Method for enriching elemental gold from electronic waste

Abstract

The application provides a method for enriching elemental gold from electronic waste, and belongs to the technical field of precious metal recycling. The method utilizes the dual function of glycine in material preparation and application to achieve efficient and selective capture of elemental gold particles in the form of plating layer on the surface of nickel matrix by manganese dioxide. Specifically, the amino group of glycine is complexed with the oxidation product Mn 4+ , and Mn 4+ does not exist in ionic form in an alkaline environment, and finally generates manganese dioxide. The coordination effect of glycine effectively regulates the nucleation and growth kinetics of manganese dioxide, inhibits the generation of dense precipitates, and guides the self-assembly of manganese dioxide into a three-dimensional interconnected sponge-like structure with coexistence of large pores-mesopores-micropores. The structure provides a large specific surface area and rich mass transfer channels for the subsequent capture behavior. The application solves the problem of direct enrichment of solid elemental gold.

Description

Technical Field

[0001] This invention relates to the field of gold-containing solid waste resource utilization, and more particularly to a method for enriching elemental gold from electronic waste. Background Technology

[0002] With the rapid development of the electronics and information industry, the amount of electronic waste generated has surged year by year. The precious metals such as gold and silver contained in this waste have earned it the reputation of being an "urban mine." In particular, gold-plated components on various electrical connectors, contacts, and printed circuit boards (PCBs) are important sources of gold resources for recycling. These components are typically made of elemental gold, electroplated or chemically plated onto a nickel underlayer, forming a typical "Au-Ni" composite structure. However, how to efficiently, economically, and environmentally recover gold from such complex structures has always been a technological challenge in this field.

[0003] Researchers have explored physical beneficiation methods, such as electrostatic separation, gravity separation, or flotation, to enrich gold-bearing materials after crushing. However, for gold tightly bound in the "Au-Ni" composite structure, physical methods are extremely inefficient because gold and nickel have similar physical properties such as density and conductivity, and the gold coating is usually too thin to be effectively dissociated and separated through physical crushing.

[0004] In recent years, adsorption methods have received widespread attention due to their simplicity and environmental friendliness. However, existing adsorbents (such as activated carbon, ion exchange resins, and functionalized silica gels) are generally designed for gold ions in solution. They are completely ineffective against solid elemental gold particles or plating because their mechanism of action relies on coordination or electrostatic attraction with gold ions. Therefore, without a leaching step, these adsorbents cannot be directly used for the recovery of gold-plated materials.

[0005] Developing a novel adsorbent material and technology that can selectively capture and enrich elemental gold directly from solid mixtures without a dissolution step has become a technological gap that urgently needs to be filled in this field.

[0006] In addition, although manganese dioxide is a common metal oxide in the field of materials synthesis, manganese dioxide prepared by traditional methods often suffers from problems such as small specific surface area, unsatisfactory pore structure and uncontrollable morphology, which limits its application as a highly efficient adsorbent.

[0007] Therefore, there is an urgent need for a method that can simultaneously achieve precise control of the microstructure of manganese dioxide materials and enable them to directly capture solid elemental gold. Summary of the Invention

[0008] To address the current problem of not being able to directly capture elemental gold when recovering gold from gold-plated components in electronic waste, this application provides a green, efficient, and directly enrichable adsorption material and method for elemental gold.

[0009] This application presents a sponge-like manganese dioxide adsorbent material and its application method for enriching elemental gold from electronic waste. The core of this technology lies in utilizing specific small-molecule amino acids as "molecular bridges" and "structure directing agents" to achieve efficient and selective capture of elemental gold particles existing in the form of a nickel substrate by manganese dioxide.

