An organic semiconductor photocatalytic material, a preparation method thereof and a method for recovering silver from a crystalline silicon photovoltaic module using the same

Abstract

The application provides an organic semiconductor photocatalytic material and a preparation method thereof and a method for recovering silver from a crystalline silicon photovoltaic module, and relates to the technical field of waste solar device recycling. Raw materials of the organic semiconductor photocatalytic material include: melamine 0.3-1 g, vitamin B3 compounds 60-100 mg, and water 40-60 g; the vitamin B3 compounds include one of nicotinic acid and nicotinamide. The organic semiconductor photocatalytic material, the preparation method thereof and the method for recovering silver from the crystalline silicon photovoltaic module are synthesized through a supramolecular self-assembly strategy, the use of a highly toxic reagent is avoided in the silver recovery process, and energy consumption is reduced, and the method has the advantages of environmental friendliness, low energy consumption and high product selectivity.

Description

Technical Field

[0001] This application relates to the field of recycling technology for waste solar energy devices, and more particularly to an organic semiconductor photocatalytic material, its preparation method, and a method for recovering silver from crystalline silicon photovoltaic modules using the same. Background Technology

[0002] As photovoltaic (PV) modules worldwide approach the end of their service life, the demand for efficient and environmentally friendly recycling technologies for the precious metal silver in retired PV modules is increasingly prominent. PV modules contain a large amount of silver electrodes, whose recycling value is significant, but existing recycling technologies face numerous challenges. Current mainstream silver recycling processes, especially traditional methods such as cyanidation and pyrometallurgical refining, have significant technical limitations and environmental risks. First, there is a high risk of environmental pollution: the cyanidation method uses highly toxic cyanide as a leaching agent, and its process wastewater typically has a chemical oxygen demand (COD) exceeding 2000 mg / L, posing serious environmental safety risks and incurring high treatment costs. Second, energy consumption is enormous: pyrometallurgical refining processes are extremely energy-intensive, reportedly reaching approximately 600 kWh / kg of silver, and have lengthy process cycles, typically exceeding 12 hours, which is inconsistent with current energy conservation and emission reduction trends. Third, product selectivity is poor: traditional methods have limited separation effects on coexisting metals (such as copper and lead), resulting in impurity metal residues in the recovered silver often exceeding 5%, significantly affecting the purity of the final silver product and its subsequent application performance. In addition, these traditional methods have high equipment requirements and harsh operating conditions, making it difficult to achieve large-scale application.

[0003] Photocatalysis technology has shown promise in the field of precious metal recycling due to its advantages such as mild reaction conditions and good environmental compatibility. However, existing photocatalytic materials still suffer from problems such as narrow light response range, low catalytic efficiency, and poor stability in silver recycling applications. Especially when processing photovoltaic module waste with complex components, the selectivity and catalytic activity of existing photocatalytic materials often fail to meet practical requirements. Therefore, developing novel, efficient, and environmentally friendly photocatalytic materials and applying them to the recovery of silver from photovoltaic modules has significant scientific and practical value. Summary of the Invention

[0004] The purpose of this application is to provide an organic semiconductor photocatalytic material, a method for preparing the same, and a method for recovering silver from crystalline silicon photovoltaic modules using the same, in order to solve the above-mentioned problems.

[0005] To achieve the above objectives, this application adopts the following technical solution: This application provides an organic semiconductor photocatalytic material, which is synthesized by a supramolecular self-assembly strategy. The raw materials include: 0.3-1g of melamine, 60-100mg of vitamin B3 compounds, and 40-60g of water. The vitamin B3 compounds include one of niacin and niacinamide.

[0006] This application also provides a method for preparing the organic semiconductor photocatalytic material, comprising: The melamine and the vitamin B3 compound are mixed with water and reacted. The reaction product is separated, washed, and dried to obtain an intermediate. The intermediate is then calcined to obtain the organic semiconductor photocatalytic material.

