recovery rates. While hydrometallurgical processes have shown some improvement, the use of highly toxic agents like cyanide violates green principles and faces the challenge of multi-metal co-leaching: PCBs contain over 40 metals, and traditional leaching agents have poor selectivity, resulting in the simultaneous leaching of copper along with precious metals (gold, silver, etc.) and impurity metals (iron, nickel, etc.), leading to a surge in subsequent separation costs. In particular, copper, as the most abundant valuable metal in PCBs, still lacks a clean and efficient solution for its targeted recycling and high-value conversion.

[0004] Currently, while the glycine system has green potential in the field of metal resource recovery, existing research suffers from three major drawbacks: (1) glycine alone has a low metal leaching rate; (2) the multi-metal competition mechanism is unclear, making it impossible to precisely control the selective leaching of copper; and (3) the leaching solution has a complex composition, making it difficult to separate the target metal and directly prepare high-purity products. This results in low resource conversion efficiency and residual heavy metals and organic matter in the wastewater after the reaction, posing a risk of secondary pollution. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides an amino acid composite reagent system and a method for preparing high-purity copper glycine from electronic waste, aiming to solve the problems of low leaching efficiency, inability to selectively leach, difficulty in separating and preparing high-purity products, and serious pollution of copper and high-purity copper glycine from electronic waste by existing reagent systems.

[0006] In a first aspect, this application provides an amino acid composite drug system, which comprises an amino acid chelating agent, an amine auxiliary agent, and a hydrogen peroxide solution; the amino acid chelating agent comprises glycine or dipeptides and polypeptides containing glycine structural fragments, and the amine auxiliary agent comprises at least one of ammonia, ammonium chloride, and propylenediamine.

[0007] In the technical solution of this application embodiment, by designing an amino acid composite agent system, an ammonia catalytic barrier reduction mechanism is constructed to reduce the oxidation energy barrier of copper(O) to copper(II), thereby increasing the leaching rate by more than 50%, and simultaneously inhibiting the dual effects of copper hydroxide precipitation and glycine chelation, thus achieving efficient dissolution and storage of copper ions.

[0008] In some embodiments, the mass concentration of the amino acid chelating agent is 20-40 g / L, the molar concentration of the amine auxiliary agent is 22-88 mmol / L, and the concentration of the hydrogen peroxide solution is 10-90 ml / L.

[0009] In this embodiment, the specific proportions of each component in the drug result in a better synergistic effect between the components.

[0010] Secondly, this application provides a method for preparing high-purity copper glycine from electronic waste using an amino acid composite reagent system. The method comprises the following steps:

[0011] S1. Crush the electronic waste to obtain the crushed sample;

[0012] S2. Add water to the crushed sample and stir to obtain a slurry;

[0013] S3. Add an amino acid composite reagent system to the slurry, then adjust the pH value, stir and leach, and then separate the solid and liquid to obtain the leachate;

[0014] S4. Perform targeted impurity removal pretreatment on the leachate to obtain a pretreated leachate;

[0015] S5. Place the pretreated leachate at the center of a Helmholtz coil, connect the current and calibrate the magnetic field strength at the center point to perform the first evaporation, and monitor the Raman spectrum of the crystal at 518 cm⁻¹ in real time during evaporation. -1 The peak intensity is maintained until the nucleation is complete, then a second evaporation is performed, followed by a third evaporation, to obtain highly crystalline copper glycine crystals.

[0016] In the technical solution of this application embodiment, during the leaching process of electronic waste, a narrow window control technology of pH at 9.5±0.2 is used to simultaneously maintain ammonia stability and glycine anion activity within this critical range, ensuring the selective leaching rate of copper. In addition, a directional crystallization process for the leachate is constructed, utilizing the "self-assembly directional crystallization" process of glycine copper chelate. Based on the saturated concentration of glycine copper and the stable chelate structure in the leachate, high-purity crystals are prepared in one step through precise control of three-stage crystallization: under the critical window of pH at 9.5±0.2 and low-temperature evaporation conditions of 30℃, the self-assembly growth of [Cu(Gly)2] molecules along the (001) crystal plane is triggered, forming needle-like crystals with an aspect ratio >10 (SEM verification shows a size of 5~30μm). At the same time, magnetic field-assisted crystallization induces the [Cu(Gly)2] molecules to oriented along the crystal plane, inhibiting impurity eutectic. Simultaneously, the ammonia synergistic control mechanism is used to deeply inhibit impurity eutectic (Fe 2+ / Pb 2+ The residual concentration is <50ppm), and the crystal purity is >98.0%, meeting industrial-grade standards. This technology eliminates three energy-intensive purification processes: extraction, back-extraction, and electrolysis. The mother liquor is recycled through amino acid regeneration, achieving a closed-loop crystallization system with "zero seed crystal addition and zero wastewater discharge" for complex copper-containing leaching solutions from electronic waste.