[0010] The term "molecular bridge" specifically refers to a bifunctional organic small molecule that can establish a directional and stable connection between a solid adsorbent and the target precipitate during adsorption. Its core mechanism lies in the presence of different and specific chemical functional groups at both ends of the molecule, which can simultaneously interact strongly with the solid surfaces on both sides through a defined chemical bonding mechanism. Specifically, one functional group preferentially binds to nickel atoms on the gold-plated nickel surface through coordination bonds to form a surface complex, while the other functional group preferentially binds to active sites on the spongy manganese dioxide surface through coordination bonds or hydrogen bonds. Therefore, this "molecular bridge" is a defined chemical entity that achieves a specific and strong connection between two macroscopic solid particles through the aforementioned "dual-anchoring" chemical bonding mechanism. Its function is to transform weak, non-selective physical adsorption into strong, specific chemical bonding.

[0011] The "structure-directing agent" refers to a chemical reagent that can regulate the formation of a hierarchical porous structure in the synthesis of sponge-like manganese dioxide. Its mechanism of action includes: firstly, acting as a ligand, it complexes with the manganese precursor through functional groups, regulating the reaction pathway; subsequently, it or its derivatives intercalate between manganese dioxide particles, preventing dense packing; and finally, it guides the manganese dioxide to self-assemble around a fixed molecular model, forming a three-dimensional sponge with a macroporous-mesoporous-microporous hierarchical structure. This achieves cross-scale regulation from molecular coordination to macroscopic structure, making it a key component in the preparation of high-performance adsorbent materials.

[0012] The mechanism of action of this application spans the entire process from material synthesis to target capture. It is not based on the dissolution of gold, but relies on precise molecular recognition and chemical bonding that occurs at the solid-liquid-solid multiphase interface.

[0013] First, based on the deterministic chemical bonding mechanism of "carboxyl-nickel coordination" and "amino-manganese bonding," and the synthetic mechanism of glycine-induced sponge-like structure formation, this application reveals the dual function of glycine in material preparation and application.

[0014] In the material synthesis stage, glycine acts as a reducing agent and undergoes a redox reaction with potassium permanganate. The key mechanism lies in the fact that the amino group of glycine can react with the oxidation product Mn. 4+ Isocomplexation, Mn 4+In an alkaline environment, manganese dioxide does not exist in ionic form and eventually forms. The coordination effect of glycine effectively regulates the nucleation and growth kinetics of manganese dioxide, inhibiting the formation of dense precipitates and guiding the self-assembly of manganese dioxide into a three-dimensional interconnected sponge-like structure with macropores, mesopores, and micropores. This unique structure provides a huge specific surface area and abundant mass transfer channels for subsequent capture behavior.

[0015] During application, when this sponge-like manganese dioxide comes into contact with gold-plated nickel particles in the presence of glycine, a precise chemical bond occurs: the glycine molecule, with its carboxyl group (-COO), forms a bond. - The two oxygen atoms on the nickel plating (Ni) act as bidentate ligands, coordinating with the empty d orbitals of the exposed nickel atoms (Ni) on the gold-plated nickel surface to form a stable surface complex. This complex is insoluble in the aqueous phase, thus forming only a molecular film on the surface of the nickel-gold material that subsequently interacts with the spongy manganese dioxide. Simultaneously, the nitrogen atom in the amino group (-NH2) at the other end, with its lone pair electrons, interacts with the unsaturated manganese sites (Mn) on the surface of the spongy manganese dioxide framework. 4+ Coordination bonding or hydrogen bonding of the hydroxyl groups in MnO(OH)2 occurs. This series of determined chemical reactions successfully constructed a directional "molecular bridge" based on chemical bonds between the gold / nickel surface and the manganese dioxide adsorbent.

[0016] Second, the interfacial interaction has shifted from weak physical adsorption to strong chemical bonding.

[0017] This application achieves a fundamental change in the target analyte capture mechanism through the aforementioned determined chemical bonding mechanism. Ordinary physisorption relies on weak and non-selective van der Waals forces. However, in this application, the coordination bonds between the glycine carboxyl group and nickel, and the coordination / hydrogen bonds between the glycine amino group and manganese dioxide surface sites, have bond energies far exceeding those of physical forces. This "double-anchoring" structure, composed of two strong chemical bonds, is equivalent to establishing a robust "chemical chain" between the gold-plated nickel particles and manganese dioxide. Its binding strength and specificity represent a mechanistic leap from reversible, random physisorption to irreversible, directional chemical bonding.