[0007] Optionally, the mixing includes magnetic stirring dispersion.

[0008] Optionally, the magnetic stirring dispersion is performed at a speed of 1000-1500 rpm for 3-5 minutes.

[0009] Optionally, the reaction temperature is 500-600℃ and the time is 60-90 minutes.

[0010] Optionally, the separation includes centrifugal separation.

[0011] Optionally, the centrifugation speed is 600-800 rpm and the time is 2-3 minutes.

[0012] Optionally, the calcination heating rate is 2-5℃ / min, the final temperature is 550-600℃, and the time is 4-8 hours.

[0013] This application also provides a method for recovering silver from crystalline silicon photovoltaic modules, including: The crystalline silicon photovoltaic module is crushed and sorted to obtain silver-containing silicon-based material; the silver-containing silicon-based material is mixed with a leaching reagent and subjected to a leaching reaction to obtain a leachate; the leachate is mixed with the organic semiconductor photocatalytic material and subjected to a photocatalytic reduction reaction to obtain a mixture; the mixture is then separated into solid and liquid phases to obtain elemental silver.

[0014] Optionally, the particle size of the crystalline silicon photovoltaic module after pulverization is 1-2 mm.

[0015] Optionally, the sorting includes sequential magnetic separation and eddy current separation.

[0016] Optionally, the leaching agent includes Na2S2O3.

[0017] Optionally, the leaching reaction conditions are: a temperature of 20-40°C and a time of 30-50 min.

[0018] Optionally, the conditions for the photocatalytic reduction reaction are as follows: a 400 nm filter and a 300 W xenon lamp are used as the light source, and the reactor is a sealed glass reaction vessel.

[0019] Compared with the prior art, the beneficial effects of this application include: The organic semiconductor photocatalytic material, its preparation method, and the method for recovering silver from crystalline silicon photovoltaic modules provided in this application, through a supramolecular self-assembly strategy, synthesizes photocatalytic materials and combines them with specific process parameters. This avoids the use of highly toxic reagents and reduces energy consumption during the silver recovery process, and has the advantages of being environmentally friendly, having low energy consumption, and high product selectivity. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0021] Figure 1 This is a schematic diagram of the process flow for preparing organic semiconductor photocatalytic materials in an example. Figure 2 This is a schematic diagram of the energy band structure of the organic semiconductor photocatalytic material prepared in Example 1. Detailed Implementation

[0022] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0023] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0024] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0025] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0026] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0027] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0028] To better illustrate the technical solution provided in this application, the technical solution will be described in its entirety before proceeding with specific implementation methods.

[0029] In existing technologies, the photovoltaic module recycling field has long relied on cyanidation and pyrometallurgical refining processes for silver recovery. These methods suffer from high environmental pollution risks, high energy consumption, and low product purity. Cyanidation uses highly toxic reagents, making wastewater treatment difficult, while pyrometallurgical processes are excessively energy-intensive and struggle to effectively separate impurity metals, thus hindering the sustainable development of silver recovery technology. In the crystalline silicon photovoltaic module recycling scenario, traditional methods struggle to achieve efficient and selective silver recovery under mild conditions, necessitating the development of new, environmentally friendly processes.

[0030] To address these issues, research has focused on finding environmentally friendly alternative technologies. Photocatalytic reduction reactions have attracted attention due to their low energy consumption and pollution-free characteristics, but conventional photocatalysts suffer from drawbacks such as low charge separation efficiency and insufficient active sites. By analyzing the supramolecular self-assembly principle, it was discovered that certain organic molecules can construct ordered structures through hydrogen bond networks, which is beneficial for the transport of photogenerated charge carriers. Further research revealed that the combination of nitrogen-containing heterocyclic compounds and vitamin B3 derivatives may form semiconductor materials with optimized band structures, providing a suitable reaction environment for silver ion reduction.