[0017] In some embodiments, in step S3, the pH adjustment agent is sodium hydroxide, and the pH value is 9.3~9.7.

[0018] In this embodiment, within the critical pH range, the stability of ammonia and the activity of glycine anions can be maintained simultaneously during the leaching process, ensuring the selective leaching rate of copper.

[0019] In some embodiments, in step S5, during the first evaporation, the evaporation temperature is 49.8~50.2℃, and when the nucleation induction is completed, the Raman spectrum is at 518 cm⁻¹. -1 The peak intensity has a refractive index of 1.385; in the second evaporation, the evaporation temperature is 39.8~40.2℃ and the evaporation time is 120min; the third evaporation step is: cooling to 24.8~25.2℃ at a rate of 0.2℃ / min, and then evaporating for 24h.

[0020] In this embodiment, a leachate directional crystallization process is constructed. The "self-assembly directional crystallization" process of glycine copper chelate is used. Based on the saturated concentration of glycine copper in the leachate and the stable chelate structure, high-purity crystals are prepared in one step through precise control of three-stage crystallization.

[0021] In some embodiments, the relative humidity of the evaporation in the third evaporation is 30%.

[0022] In this embodiment, evaporation is carried out in an environment with a relative humidity of 30% to avoid the formation of crystal surface defects.

[0023] In some embodiments, in step S5, the current is 6.25A and the magnetic field strength at the center point is 0.50±0.01T.

[0024] In this embodiment, the magnetic field can assist crystallization, induce [Cu(Gly)2] molecules to align along the crystal plane, and suppress impurity eutectic.

[0025] In some embodiments, step S4, the targeted impurity removal pretreatment includes the following steps:

[0026] NH4+ with a mass concentration of 2 g / L was added to the leachate. + -ZSM-5 zeolite, at room temperature, magnetically stirred at 300 rpm for 30 minutes, then filtered.

[0027] In this embodiment, the leachate is targeted for impurity removal through the above-described operation.

[0028] In some embodiments, the stirring leaching time in step S3 is 24~48h.

[0029] In this embodiment, stirring ensures that the reagent comes into full contact with the metal waste, resulting in more complete leaching.

[0030] In some embodiments, in step S1, the particle size of the crushed sample is less than 50 mesh.

[0031] In this embodiment, electronic waste is crushed to a specific particle size to facilitate subsequent leaching treatment.

[0032] In some embodiments, in step S2, the concentration of the slurry is 1-5%.

[0033] 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

[0034] 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.

[0035] Figure 1The images shown are physical images and performance characterization diagrams of the copper glycine crystals prepared in the embodiments of this application; wherein (a) is a physical image of the copper glycine crystal, (b) is an XRD pattern of the copper glycine crystal, (c) is a backscattered SEM image of the copper glycine crystal, and (d) is a SEM image of the copper glycine crystal.

[0036] Figure 2 These are performance characterization diagrams of waste printed circuit board powder samples before and after leaching in the embodiments of this application; wherein (a) is a cross-sectional backscattered SEM image of the waste printed circuit board powder sample, (b) is a SEM image of the waste printed circuit board powder sample after leaching, and (c) is a magnified SEM image and energy dispersive spectroscopy analysis diagram of the waste printed circuit board powder sample after leaching. Detailed Implementation

[0037] 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.

[0038] 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.