[0018] Third, this application does not treat material synthesis and application as isolated steps, but rather as a coherent system. The synthesis of the spongy manganese dioxide relies on small bifunctional molecules such as glycine as a reaction medium and structure directing agent to obtain its unique three-dimensional interconnected hierarchical porous structure. It is precisely this spongy structure that provides the physical basis for gold capture in applications: its high specific surface area and the massive number of surface active sites ensure that there are enough amino anchoring sites to support glycine molecular bridges. This unity of mechanism from synthesis to application allows the "molecular bridging-chemical anchoring" mechanism to occur efficiently and on a large scale throughout the entire adsorbent, thereby achieving efficient conversion of elemental gold particles from a dispersed state to an enriched state.

[0019] In summary, this invention solves the problem of direct enrichment of solid elemental gold by clearly defining the glycine-induced sponge-like structure formation mechanism and the double bonding application mechanism of "carboxyl-nickel coordination" and "amino-manganese bonding", providing a brand-new solution for the efficient recycling of precious metals from electronic waste.

[0020] This application provides a method for enriching elemental gold from electronic waste, comprising the following steps:

[0021] S1, Grind the electronic waste to obtain a slurry, and adjust the pH of the slurry to a predetermined pH;

[0022] S2, add glycine and potassium permanganate to the reaction vessel containing the slurry, and stir continuously at room temperature for a specified time; after the reaction is completed, while stirring, continuously introduce deionized water at a constant flow rate through the water inlet set at the bottom of the reaction vessel; collect the suspension overflowing from the reaction vessel, separate the solid and liquid, collect the filter cake, and obtain a spongy manganese dioxide material enriched with elemental gold.

[0023] The gold content in spongy manganese dioxide materials enriched with elemental gold was determined by fire assay, and the test and analysis methods were in accordance with GB / T 7739.

[0024] The gold recovery rate is used to determine the extent of gold recovery.

[0025]

[0026] In the formula, η represents the gold recovery rate, in %; m1 represents the mass of the raw material, in g; β1 represents the grade of the raw material, in g / t; m2 represents the mass of the solid after solid-liquid separation, in g; and β2 represents the grade of the solid after solid-liquid separation, in g / t.

[0027] Furthermore, the predetermined pH is 12-14.

[0028] Further, in step S2, the concentration of glycine is 0.5~2 mol / L.

[0029] Further, in step S2, the concentration of potassium permanganate is 0.05~0.2 mol / L.

[0030] Furthermore, in step S2, the stirring reaction is specified for a time of 30 to 60 minutes.

[0031] Furthermore, the electronic waste includes at least one of waste circuit boards, integrated chips, and waste electrode materials.

[0032] Furthermore, during the grinding process, the electronic waste is ground until the content of particles smaller than 100 mesh accounts for 95%-98% of the total mass of the mineral powder.

[0033] Furthermore, the mass concentration of the slurry is 10%-30%.

[0034] Furthermore, the method for adjusting the pH value of the slurry is to add a pH adjuster; the pH adjuster is sodium hydroxide.

[0035] The beneficial effects of this application are as follows:

[0036] Compared with existing precious metal recycling technologies, this application achieves a comprehensive improvement in material properties, process flow and overall benefits, with significant and multi-dimensional gains.