[0031] Therefore, this application proposes a supramolecular self-assembly strategy to prepare organic semiconductor photocatalytic materials. These materials are composites with specific microstructures formed by mixing melamine, vitamin B3 compounds, and water in a specific ratio, followed by a reaction and calcination. Melamine, as a nitrogen-rich precursor, has amino groups that can form hydrogen bond networks with vitamin B3 compounds, constructing a three-dimensional porous framework structure. The vitamin B3 compounds contain carboxylic acid or amide functional groups, which act as structure-directing agents to regulate molecular arrangement and as electron donors in the photocatalytic reaction during self-assembly. Water, as the reaction medium, generates porous structures through evaporation during the high-temperature treatment stage, increasing the specific surface area of ​​the material.

[0032] In a first aspect, this application provides an organic semiconductor photocatalytic material, the raw materials of which include: 0.3-1g of melamine, 60-100mg of vitamin B3 compounds, and 40-60g of water; The vitamin B3 compounds include one of niacin and niacinamide.

[0033] Optionally, the amount of melamine can be 0.3g, 0.4g, 0.5g, 0.6g, 0.7g, 0.8g, 0.9g, 1.0g, or any value between 0.3g and 1.0g; the amount of vitamin B3 compounds can be 60mg, 65mg, 70mg, 75mg, 80mg, 85mg, 90mg, 95mg, 100mg, or any value between 60mg and 100mg; and the amount of water can be 40g, 42g, 44g, 46g, 48g, 50g, 52g, 54g, 56g, 58g, 60g, or any value between 40mg and 60g.

[0034] Specifically, melamine and vitamin B3 compounds form a supramolecular complex in an aqueous environment through hydrogen bonding. This complex undergoes intermolecular condensation during calcination, generating a semiconductor material with a conjugated π-electron system. During preparation, the six-membered ring structure of melamine provides a rigid framework for the material, while the polar groups of vitamin B3 enhance the hydrophilicity of the material surface, facilitating reactant adsorption. The resulting hierarchical porous structure not only provides ample active sites but also shortens the migration path of photogenerated carriers, enhancing photocatalytic reduction capabilities.

[0035] Secondly, this application provides a method for preparing the organic semiconductor photocatalytic material, comprising: The melamine and the vitamin B3 compound are mixed with water and reacted. The reaction product is separated, washed, and dried to obtain an intermediate. The intermediate is then calcined to obtain the organic semiconductor photocatalytic material.

[0036] Specifically, melamine and vitamin B3 compounds form a supramolecular precursor in an aqueous environment through intermolecular hydrogen bonds and π-π stacking interactions. After heat treatment, this precursor is transformed into a semiconductor material with photocatalytic activity. No organic solvents or surfactants are required during the preparation process. Centrifugation effectively removes unreacted substances from the reaction products, and subsequent calcination treatment forms a regular layered structure, enhancing carrier migration capabilities.

[0037] Compared to existing technologies, traditional photocatalyst preparation often involves complex template methods or high-temperature vapor deposition processes, requiring the use of noble metal catalysts or vacuum equipment. This method, through supramolecular self-assembly combined with calcination, enables the construction of semiconductor structures in an ambient-pressure aqueous environment, avoiding the use of toxic reagents and significantly reducing equipment requirements. While existing technologies involve stepwise material synthesis and structure control, this approach organically combines molecular self-assembly with thermal conversion processes, achieving simultaneous optimization of material morphology and band structure.

[0038] The preparation method provided in this application can effectively construct semiconductor materials with visible light response. Their layered structure provides ample active sites for silver ion adsorption and reduction. The aqueous reaction system avoids organic solvent contamination during preparation, and the calcination temperature is reduced by approximately 200°C compared to traditional pyrometallurgical processes, significantly reducing energy consumption. The resulting material exhibits high selectivity in silver recovery applications and can suppress the co-deposition of metals such as copper and lead.

[0039] In an alternative implementation, the mixing includes magnetic stirring dispersion.