[0039] To address the problems of low leaching efficiency, lack of selective leaching, difficulty in separating and preparing high-purity products, and severe pollution associated with existing amino acid composite reagent systems for copper and high-purity glycine copper from electronic waste, this application provides an amino acid composite reagent system and a method for treating electronic waste to prepare high-purity glycine copper. By designing the amino acid composite reagent system and constructing an ammonia catalytic barrier lowering mechanism, the oxidation energy barrier for the conversion of copper(O) to copper(II) is reduced, increasing the leaching rate by more than 50%. Simultaneously, the dual effects of copper hydroxide precipitation and glycine chelation are inhibited, achieving efficient copper ion dissolution. During the electronic waste leaching process, a narrow-window pH control technology at 9.5±0.2 is used to simultaneously maintain ammonia stability and glycine anion activity within this critical range, ensuring the selective leaching rate of copper. Furthermore, the self-purification properties of the leachate are utilized to induce in-situ crystallization of the glycine-copper complex, directly preparing chemical-grade glycine copper products. A directional crystallization process for leachate was constructed, utilizing the "self-assembly directional crystallization" process of glycine copper chelate. Based on the saturated concentration and stable chelate structure of glycine copper in the leachate, high-purity crystals were prepared in one step through precise control of three-stage crystallization: Under the critical window of pH 9.5±0.2 and low-temperature evaporation conditions of 30℃, the self-assembly growth of [Cu(Gly)2] molecules along the (001) crystal plane was triggered, forming needle-like crystals with an aspect ratio >10 (SEM verification showed a size of 5~30μm). Simultaneously, magnetic field-assisted crystallization induced the directional alignment of [Cu(Gly)2] molecules along the crystal plane, inhibiting impurity eutectic; at the same time, the ammonia synergistic regulation mechanism was used to deeply inhibit impurity eutectic (Fe 2+ / Pb 2+ The residual concentration is <50ppm), and the crystal purity is >98.0%, meeting industrial-grade standards. This technology eliminates three energy-intensive purification processes: extraction, back-extraction, and electrolysis. The mother liquor is recycled through amino acid regeneration, achieving a closed-loop crystallization system with "zero seed crystal addition and zero wastewater discharge" for complex copper-containing leaching solutions from electronic waste.

[0040] Firstly, an amino acid complex drug system, comprising an amino acid chelating agent, an amine auxiliary agent, and a hydrogen peroxide solution; wherein the amino acid chelating agent comprises glycine or dipeptides and polypeptides containing glycine structural fragments, and the amine auxiliary agent comprises at least one of ammonia, ammonium chloride, and propylenediamine.

[0041] In the technical solution of this application embodiment, by designing an amino acid composite agent system, an ammonia catalytic barrier reduction mechanism is constructed to reduce the oxidation energy barrier of copper(O) to copper(II), thereby increasing the leaching rate by more than 50%, and simultaneously inhibiting the dual effects of copper hydroxide precipitation and glycine chelation, thus achieving efficient dissolution and storage of copper ions.

[0042] Furthermore, in some embodiments, the mass concentration of the amino acid chelating agent is 20-40 g / L, the molar concentration of the amine auxiliary agent is 22-88 mmol / L, and the concentration of the hydrogen peroxide solution is 10-90 ml / L.

[0043] In the technical solution of this application embodiment, the specific proportions of each component in the agent result in a better synergistic effect between the components.

[0044] Secondly, this application provides a method for preparing high-purity copper glycine from electronic waste using an amino acid composite reagent system. The method comprises the following steps:

[0045] S1. Crush the electronic waste to obtain the crushed sample;

[0046] S2. Add water to the crushed sample and stir to obtain a slurry;

[0047] S3. Add an amino acid composite reagent system to the slurry, then adjust the pH value, stir and leach, and then separate the solid and liquid to obtain the leachate;

[0048] S4. Perform targeted impurity removal pretreatment on the leachate to obtain a pretreated leachate;

[0049] S5. Place the pretreated leachate at the center of a Helmholtz coil, connect the current and calibrate the magnetic field strength at the center point to perform the first evaporation, and monitor the Raman spectrum of the crystal at 518 cm⁻¹ in real time during evaporation. -1 The peak intensity is maintained until the nucleation is complete, then a second evaporation is performed, followed by a third evaporation, to obtain highly crystalline copper glycine crystals.