[0037] 1. A qualitative leap has been achieved in material properties and adsorption mechanisms, moving from "extensive capture" to "precise capture." Traditional adsorbents rely on limited physical adsorption or coordination with gold ions. However, the sponge-like manganese dioxide material prepared in this application, through the "structure-directing" effect of glycine, is endowed with a unique three-dimensional hierarchical porous structure. Its huge specific surface area and high density of surface active sites provide a solid physical basis for efficient adsorption. More importantly, the dual anchoring mechanism of "carboxyl-nickel coordination" and "amino-manganese bonding" established by glycine as a "molecular bridge" elevates the adsorption effect from the weak, reversible van der Waals force level to the strong, specific, and irreversible chemical bonding level. This mechanism allows the adsorbent to act like a "smart magnet," precisely identifying and firmly capturing elemental gold particles in the form of plating in complex electronic waste fragments, while ignoring the large number of other coexisting base metal impurities. This not only increases the adsorption capacity of elemental gold to several times that of traditional physical adsorption methods, but also achieves unprecedented high selectivity, fundamentally solving the problem of selective recovery of gold in complex systems and laying the foundation for obtaining high-purity enriched products.

[0038] 2. The process has been simplified from "complex and high-risk" to "simple and green" in terms of process flow and operating costs. Existing technologies for recovering gold from gold-plated parts must involve leaching with strong acids or highly toxic cyanides to convert solid gold into ionic form. This process has drawbacks such as corroding equipment, high reagent consumption, and high costs for subsequent wastewater treatment.

[0039] This application completely bypasses the gold dissolution step, achieving gold transfer and enrichment directly under solid-phase conditions through molecular bridging. The process only requires mixing and stirring the material and adsorbent in a conventional reactor under mild room temperature conditions; it is simple, safe, and requires minimal equipment.

[0040] Meanwhile, the glycine and potassium permanganate used in this application are both inexpensive and low-toxic industrial raw materials, eliminating the use of cyanide at the source. The entire process is clean and environmentally friendly, with extremely low waste treatment load, significantly reducing environmental compliance costs and safety risks. This "leaching-free" process design simplifies the traditional multi-step, lengthy process of "crushing-leaching-separation-adsorption-reduction" into an extremely short path of "mixing-adsorption-separation," significantly shortening the process cycle, improving processing efficiency, and bringing considerable operating cost savings due to the reduction in reagents and energy consumption.

[0041] 3. It demonstrates outstanding comprehensive value and broad application prospects in terms of final recycling benefits and technological extensibility. Based on the aforementioned material and process advantages, this technology can ultimately concentrate elemental gold in electronic waste into the adsorption phase with high recovery rate and high enrichment ratio, greatly simplifying the subsequent refining and purification steps and reducing costs, thereby improving the economics of the entire recycling chain.

[0042] The adsorbed material can be recycled for gold and regenerated for adsorbent through simple acid washing or heat treatment, which embodies the concept of circular economy.

[0043] Furthermore, this technology is highly versatile and applicable not only to various types of gold-plated electronic waste, but its "molecular bridging" and "multi-level channel trapping" concepts can also provide a new technological paradigm for recovering valuable components from other complex solid wastes containing precious metals (such as spent catalysts and alloy waste).

[0044] Therefore, this invention not only provides a solution to the key bottlenecks in the development of "urban mines", but also, with its significant advantages of being green, efficient and low-cost, injects strong impetus into the technological upgrading of the resource recycling industry, and has extremely high commercial value and broad social benefits. Attached Figure Description

[0045] 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.

[0046] Figure 1 Photos of electronic waste before and after disassembly.

[0047] Figure 2 Backscattered image of an iron-nickel-gold sample from electronic waste.

[0048] Figure 3 This is a surface distribution diagram of iron, nickel, and gold elements in electronic waste.

[0049] Figure 4 The images shown are actual pictures of the suspended matter generated in Example 1. The left image is a picture of the material collected after filtration, and the right image is a picture of the material after drying and grinding.

[0050] Figure 5 This is an elemental energy dispersive spectroscopy (EDS) analysis diagram of electronic waste.

[0051] Figure 6 This is a scanning electron microscope image of the suspended material encapsulated in Example 1 when the potassium permanganate concentration was 0.075 mol / L.