[0040] In one optional embodiment, the magnetic stirring dispersion is performed at a speed of 1000-1500 rpm for 3-5 minutes.

[0041] Optionally, the magnetic stirring speed can be 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm, 1400 rpm, 1450 rpm, 1500 rpm, or any value between 1000 and 1500 rpm; the magnetic stirring time can be 3 minutes, 4 minutes, 5 minutes, or any value between 3 and 5 minutes.

[0042] Magnetic stirring dispersion refers to the process of mixing solids and liquids by rotating a stir bar driven by magnetic force. This can be achieved using constant or variable speed modes. Its function is to promote uniform dispersion of raw materials by controlling mechanical shear force, preventing agglomeration. Rotation speed refers to the number of revolutions the stirring rotor makes per minute, which can be adjusted by changing the power setting of the magnetic stirrer. Its function is to balance mixing efficiency and energy consumption, ensuring the reaction system reaches dynamic equilibrium.

[0043] Specifically, during the mixing of melamine, vitamin B3 compounds, and water, a magnetic stirrer applies mechanical force at a specific rotation speed, causing solid particles to form a stable suspension in the liquid phase. The eddies generated by the stirrer effectively break up particle aggregates, resulting in a uniformly dispersed system. This process avoids the uneven dispersion problems associated with traditional manual stirring, laying the foundation for subsequent high-temperature calcination to form homogeneous semiconductor materials.

[0044] The aforementioned techniques enable efficient dispersion of reactants in the liquid phase, effectively reducing agglomeration and thus increasing the specific surface area and active site density of the final photocatalytic material. The control methods are simple to operate and highly reproducible, providing a reliable guarantee for the large-scale production of high-quality organic semiconductor materials.

[0045] In one optional embodiment, the reaction is carried out at a temperature of 500-600°C for 30-50 minutes.

[0046] Optionally, the reaction temperature can be 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, or any value between 500℃ and 600℃; the reaction time can be 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, or any value between 30 and 50 minutes.

[0047] In one alternative implementation, the separation includes centrifugal separation.

[0048] In one optional embodiment, the centrifugation separation is performed at a speed of 600-800 rpm for 2-3 minutes.

[0049] Optionally, the centrifugation speed can be 600 rpm, 610 rpm, 620 rpm, 630 rpm, 640 rpm, 650 rpm, 660 rpm, 670 rpm, 680 rpm, 690 rpm, 700 rpm, 710 rpm, 720 rpm, 730 rpm, 740 rpm, 750 rpm, 760 rpm, 770 rpm, 780 rpm, 790 rpm, or 800 rpm, or any value between 600 and 800 rpm; the centrifugation time can be 2 minutes, 3 minutes, or any value between 2 and 3 minutes.

[0050] In one optional embodiment, the calcination heating rate is 2-5°C / min, the final temperature is 550-600°C, and the time is 4-8 hours.

[0051] Optionally, the heating rate of calcination can be 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, or any value between 2 and 5℃ / min; the endpoint temperature can be 550℃, 555℃, 560℃, 565℃, 570℃, 575℃, 580℃, 585℃, 590℃, 595℃, 600℃, or any value between 550 and 600℃; the calcination time can be 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, or any value between 4 and 8 hours.

[0052] Specifically, the calcination process begins with a slow heating to 550-600°C at a rate of 2-5°C per minute. During this process, the organic components in the precursor gradually remove volatile substances and form a conjugated structure. Subsequently, the temperature is maintained at the target temperature for 4-8 hours, for example, using an isothermal mode, to allow the carbon skeleton to fully cross-link, ultimately forming a semiconductor material with a regular porous structure and surface active sites.

[0053] Through the aforementioned technical means, effective control of lattice defects in semiconductor materials was achieved, thereby improving the migration efficiency of photogenerated carriers. In silver recovery applications, this material exhibits more stable photocatalytic activity, capable of continuously reducing silver ions under mild conditions while avoiding catalyst deactivation problems caused by high-temperature processes.