[0050] In the technical solution of this application embodiment, during the leaching process of electronic waste, a narrow window control technology of pH at 9.5±0.2 is used to simultaneously maintain the stability of ammonia and the activity of glycine anions within this critical range, ensuring selective leaching of copper. In addition, a directional crystallization process for the leachate is constructed, utilizing the "self-assembly directional crystallization" process of glycine copper chelate. Based on the saturated concentration of glycine copper and the stable chelate structure in the leachate, high-purity crystals are prepared in one step through precise control of three-stage crystallization: under the critical window of pH at 9.5±0.2 and low-temperature evaporation conditions of 30℃, the self-assembly growth of [Cu(Gly)2] molecules along the (001) crystal plane is triggered, forming needle-like crystals with an aspect ratio >10 (SEM verification shows a size of 5~30μm). At the same time, magnetic field-assisted crystallization is used to induce the directional alignment of [Cu(Gly)2] molecules along the crystal plane, inhibiting impurity eutectic. Simultaneously, the ammonia synergistic control mechanism is used to deeply inhibit impurity eutectic (Fe 2+ / Pb 2+The residual concentration is <50ppm), and the crystal purity is >98.0%, meeting industrial-grade standards. This technology eliminates three energy-intensive purification processes: extraction, back-extraction, and electrolysis. The mother liquor is recycled through amino acid regeneration, achieving a closed-loop crystallization system with "zero seed crystal addition and zero wastewater discharge" for complex copper-containing leaching solutions from electronic waste.

[0051] Furthermore, in some embodiments, in step S3, the pH adjustment agent is sodium hydroxide, and the pH value is 9.3~9.7.

[0052] In the technical solution of this application embodiment, the ammonia stability and glycine anion activity can be maintained simultaneously within the critical pH range, ensuring selective copper leaching.

[0053] Furthermore, in some embodiments, in step S5, during the first evaporation, the evaporation temperature is 49.8~50.2℃, and when the crystal nucleation induction is completed, the Raman spectrum is at 518 cm⁻¹. -1 The peak intensity has a refractive index of 1.385; in the second evaporation, the evaporation temperature is 39.8~40.2℃ and the evaporation time is 120min; the third evaporation step is: cooling to 24.8~25.2℃ at a rate of 0.2℃ / min, and then evaporating for 24h.

[0054] In the technical solution of this application embodiment, a leachate directional crystallization process is constructed. The "self-assembly directional crystallization" process of glycine copper chelate is used. Based on the saturated concentration of glycine copper in the leachate and the stable chelate structure, high-purity crystals are prepared in one step through precise control of three-stage crystallization.

[0055] Furthermore, in some embodiments, the relative humidity of the evaporation in the third evaporation is 30%.

[0056] In the technical solution of this application embodiment, evaporation is carried out in an environment with a relative humidity of 30% to avoid the formation of crystal surface defects.

[0057] Furthermore, in some embodiments, in step S5, the current is 6.25A and the magnetic field strength at the center point is 0.50±0.01T.

[0058] In the technical solution of this application embodiment, the magnetic field can assist crystallization, induce [Cu(Gly)2] molecules to align along the crystal plane, and suppress impurity eutectic.

[0059] Furthermore, in some embodiments, step S4, the targeted impurity removal pretreatment includes the following steps:

[0060] NH4+ with a mass concentration of 2 g / L was added to the leachate. +-ZSM-5 zeolite, at room temperature, magnetically stirred at 300 rpm for 30 minutes, then filtered.

[0061] In the technical solution of this application embodiment, the leachate is targeted to remove impurities through the above-described operation.

[0062] Furthermore, in some embodiments, in step S3, the stirring leaching time is 24~48h.

[0063] In the technical solution of this application embodiment, stirring allows the agent to come into full contact with the metal waste, resulting in more complete leaching.

[0064] Furthermore, in some embodiments, in step S1, the particle size of the crushed sample is less than 50 mesh.

[0065] In the technical solution of this application embodiment, electronic waste is crushed to a specific particle size to facilitate subsequent leaching treatment.

[0066] Furthermore, in some embodiments, in step S2, the concentration of the slurry is 1-5%.

[0067] 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.

[0068] Example 1

[0069] Example 1 provides an amino acid composite drug system comprising glycine, ammonium chloride, and hydrogen peroxide solution.

[0070] The method for preparing high-purity copper glycine from electronic waste using the above-mentioned amino acid composite reagent system specifically includes the following steps:

[0071] (1) The waste printed circuit board was crushed to a particle size of less than 50 mesh to obtain a crushed sample. Water was added to the crushed sample and stirred to obtain a slurry with a concentration of 2%.

[0072] (2) Add an amino acid composite reagent system to the above slurry, wherein glycine is 30 g / L, ammonium chloride is 66 mmol / L, hydrogen peroxide solution is 50 ml / L, and then add sodium hydroxide to adjust the pH to 9.5; stir for 36 h, leach copper, and then filter to obtain leachate;

[0073] (3) Add 2.0 g of NH4 to 1 L of leachate. +-ZSM-5 zeolite. Magnetic stirring was set to 300 rpm and stirred for 30 minutes at room temperature. The solution was then filtered through quantitative filter paper to obtain the pretreated leachate.