[0052] Figure 7 The images and XRD patterns of the suspended matter generated in Example 1 are shown. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0055] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0056] This application provides a method for enriching elemental gold from electronic waste, comprising the following steps:

[0057] S1, Grind the electronic waste to obtain a slurry, and adjust the pH of the slurry to a predetermined pH;

[0058] Electronic waste includes at least one of waste circuit boards, integrated chips, and waste electrode materials.

[0059] Specifically, during the grinding process, electronic waste is ground until the content of particles smaller than 100 mesh accounts for 95%-98% of the total mass of the mineral powder; then, water is added to the electronic waste powder and stirred to obtain a slurry with a mass concentration of 10%-30%, and sodium hydroxide is added to adjust the pH of the slurry to 12-14.

[0060] S2, add glycine and potassium permanganate to the reaction vessel containing the slurry, and stir continuously at room temperature for 30-60 minutes; after the reaction is completed, while stirring, continuously introduce deionized water at a constant flow rate through the water inlet set at the bottom of the reaction vessel; collect the suspension overflowing from the reaction vessel, separate the solid and liquid, collect the filter cake, and obtain spongy manganese dioxide material enriched with elemental gold.

[0061] The gold content in spongy manganese dioxide materials enriched with elemental gold was determined by fire assay, and the test and analysis methods were in accordance with GB / T 7739.

[0062] The gold recovery rate is used to determine the extent of gold recovery.

[0063]

[0064] In the formula, η represents the gold recovery rate, in %; m1 represents the mass of the raw material, in g; β1 represents the grade of the raw material, in g / t; m2 represents the mass of the solid after solid-liquid separation, in g; and β2 represents the grade of the solid after solid-liquid separation, in g / t.

[0065] The concentration of glycine is 0.5~2 mol / L.

[0066] The concentration of potassium permanganate is 0.05~0.2 mol / L.

[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] Please see Figures 1 to 5As shown, this embodiment provides a method for enriching elemental gold from electronic waste, including the following steps:

[0070] S1. Grind the printed circuit board powder to a particle size of less than 100 mesh to obtain small particulate material with a gold grade of 1.709 g / t. Add 1 L of water to 200 g of printed circuit board powder and stir. The slurry concentration is 20%. Add sodium hydroxide to adjust the pH of the slurry to 13.

[0071] S2. Glycine and potassium permanganate were added to a reaction vessel containing mineral slurry; wherein, 75.05 g of glycine (mass concentration 1 mol / L) and 11.85 g of potassium permanganate (mass concentration 0.075 mol / L) were added. The reaction was then stirred continuously at room temperature for 40 min. After the reaction, while maintaining stirring, deionized water was continuously introduced at a constant flow rate of 10 L / h through an inlet located at the bottom of the reaction vessel, for a total flow rate of 5 L. The overflow suspension in the reaction vessel was then collected, and solid-liquid separation was performed using a vacuum filtration device. The filter cake was finally collected, yielding a sponge-like manganese dioxide material (solid) enriched with elemental gold. Figure 4 As shown.

[0072] Comparative Example 1

[0073] S1. Grind the printed circuit board powder to a particle size of less than 100 mesh to obtain small particulate material with a gold grade of 1.709 g / t. Add 1 L of water to 200 g of printed circuit board powder and stir. The slurry concentration is 20%. Add sodium hydroxide to adjust the pH of the slurry to 13.

[0074] S2. Add 6.53 g of manganese dioxide (0.075 mol / L) to a reaction vessel containing mineral slurry. Then, stir the mixture continuously for 40 min at room temperature. After the reaction is complete, while maintaining stirring, continuously introduce deionized water at a constant flow rate of 10 L / h through the inlet located at the bottom of the reaction vessel, for a total flow rate of 5 L. Then, collect the suspension overflowing from the reaction vessel and perform solid-liquid separation.

[0075] The gold content in the solids of Example 1 and Comparative Example 1 was determined by fire assay, and the analytical method was in accordance with GB / T 7739. The test results are shown in Table 1.