[0054] Thirdly, this application also provides a method for recovering silver from crystalline silicon photovoltaic modules, comprising: The crystalline silicon photovoltaic module is crushed and sorted to obtain silver-containing silicon-based material; the silver-containing silicon-based material is mixed with a leaching reagent and subjected to a leaching reaction to obtain a leachate; the leachate is mixed with the organic semiconductor photocatalytic material and subjected to a photocatalytic reduction reaction to obtain a mixture; the mixture is then separated into solid and liquid phases to obtain elemental silver.

[0055] Specifically, after the solar cells are crushed into uniform particles, the iron-based material is removed by magnetic separation, and then the silver-containing silicon-based material is separated by eddy current separation. The silver-containing material reacts with the leaching reagent under heating conditions, and silver enters the solution in ionic form. After the leachate is mixed with the photocatalytic material, an electron transfer reaction occurs under light irradiation, and the silver ions are reduced to elemental silver particles. Finally, solid-liquid separation is achieved by centrifugation or filtration.

[0056] The method for recovering silver from crystalline silicon photovoltaic modules provided in this application solves the problems of severe environmental pollution from cyanide methods, excessive energy consumption from pyrometallurgical methods, and low purity of products from traditional processes, achieving efficient silver recovery. The photocatalytic reduction reaction avoids the use of toxic reagents and reduces the difficulty of wastewater treatment; the synergistic effect of sorting and leaching steps improves the silver recovery rate; and high-purity elemental silver can be directly obtained after solid-liquid separation without additional refining steps.

[0057] In one optional embodiment, the particle size of the crystalline silicon photovoltaic module after pulverization is 1-2 mm.

[0058] Optionally, the particle size of the pulverized crystalline silicon photovoltaic module can be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, or any value between 1.0 and 2.0 mm.

[0059] In an optional implementation, the sorting includes sequential magnetic separation and eddy current separation.

[0060] In an optional embodiment, the leaching agent comprises Na2S2O3.

[0061] In one optional embodiment, the leaching reaction is carried out under the following conditions: a temperature of 20-40°C and a time of 30-50 min.

[0062] Optionally, the leaching reaction temperature can be 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, or any value between 20℃ and 50℃; the leaching reaction time can be 30 min, 36 min, 40 min, 45 min, 50 min, or any value between 30 min and 50 min.

[0063] In one optional embodiment, the photocatalytic reduction reaction is performed using a 400 nm filter and a 300 W xenon lamp as the light source. The reactor is a sealed glass reaction vessel.

[0064] Specifically, when the solar cells are broken down to a particle size of 1-2 mm, their increased specific surface area improves the efficiency of metal identification in subsequent sorting processes. Magnetic separation effectively removes ferromagnetic impurities, while eddy current separation separates silver-containing components based on differences in metal conductivity. The leaching reagent undergoes a complexation reaction with silver under specific temperature and time conditions, forming a soluble silver complex that enters the solution phase. The photocatalyst generates electron-hole pairs under light excitation; electrons migrate to the surface of silver ions, causing them to be reduced to elemental silver, while holes are consumed by a sacrificial agent to prevent the reverse reaction from occurring.

[0065] Compared to existing technologies, traditional processes using sodium cyanide as a leaching agent require operation under high-temperature, strongly alkaline conditions. This solution, however, utilizes a thiourea-sulfuric acid system, enabling leaching under acidic conditions at room temperature, significantly reducing equipment corrosion risks. Existing sorting processes often employ single magnetic separation, which is insufficient for separating non-ferrous metals. This solution enhances the separation of metals such as copper and aluminum through eddy current separation. Compared to traditional pyrometallurgical refining, which requires maintaining temperatures above 800℃, photocatalytic reduction can achieve silver reduction and deposition at room temperature, reducing energy consumption by approximately 60%.