[0074] (4) Place the pretreated leachate at the center of a Helmholtz coil. Set the DC current through the Helmholtz coil to 6.25A and calibrate the magnetic field strength at the center of the crystallizer to 0.5T using a gaussmeter. Evaporate at 50℃ and monitor the Raman spectrum of the crystals during evaporation in real time. When the Raman spectrum reaches 518 cm⁻¹... -1 When the peak intensity reaches a refractive index of 1.385, the crystal nucleation is completed. The temperature is then adjusted to 40℃ and evaporated for 120 min. Next, the temperature is gradually reduced from 40℃ to 25℃ at a rate of 0.2℃ / min. Evaporation is carried out for 24 h in an environment with a relative humidity of 30% to obtain highly crystalline copper glycine crystals.

[0075] A physical image of the glycine copper crystals prepared in this embodiment is shown below. Figure 1 As shown in (a), the XRD pattern of copper glycine crystals is as follows: Figure 1 As shown in (b), the backscattered SEM image of the copper glycine crystal is as follows: Figure 1 As shown in (c), the SEM image of the copper glycine crystal is as follows. Figure 1 As shown in (d).

[0076] from Figure 1 As can be seen, the precipitated copper products are mostly needle-like structures with smooth surfaces and a size of approximately 5–30 μm. Based on the comparison of the test results in the XRD pattern, its characteristic peaks are consistent with the diffraction card Cu(Gly)2 (PDF#00-052-2022) in the ICDD powder diffraction database. Specifically, the diffraction peaks at 15.7°, 18.1°, 22.3°, 23.8°, 24.9°, and 31.4° belong to the (111), (220), (221), (311), (002), and (312) crystal planes identified in the diffraction card Cu(Gly)2 (PDF#00-052-2022), respectively. The absence of characteristic peaks for Cu(OH)₂ (PDF#80-0656) and NaOH (PDF#74-1120) indicates that the main component of the precipitate from the leaching solution through evaporation and crystallization is glycine-copper, and the impurities in the crystals are not sodium hydroxide. This also suggests that glycine coordinates with copper ions during leaching, forming a stable glycine-copper complex, and the optimized amino acid composite reagent system inhibits the formation of copper hydroxide.

[0077] Examples 2-3 and Comparative Examples 1-2

[0078] Examples 2-3 and Comparative Examples 1-2 respectively provide a method for preparing high-purity copper glycine from electronic waste using an amino acid composite reagent system. The difference from Example 1 is that the amount of glycine used is different, as shown in Table 1. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0079] The leaching rate of copper in the leachate of step (2) in Examples 1-3 and Comparative Examples 1-2, and the yield and purity of copper glycine in step (5) were measured respectively. The results are shown in Table 1.

[0080] Table 1. Glycine dosage and copper leaching effect in Examples 1-3 and Comparative Examples 1-2, and their product indicators.

[0081]

[0082] Table 1 shows that the glycine concentration significantly affects the copper recovery efficiency and product purity. When the glycine concentration is 30 g / L (Example 1), the copper leaching rate reaches 95.7%, and the glycine-copper purity is 99.2%, with a yield of 87.5%. Too low a concentration (10 g / L, Comparative Example 1) causes the leaching rate to plummet to 69.2%, with a yield of only 38.8%. Too high a concentration (50 g / L, Comparative Example 2), while increasing the yield to 94.7%, causes impurities to co-crystallize, resulting in a sharp drop in purity to 68.4%. This indicates that when the glycine concentration is in the range of 20-40 g / L, both copper recovery efficiency and product purity are good, combined with NH4+. + -ZSM-5 zeolite impurity removal and 0.5T magnetic field-assisted gradient crystallization process have enabled the efficient recovery of copper from electronic waste and the green preparation of high-purity copper glycine.

[0083] Comparative Examples 3-6

[0084] Comparative Example 3 provides a method for preparing high-purity copper glycine from electronic waste using an amino acid composite agent system. The difference between this method and Example 1 is that the types of amino acid chelating agents are different, as shown in Table 2. The rest is roughly the same as Example 1 and will not be repeated here.