[0076] The gold recovery rate is used to determine the extent of gold recovery.

[0077]

[0078] In the formula, η represents the gold recovery rate, in %; m1 represents the mass of the raw material, in g; β1 represents the grade of the raw material, in g / t; m2 represents the mass of the solid after solid-liquid separation, in g; and β2 represents the grade of the solid after solid-liquid separation, in g / t.

[0079] Table 1 Test results of Example 1 and Comparative Example 1

[0080]

[0081] As shown in Table 1, a manganese dioxide material with a unique sponge-like flocculent morphology was generated in situ under alkaline conditions through the synergistic effect of glycine and potassium permanganate. This material exhibited excellent adsorption performance for gold, achieving a gold recovery rate of 42%, and the gold content in the adsorbed material reached 31.2 g / t.

[0082] This result fully verifies the effectiveness of the "molecular bridge-structure guidance" dual mechanism constructed in this invention: glycine not only guides the formation of sponge-like manganese dioxide with a large specific surface area and rich pore structure, but its molecules also act as a chemical bridge connecting gold particles and manganese dioxide in the subsequent adsorption process, thereby achieving efficient capture of elemental gold.

[0083] Scanning electron microscopy backscattered image of spongy manganese dioxide, as shown below Figure 6 As shown. The morphology of sponge-like manganese dioxide can be systematically observed through observation windows of different gradients (100µm~5µm). The manganese dioxide generated in situ in Example 1 exhibits a sponge-like morphology. When the observation window is magnified, as shown... Figure 6 As shown in (c), the gold-containing material can be seen adsorbed within the three-dimensional pores.

[0084] To further determine the composition of the flocculent suspension generated in Example 1, it was collected, washed, ground, and dried, and then subjected to XRD characterization tests. The results are as follows: Figure 7 As shown.

[0085] Analysis of the XRD pattern reveals that the measured diffraction peaks belong to the diffraction card MnO2 (PDF#89-5171) in the ICDD powder diffraction database. Specifically, the diffraction peaks at 36.8°, 42.5°, 56.9°, and 67.1° are attributed to the (100), (101), (102), and (110) crystal planes of MnO2, respectively. The pattern shows no impurity peaks, and the peak shapes are sharp, perfectly matching the characteristic peaks of the standard MnO2 card, confirming that the main component of the suspended matter is manganese dioxide.

[0086] Comparative Example 1 used a method of directly adding ordinary manganese dioxide powder.

[0087] The results showed that the gold recovery rate was 0, and the gold grade in the adsorbed material was also 0. This significant difference demonstrates that ordinary manganese dioxide powder, without special structural design and surface functionalization, despite having the same chemical composition, is completely incapable of effectively enriching elemental gold due to the lack of a specific three-dimensional hierarchical porous structure and surface active sites.

[0088] Examples 2-3 and Comparative Examples 2-3

[0089] The difference from Example 1 is that the pH of the slurry is different in step S1. Otherwise, it is roughly the same as Example 1 and will not be repeated here.

[0090] Table 2 Test results of Examples 1-3 and Comparative Examples 2-3

[0091]

[0092] Table 2 shows that the pH value of the slurry has a decisive influence on the gold recovery effect and the morphology of manganese dioxide. Under alkaline conditions (pH=12-14), Examples 1-3 successfully generated sponge-like manganese dioxide with three-dimensional hierarchical channels, and the gold recovery rate increased positively with increasing pH (from 42% to 51%); while when pH<12, Comparative Examples 2-3 only generated dense powdery manganese dioxide, and the gold recovery rate was zero.