[0066] The method for recovering silver from crystalline silicon photovoltaic modules provided in this application effectively solves the technical defects of traditional processes, such as high toxicity of leaching agents, low sorting efficiency, and high energy consumption. Particle size control improves material processing efficiency, the composite sorting process increases the silver recovery rate to over 98%, the environmentally friendly leaching reagent avoids the generation of cyanide-containing wastewater, and the efficient photocatalytic reduction reaction at room temperature shortens the silver recovery cycle, obtaining high-purity elemental silver.

[0067] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0068] Example 1 This embodiment provides an organic semiconductor photocatalytic material: Its raw materials include: 0.8g melamine, 80mg nicotinamide, and 50g water.

[0069] This embodiment also provides a method for preparing the organic semiconductor photocatalytic material, the process flow of which is as follows: Figure 1 As shown, the specific steps are as follows: Melamine 0.8g, nicotinamide 80mg, and water 50g were magnetically stirred and dispersed for 3 minutes at 1000 rpm, and then reacted at 70℃ for 80 minutes to obtain the reaction product.

[0070] The reaction product was centrifuged at 600 rpm for 2 minutes, and then washed and dried to obtain the intermediate.

[0071] The intermediate was heated to 600°C at a heating rate of 3°C / min and calcined for 5 hours to obtain an organic semiconductor photocatalytic material.

[0072] A schematic diagram of the energy band structure of the prepared organic semiconductor photocatalytic material is shown below. Figure 2 As shown, the conduction band value is -1.06, indicating extremely strong Ag. + Restorative ability.

[0073] This embodiment also provides a method for recovering silver from crystalline silicon photovoltaic modules, the specific steps of which are as follows: Crystalline silicon photovoltaic modules are crushed into 1mm particles; these particles are then subjected to magnetic separation and eddy current separation to obtain silver-containing silicon-based materials. Magnetic separation is performed using a permanent magnet drum to remove ferromagnetic materials; eddy current separation is achieved by generating eddy currents on non-ferrous metal surfaces using an alternating magnetic field to remove copper and aluminum.

[0074] The silver-containing silicon-based material was mixed with Na2S2O3 and leached at 30°C for 40 minutes to obtain a leachate. The leachate was then mixed with the prepared organic semiconductor material at a ratio of 10:1 and placed in a photocatalytic reactor for photocatalytic reduction. The resulting mixture was filtered and weighed to record the amount of silver reduced.

[0075] Example 2 This embodiment provides an organic semiconductor photocatalytic material: Its raw materials include: 0.8g melamine, 80mg nicotinamide, and 60g water.

[0076] This embodiment also provides a method for preparing the organic semiconductor photocatalytic material, the specific steps of which are as follows: Melamine 0.8g, nicotinamide 80mg, and water 50g were magnetically stirred and dispersed for 3 minutes at 1000 rpm, and then reacted at 70℃ for 80 minutes to obtain the reaction product.

[0077] The reaction product was centrifuged at 600 rpm for 2 minutes, and then washed and dried to obtain the intermediate.

[0078] The intermediate was heated to 600°C at a heating rate of 3°C / min and calcined for 5 hours to obtain an organic semiconductor photocatalytic material.

[0079] This embodiment also provides a method for recovering silver from crystalline silicon photovoltaic modules, the specific steps of which are as follows: Crystalline silicon photovoltaic modules are crushed into 1mm particles; these particles are then subjected to magnetic separation and eddy current separation to obtain silver-containing silicon-based materials. Magnetic separation is performed using a permanent magnet drum to remove ferromagnetic materials; eddy current separation is achieved by generating eddy currents on non-ferrous metal surfaces using an alternating magnetic field to remove copper and aluminum.

[0080] The silver-containing silicon-based material was mixed with Na2S2O3 and leached at 30°C for 40 minutes to obtain a leachate. The leachate was then mixed with the prepared organic semiconductor material at a ratio of 10:1 and placed in a photocatalytic reactor for photocatalytic reduction. The resulting mixture was filtered and weighed to record the amount of silver reduced.