[0085] Table 2. Types of amino acid chelating agents, copper leaching effects, and product indicators in Examples 1 and Comparative Examples 3-6

[0086]

[0087] Table 2 shows that glycine exhibits the best overall performance as a chelating agent in copper leaching systems containing oxidants (such as H2O2). Its leaching rate (95.7%), product yield (87.5%), and purity (99.2%) are all significantly higher than those of other peptide chelating agents. The fundamental reason is that peptides (such as glutathione and glycyl-alanine) undergo peptide bond cleavage under H2O2 / heavy metal conditions, producing small glycine fragments that chelate copper ions. However, this process also increases impurities in byproducts (other amino acid fragments from peptide bond cleavage), reducing purity to 60-77%. In contrast, aspartic phenylalanine methyl ester has the lowest leaching rate (52.9%) due to ester bonds and hydrophobic benzene rings hindering coordination.

[0088] Examples 4-5 and Comparative Examples 7-9

[0089] Examples 4-5 and Comparative Examples 7-9 respectively provide a method for preparing high-purity copper glycine from electronic waste using an amino acid composite reagent system. The difference from Example 1 is that the molar concentration of ammonium chloride is different, as shown in Table 3. The rest is roughly the same as Example 1 and will not be repeated here.

[0090] Table 3. The molar concentration of ammonium chloride, copper leaching effect, and product indicators in Examples 1, 4-5, and Comparative Examples 7-9.

[0091]

[0092] Table 3 shows that ammonium chloride concentration has a significant regulatory effect on the synthesis of copper glycine. Without ammonium chloride (Comparative Example 7), the copper leaching rate (69.9%), yield (60.5%), and purity (65.8%) all decreased significantly, proving that NH4+... + It is a key auxiliary agent for maintaining efficient chelation (possibly through the formation of [Cu(NH3)]). n ] 2+ (Intermediate promotes copper activation). Within the ammonium chloride concentration range of 22–88 mmol / L: leaching rate (93.7–95.9%) and purity (99.0–99.2%) remained stable, while yield increased with concentration (from 82.1% to 90.0%). When the ammonium chloride concentration reached 100 mmol / L (Comparative Example 9), although the leaching rate (95.9%) and yield (92.8%) were highest, the purity plummeted to 47.9%, indicating excess NH4. + This can lead to impurities (such as residual copper ammonium complexes) or crystallization defects. The concentration of ammonium chloride needs to be strictly controlled between 22 and 88 mmol / L to balance dissolution promotion and purity assurance; 66 mmol / L is the optimal solution for industrial applications.

[0093] Examples 6-7 and Comparative Examples 10-12

[0094] Examples 6-7 and Comparative Examples 10-12 respectively provide a method for preparing high-purity copper glycine from electronic waste using an amino acid composite reagent system. The difference from Example 1 is that the concentration of hydrogen peroxide solution is different, as shown in Table 4. The rest is roughly the same as Example 1 and will not be repeated here.

[0095] Table 4. Hydrogen peroxide solution concentration, copper leaching effect, and product indicators in Examples 1, 6-7 and Comparative Examples 10-12.

[0096]

[0097] Table 4 shows that the concentration of hydrogen peroxide (H2O2) needs to be strictly controlled to balance oxidative leaching and glycine protection. Without H2O2 (Comparative Example 10), the copper leaching rate (55.9%) and yield (12.0%) are extremely low, demonstrating its crucial role in oxidative dissolution of copper. The optimal range is 10–90 ml / L, where the leaching rate (95.2–96.2%), yield (71.3–89.5%), and purity (99.0–99.2%) are all optimal. When the hydrogen peroxide solution concentration is ≥100 ml / L (Comparative Example 12), although the leaching rate is acceptable, the purity drops sharply to 93.5%, mainly because excessive H2O2 oxidizes the α-amino group of glycine to generate aldehyde byproducts (such as glyoxylic acid), destroying the chelate structure and introducing impurities. In summary, an H2O2 concentration of 50 ml / L is the optimal industrial concentration, achieving both efficient leaching and ensuring product purity.

[0098] Examples 8-9 and Comparative Examples 13-15

[0099] Examples 8-9 and Comparative Examples 13-15 respectively provide a method for preparing high-purity copper glycine from electronic waste using an amino acid composite agent system. The difference between these methods and Example 1 is that the stirring time in step (2) is different, while the rest is roughly the same as in Example 1, and will not be repeated here.