[0093] This phenomenon can be explained by potentiometrics and interfacial reaction mechanisms: a higher pH environment protects the glycine carboxyl group (-COO-). - The full ionization of manganese dioxide enhances its coordination ability with nickel atoms. By regulating the redox potential of the system, the reduction process of potassium permanganate tends to generate a sponge-like structure with highly active surface sites. At the same time, the degree of hydroxylation on the surface of manganese dioxide increases under alkaline conditions, making it easier to form stable hydrogen bonds / coordinate bonds with glycine amino groups, thereby constructing an efficient "molecular bridge" dual anchoring system. Conversely, low pH conditions inhibit the ionization of functional groups and interfacial bonding, causing manganese dioxide to precipitate rapidly into amorphous powder and lose its selective adsorption capacity.

[0094] Examples 4-5 and Comparative Examples 4-5

[0095] The difference from Example 1 is that the glycine concentration is different in step S2, but the rest is roughly the same as in Example 1, and will not be repeated here.

[0096] Table 3 Test results of Examples 1, 4-5 and Comparative Example 4-5

[0097]

[0098] As shown in Table 3, the molar concentration of glycine has a significant impact on the gold recovery rate.

[0099] Within a suitable concentration range (0.5-2 mol / L), Examples 1, 4, and 5 all generated sponge-like flocculent manganese dioxide, with gold recovery rates maintained above 40%, and the gold grade after adsorption reaching 29.8-39.2 g / t. However, when the concentration was too low (0.4 mol / L) or too high (2.5 mol / L), although Comparative Examples 4-5 still generated a sponge-like structure, the gold recovery rates were significantly reduced (30% and 29%, respectively).

[0100] This phenomenon can be explained by the "molecular bridging" effect and reaction kinetics of glycine: at appropriate concentrations, glycine can act as a reducing agent to undergo a controlled redox reaction with potassium permanganate, guiding manganese dioxide to nucleate and self-assemble into a hierarchical porous sponge structure through coordination effects. It can also provide sufficient amino and carboxyl functional groups to construct "dual-anchoring" chemical bonds at the solid-liquid-solid interface (carboxyl groups coordinate with nickel, and amino groups bond with the surface of manganese dioxide), thereby efficiently capturing elemental gold. Conversely, when the concentration is too low, glycine is insufficient to maintain sufficient structural guidance and bonding sites, while when the concentration is too high, the reaction is too fast, generating mixed solid powder, which destroys the uniformity of the pores and results in uneven distribution of surface active sites, thereby reducing the gold adsorption efficiency.

[0101] Examples 6-8 and Comparative Examples 6-7

[0102] The difference from Example 1 is that the molar concentration of potassium permanganate is different in step S2. Otherwise, it is roughly the same as Example 1 and will not be repeated here.

[0103] Table 4. Test results of Examples 1, 6-8 and Comparative Examples 6-7

[0104]

[0105] As shown in Table 4, the molar concentration of potassium permanganate has a significant impact on the gold recovery rate.

[0106] Within a suitable concentration range (0.05-0.20 mol / L), Examples 1, 6, 7, and 8 all produced sponge-like flocculent manganese dioxide, with gold recovery rates maintained between 38% and 47%, and the gold grade after adsorption reaching 30.0-33.4 g / t. However, when the concentration was too low (0.02 mol / L), Comparative Example 6 could not produce collectable manganese dioxide products, and the recovery rate was zero. When the concentration was too high (0.25 mol / L), although Comparative Example 7 produced a sponge-like structure, the gold recovery rate dropped sharply to 5%.

[0107] This phenomenon can be explained through reaction kinetics and interfacial chemistry: at appropriate concentrations, potassium permanganate undergoes a controlled redox reaction with glycine, guiding manganese dioxide to nucleate and self-assemble into a hierarchical porous sponge-like structure through coordination effects, thus providing sufficient surface active sites for gold adsorption. Conversely, if the concentration is too low, the reaction is incomplete, and an effective adsorbent cannot be formed; if the concentration is too high, the reaction is too fast, resulting in a reduced mass of manganese dioxide and potential structural damage, leading to a decrease in adsorption capacity. Simultaneously, excessively high potassium permanganate concentrations oxidize gold into ionic form, and the gold ions combine with glycine anions, entering the solution phase.