[0081] Example 3 This embodiment provides an organic semiconductor photocatalytic material: Its raw materials include: 0.5g melamine, 80mg nicotinic acid, and 50g water.

[0082] This embodiment also provides a method for preparing the organic semiconductor photocatalytic material, the specific steps of which are as follows: 0.5g of melamine, 80mg of nicotinic acid, and 50g of water were magnetically stirred and dispersed for 3 minutes at 1000 rpm, and then reacted at 70℃ for 80 minutes to obtain the reaction product.

[0083] The reaction product was centrifuged at 600 pm for 3 minutes, and then washed and dried to obtain the intermediate.

[0084] The intermediate was heated to 600°C at a heating rate of 3°C / min and calcined for 5 hours to obtain an organic semiconductor photocatalytic material.

[0085] This embodiment also provides a method for recovering silver from crystalline silicon photovoltaic modules, the specific steps of which are as follows: Crystalline silicon photovoltaic modules are crushed into 1mm particles; these particles are then subjected to magnetic separation and eddy current separation to obtain silver-containing silicon-based materials. Magnetic separation is performed using a permanent magnet drum to remove ferromagnetic materials; eddy current separation is achieved by generating eddy currents on non-ferrous metal surfaces using an alternating magnetic field to remove copper and aluminum.

[0086] The silver-containing silicon-based material was mixed with Na2S2O3 and leached at 30°C for 40 minutes to obtain a leachate. The leachate was then mixed with the prepared organic semiconductor material at a ratio of 10:1 and placed in a photocatalytic reactor for photocatalytic reduction. The resulting mixture was filtered and weighed to record the amount of silver reduced.

[0087] Comparative Example 1 This comparative example provides a conventional cyanide method for recovering silver, with the following specific steps: Crystalline silicon photovoltaic modules were crushed into 1mm particles and added to sodium cyanide and sodium hydroxide for leaching at 30°C in an oxygen atmosphere for 24 hours. After filtration, a solution containing [Ag(CN)2] was obtained. - The precious liquor was deoxidized under absolute pressure using a zinc powder displacement method, so that the dissolved oxygen content of the deoxidized liquor was no more than 1 ppm. After filtration again, a precipitate containing silver and zinc was obtained. The precipitate was washed with dilute sulfuric acid to obtain crude silver powder, which was then melted, cast, and weighed to record the amount of silver reduced in grams.

[0088] Comparative Example 2 This comparative example provides a conventional method for recovering silver through pyrometallurgical refining, with the specific steps as follows: The crystalline silicon photovoltaic modules are crushed and loaded into an induction furnace, where they are heated to 1100°C. Air or oxygen is blown into the molten metal to preferentially oxidize impurity metals (mainly copper), which then separate as slag. Once the metal is completely melted, air or pure oxygen is blown into the depths of the melt through an oxidation-resistant lance (such as an iron pipe). When the oxidation process reaches its later stages and the copper content in the melt is low, potassium nitrate (KNO3) is sprinkled onto the surface of the melt as a strong oxidant to oxidize any remaining copper. Finally, the purified high-purity silver melt is recast and the recovered weight is recorded.

[0089] Comparative Example 3 This comparative example demonstrates the use of graphitic carbon nitride purchased from the market (from Xianfeng Nano) as a photocatalyst for silver recovery. The specific steps are as follows: Crystalline silicon photovoltaic modules are crushed into 1mm particles; these particles are then subjected to magnetic separation and eddy current separation to obtain silver-containing silicon-based materials. Magnetic separation is performed using a permanent magnet drum to remove ferromagnetic materials; eddy current separation is achieved by generating eddy currents on non-ferrous metal surfaces using an alternating magnetic field to remove copper and aluminum.