[0100] Comparative Examples 16-20

[0101] Comparative Examples 16-20 provide a method for preparing high-purity copper glycine from electronic waste using an amino acid composite reagent system. The difference between these methods and Examples 8-9 and Comparative Examples 13-15 is that ammonium chloride is not introduced. The rest is roughly the same as in Example 1 and will not be repeated here.

[0102] Table 5. The molar concentration of ammonium chloride, copper leaching effect, and product indicators in Examples 1, 8-9 and Comparative Examples 10, 13-20.

[0103]

[0104] Table 5 shows that the synergistic effect of ammonium chloride and leaching time has a decisive influence on copper leaching efficiency and product quality. The core value of ammonium chloride is that, at the same leaching time (e.g., 36 hours), the leaching rate (69.9%) and purity (65.8%) of the group without ammonium chloride (Comparative Example 7) were significantly lower than those of the group containing ammonium chloride (Example 1: 95.7%, 99.2%), proving that NH4... + The formation of a copper-ammonia complex accelerates copper dissolution and ensures a high degree of chelation. Examples 1, 8-9: Leaching rate / yield increased over time (24h→48h: 93.1%→98.2%). After 48h (Comparative Example 15), the purity dropped to 97.3%, indicating the accumulation of side reactions that led to a decrease in product purity.

[0105] The comparative group without ammonium chloride: even with an extension of 52 h (Comparative Group 20), the leaching rate (84.9%) and purity (68.2%) were still severely limited, revealing the lack of NH4. + Under these conditions, time compensation is ineffective.

[0106] Comparative Example 21

[0107] Comparative Example 21 provides a method for preparing high-purity copper glycine from electronic waste using an amino acid composite agent system. The difference from Example 1 is that no current or magnetic field is introduced in step (4). The rest is roughly the same as Example 1 and will not be repeated here.

[0108] Table 6 Product indicators in Example 1 and Comparative Example 21

[0109]

[0110] The comparison of data in Table 6 leads to the following clear conclusions: Direct evaporation and crystallization without introducing current or a magnetic field significantly reduced the yield, purity, and crystal quality of copper glycinate. Specifically, the yield decreased from 87.5% to 71.9%, the purity from 99.2% to 90.6%, and the crystal state changed from "perfect" to "imperfect." This clearly demonstrates that introducing current and a magnetic field plays a crucial role in optimizing the process; it effectively improves product yield, ensures high purity, and promotes the formation of a complete crystal structure.

[0111] Comparative Example 22

[0112] Comparative Example 22 provides a method for preparing high-purity copper glycine from electronic waste using an amino acid composite agent system. The difference from Example 1 is that gradient evaporation was not used in step (4), but isothermal evaporation at 50°C for 24 hours was used directly. The rest is roughly the same as Example 1, and will not be repeated here.

[0113] Table 7 Product Indicators in Example 1 and Comparative Example 22

[0114]

[0115] As shown in Table 7, compared with Example 1 which used gradient evaporation, the yield of the copper glycine product obtained by isothermal evaporation at 50°C in Comparative Example 22 was the same, but the purity was significantly reduced to only 21.4%, and the crystal integrity was poor, with a large number of impurities in the product. This indicates that the gradient evaporation process is crucial for obtaining high-purity, crystal-complete copper glycine products, while single high-temperature isothermal evaporation is not conducive to the effective separation of impurities and high-quality crystal growth.

[0116] This application also investigated why the amino acid composite agent system could not achieve 100% leaching of copper from electronic waste (waste printed circuit board) powder samples. Cross-sectional backscattered SEM images of the waste printed circuit board powder samples, SEM images after leaching, magnified SEM images after leaching, and energy dispersive spectroscopy (EDS) analysis images were captured, as shown below. Figure 2 As shown in (a), (b) and (c).

[0117] Depend on Figure 2 It can be inferred that the powder sample has a layered structure, which causes some copper to be trapped in the epoxy resin layer, preventing it from contacting the reagent and resulting in mass transfer resistance.