[0108] Examples 9-11 and Comparative Examples 8-10

[0109] The difference from Example 1 is that the reaction time is different in step S2, but the rest is roughly the same as in Example 1, and will not be repeated here.

[0110] Table 5 Test results of Examples 1, 9-11 and Comparative Examples 8-10

[0111]

[0112] As shown in Table 5, the reaction time has a significant impact on the gold recovery rate.

[0113] Within a suitable reaction time (30-60 minutes), Examples 1, 9, and 10 all produced spongy flocculent manganese dioxide, with gold recovery rates maintained between 35% and 53%, and the gold grade after adsorption reaching 29.8-35.2 g / t. However, when the reaction time was too short (10-20 minutes), Comparative Examples 8 and 9 had extremely low gold recovery rates (only 4% for Comparative Example 9) due to insufficient reaction, resulting in low manganese dioxide production or incomplete structure. When the reaction time was too long (60-65 minutes), the gold recovery rates of Examples 11 and 10 decreased significantly (21% and 12%, respectively). This was because the potassium permanganate and glycine system began to dissolve the gold, causing it to enter the liquid phase instead of being adsorbed onto the manganese dioxide.

[0114] This phenomenon can be explained by reaction kinetics and redox potential chemistry: at a moderate reaction time, the redox reaction between glycine and potassium permanganate reaches equilibrium, guiding manganese dioxide to self-assemble into a hierarchical porous sponge structure and providing stable "molecular bridge" bonds (carboxyl groups coordinate with nickel, and amino groups bond with the surface of manganese dioxide), thereby efficiently capturing elemental gold; conversely, if the time is too short, the reaction is incomplete and there are insufficient adsorption sites; if the time is too long, the oxidative properties of the system increase, and gold is oxidized into soluble complexes that enter the solution. At the same time, the manganese dioxide structure may overgrow or precipitate, reducing the adsorption capacity.

[0115] 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 of enriching elemental gold from electronic waste, characterized by, The method comprises the following steps: S1, grinding the electronic waste to obtain a slurry, and adjusting the pH value of the slurry to 12-14; S2, adding glycine and potassium permanganate into a reaction container containing the slurry, continuously stirring at room temperature for a specified time, so that the glycine and the potassium permanganate react in the alkaline slurry to generate three-dimensional interconnected sponge-like manganese dioxide in situ, and the glycine acts as a molecular bridge, the carboxyl group of the glycine coordinates with the nickel atoms under the gold-plated layer in the electronic waste, and the amino group of the glycine bonds with active sites on the surface of the sponge-like manganese dioxide, thereby capturing and enriching the elemental gold particles on the sponge-like manganese dioxide; after the reaction is completed, deionized water is continuously introduced at a constant flow rate through a water inlet arranged at the bottom of the reaction container under stirring; the overflowed suspension in the reaction container is collected, solid-liquid separation is performed, the filter cake is collected, and sponge-like manganese dioxide material enriched with elemental gold is obtained.

2. The method of claim 1, wherein the method is characterized by, In step S2, the concentration of the glycine is 0.5-2 mol / L.

3. The method of claim 1, wherein the method is characterized by, In step S2, the concentration of the potassium permanganate is 0.05-0.2 mol / L.

4. The method of claim 1, wherein the method is characterized by, In step S2, the stirring reaction is performed for 30-60 min.

5. The method of claim 1, wherein the method is characterized by, The electronic waste comprises at least one of waste circuit boards, integrated chips, and waste electrode materials.

6. The method of claim 1, wherein the method is characterized by, During the grinding, the electronic waste is ground to a particle size of less than 100 mesh, and the content of the electronic waste accounts for 95%-98% of the total mass of the ground powder.

7. The method of claim 1, wherein the method is characterized by, The mass concentration of the slurry is 10%-30%.

8. The method of claim 1, wherein the method is characterized by, The pH value of the slurry is adjusted by adding a pH value adjusting agent; the pH value adjusting agent is sodium hydroxide.

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