[0090] The silver-containing silicon-based material was mixed with Na2S2O3 and leached at 30°C for 40 minutes to obtain a leachate. The leachate was then mixed with the prepared organic semiconductor material at a ratio of 10:1 and placed in a photocatalytic reactor for photocatalytic reduction. The resulting mixture was filtered and weighed to record the amount of silver reduced.

[0091] Table 1 shows the results of the methods for recovering silver from crystalline silicon photovoltaic modules provided in the examples and comparative examples.

[0092] Table 1. Experimental results of the examples and comparative examples.

[0093] As shown in Table 1, silver recovery using cyanidation and pyrometallurgical refining processes presents challenges such as high environmental pollution risks, high energy consumption, and low product purity. Cyanidation uses highly toxic reagents, leading to difficult wastewater treatment, while pyrometallurgical processes are energy-intensive and struggle to effectively separate impurity metals. Examples 1-3 demonstrate that the technical solution provided in this application has low energy consumption and low pollution characteristics. Compared to Comparative Example 3, the organic semiconductor photocatalytic material provided in this application, through supramolecular self-assembly, reveals that specific organic molecules can construct ordered structures via hydrogen bond networks, which is beneficial for the transport of photogenerated charge carriers; therefore, the overall silver recovery rate is also higher.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0095] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. An organic semiconductor photocatalytic material, characterized in that, Its raw materials include: 0.3-1g of melamine, 60-100mg of vitamin B3 compounds, and 40-60g of water; The vitamin B3 compounds include one of niacin and niacinamide.

2. A method for preparing the organic semiconductor photocatalytic material according to claim 1, characterized in that, include: The melamine and the vitamin B3 compound are mixed with water and reacted. The reaction product is separated, washed, and dried to obtain an intermediate. The intermediate is then calcined to obtain the organic semiconductor photocatalytic material.

3. The method for preparing the organic semiconductor photocatalytic material according to claim 2, characterized in that, The mixing includes magnetic stirring dispersion.

4. The method for preparing the organic semiconductor photocatalytic material according to claim 3, characterized in that, The magnetic stirring and dispersion is performed at a speed of 1000-1500 rpm for 3-5 minutes.

5. The method for preparing the organic semiconductor photocatalytic material according to claim 2, characterized in that, The reaction is carried out at a temperature of 500-600℃ for 60-90 minutes.

6. The method for preparing the organic semiconductor photocatalytic material according to claim 2, characterized in that, The separation includes centrifugal separation.

7. The method for preparing the organic semiconductor photocatalytic material according to claim 6, characterized in that, The centrifugation speed is 600-800 rpm, and the time is 2-3 minutes.

8. The method for preparing the organic semiconductor photocatalytic material according to any one of claims 2-7, characterized in that, The calcination process involves a heating rate of 2-5°C / minute, an endpoint temperature of 550-600°C, and a duration of 4-8 hours.

9. A method for recovering silver from crystalline silicon photovoltaic modules, characterized in that, include: The crystalline silicon photovoltaic module is crushed and sorted to obtain silver-containing silicon-based material; the silver-containing silicon-based material is mixed with a leaching reagent and subjected to a leaching reaction to obtain a leachate; the leachate is mixed with the organic semiconductor photocatalytic material of claim 1 and subjected to a photocatalytic reduction reaction to obtain a mixture; the mixture is subjected to solid-liquid separation to obtain elemental silver.

10. The method for recovering silver from crystalline silicon photovoltaic modules according to claim 9, characterized in that, At least one of the following conditions must be met: A. The particle size of the crystalline silicon photovoltaic module after the aforementioned crushing is 1-2 mm; B. The sorting includes sequential magnetic separation and eddy current separation; C. The leaching reagent includes Na2S2O3; D. The leaching reaction conditions are: temperature 20-40℃ and time 30-50min; E. The mass ratio of the leachate to the organic semiconductor photocatalytic material is 10:1; F. The conditions for the photocatalytic reduction reaction are as follows: a 400 nm filter and a 300 W xenon lamp are used as the light source, and the reactor is a sealed glass reaction vessel.

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