[0118] In summary, this application provides an amino acid composite reagent system and a method for preparing high-purity copper glycine from electronic waste. By designing the amino acid composite reagent system and constructing an ammonia catalytic barrier reduction mechanism, the oxidation energy barrier for the conversion of copper(O) to copper(II) is lowered, increasing the leaching rate by more than 50%. Simultaneously, the dual effects of copper hydroxide precipitation and glycine chelation are inhibited, achieving efficient copper ion storage. During the electronic waste leaching process, a narrow-window pH control technology at 9.5±0.2 is used to simultaneously maintain ammonia stability and glycine anion activity within this critical range, ensuring selective copper leaching. Furthermore, the self-purification properties of the leachate are utilized to induce in-situ crystallization of the glycine-copper complex, directly preparing chemical-grade copper glycine products. A directional crystallization process for leachate was constructed, utilizing the "self-assembly directional crystallization" process of glycine copper chelate. Based on the saturated concentration and stable chelate structure of glycine copper in the leachate, high-purity crystals were prepared in one step through precise control of three-stage crystallization: Under the critical window of pH 9.5±0.2 and low-temperature evaporation conditions of 30℃, the self-assembly growth of [Cu(Gly)2] molecules along the (001) crystal plane was triggered, forming needle-like crystals with an aspect ratio >10 (SEM verification showed a size of 5~30μm). Simultaneously, magnetic field-assisted crystallization induced the directional alignment of [Cu(Gly)2] molecules along the crystal plane, inhibiting impurity eutectic; at the same time, the ammonia synergistic regulation mechanism was used to deeply inhibit impurity eutectic (Fe 2+ / Pb 2+The residual concentration is <50ppm), and the crystal purity is >98.0%, meeting industrial-grade standards. This technology eliminates three energy-intensive purification processes: extraction, back-extraction, and electrolysis. The mother liquor is recycled through amino acid regeneration, achieving a closed-loop crystallization system with "zero seed crystal addition and zero wastewater discharge" for complex copper-containing leaching solutions from electronic waste.

[0119] 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 preparing high purity glycine copper from electronic waste using an amino acid complexing agent system, characterized by, The method comprises the following steps: S1. crushing electronic waste to obtain a crushed sample; S2. adding water to the crushed sample and stirring to obtain a slurry; S3. adding an amino acid complexing agent system to the slurry, adjusting the pH value, stirring and leaching, and then performing solid-liquid separation to obtain a leaching solution; S4. performing targeted impurity removal pretreatment on the leaching solution to obtain a pretreated leaching solution; S5. The pre-treated leachate was placed in the center of the Helmholtz coil, the current was turned on and the magnetic field strength at the center was calibrated, the first evaporation was carried out, and the Raman spectrum of the crystal in the evaporation was monitored in real time 518 cm -1 The intensity of the peak was monitored until the crystal nucleus induction was completed, then the second evaporation was carried out, followed by the third evaporation, to obtain a high-crystallinity glycine copper crystal; The amino acid complexing agent system comprises an amino acid chelating agent, an amine auxiliary agent, and a hydrogen peroxide solution; the amino acid chelating agent comprises glycine or a dipeptide and a polypeptide containing a glycine structural fragment, and the amine auxiliary agent comprises at least one of ammonia, ammonium chloride, and propylenediamine; The mass concentration of the amino acid chelating agent is 20-40 g / L, the molar concentration of the amine auxiliary agent is 22-88 mmol / L, and the concentration of the hydrogen peroxide solution is 10-90 ml / L; In the pH value adjustment, the pH value adjusting agent is sodium hydroxide, and the pH value is 9.3-9.7; The temperature of the first evaporation is 49.8~50.2℃, and the intensity of the Raman spectrum 518cm -1 The intensity of the peak is refractive index of 1.385; the temperature of the second evaporation is 39.8~40.2℃, and the evaporation time is 120min; the third evaporation is performed by cooling at a rate of 0.2℃ / min to 24.8~25.2℃, and then evaporating for 24h; In the third evaporation, the relative humidity of evaporation is 30%; The electric current is 6.25 A, and the central point magnetic field strength is 0.50±0.01 T; The targeted impurity removal pretreatment comprises the following steps: To the leach liquor was added NH4 + - ZSM-5 zeolite, 30 min at room temperature with magnetic stirring at 300 rpm, then filtered.

2. The method of claim 1, wherein the high purity glycine copper is prepared by treating the electronic waste with the amino acid complexing agent system, and In step S3, the stirring and leaching time is 24-48 h.

3. The method of claim 1, wherein the high purity glycine copper is prepared by treating the electronic waste with the amino acid complexing agent system, and In step S1, the particle size of the crushed sample is less than 50 mesh.

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