Method for preparing silver ingot from photovoltaic welding strip

Abstract

The invention relates to the technical field of silver smelting, in particular to a method for preparing a silver ingot from a photovoltaic welding strip, which comprises the following steps of: (a) mechanically crushing the photovoltaic welding strip to obtain a crushed material; (b) desiliconizing the crushed material to obtain a desiliconized material; (c) grinding the desiliconized material until the particle size is 0.1-0.5 mm to obtain a pretreated desiliconized material; (d) a flotation agent is added into the pretreated desilicication material for flotation separation, and silver-enriched concentrate is obtained; (e) drying the silver-enriched concentrate, and performing zone-melting purification to obtain high-purity silver bars; and (f) melting, casting and cooling the high-purity silver bar to obtain a finished product silver ingot. According to the scheme, the technologies of magnetic separation, flotation and zone melting are combined, and preparation of high-recovery-rate and high-purity silver ingots is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of silver smelting, and in particular to a method for preparing silver ingots from photovoltaic welding ribbons. Background Art

[0002] With the rapid development of the photovoltaic industry, the recycling of photovoltaic ribbon, a key component of solar cell modules, has become a research hotspot. PV ribbon contains a high proportion of silver. Efficiently and environmentally friendly recovery of silver from this material and its production into high-purity silver ingots remains a pressing technical challenge. However, existing silver recovery technologies remain deficient in terms of specificity, efficiency, and environmental friendliness, making it difficult to fully meet the photovoltaic industry's demand for silver resource recycling. Patent publication number CN102660684B discloses a method for purifying silver and producing high-purity silver nitrate from wastewater from a rhinestone silver plating production line. This method provides a technical solution for extracting crude silver from silver plating wastewater and further purifying it to produce high-purity silver nitrate. This method achieves efficient recovery and reuse of precious metal silver, but it is targeted at silver recovery from silver plating wastewater, not the specific treatment of photovoltaic ribbon. Because the bonding between the substrate and the silver layer in photovoltaic ribbon differs significantly from the silver morphology in silver plating wastewater, this method cannot be directly applied to the efficient separation and purification of silver from photovoltaic ribbon. Furthermore, this technical solution primarily focuses on the preparation of silver nitrate and does not address the preparation process for silver ingots, making it difficult to meet the direct demand for silver ingots in the photovoltaic industry. Another patent, CN116904758B, discloses a method for recovering precious metals from silver-containing copper slag in conjunction with spent automotive catalysts. Through multi-metal smelting, capture, and vacuum distillation, this method achieves the comprehensive recovery of valuable elements from silver-containing copper slag and spent automotive catalysts, particularly the efficient enrichment of silver, gold, and platinum group metals. However, this technical solution primarily addresses the treatment of complex mixtures such as silver-containing copper slag and automotive catalysts, failing to fully consider the close bonding of silver in photovoltaic ribbons with other substrates (such as copper or tin). Silver in photovoltaic ribbons typically exists as a coating, requiring specific separation steps for efficient recovery. This method can reduce recovery efficiency due to differences in material properties. Furthermore, this technical solution focuses on the enrichment and initial refining of precious metals and does not provide a specific process for preparing silver ingots, making it difficult to meet the photovoltaic industry's demand for high-purity silver ingots.

[0003] These issues indicate that existing silver recovery technologies for photovoltaic ribbon processing suffer from insufficient specificity, low recovery efficiency, and a lack of silver ingot preparation technology. Therefore, developing a silver recovery technology specifically for photovoltaic ribbon processing is particularly important. Summary of the Invention

[0004] In response to the above problems, the present invention proposes a method for preparing silver ingots from photovoltaic welding ribbons. By controlling the particle size and combining magnetic separation, flotation and zone melting techniques, the preparation of high-recovery and high-purity silver ingots is achieved.

[0005] The technical solution adopted by the present invention to solve its technical problem is: A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of ≤5 mm using a hammer crusher or a shear crusher, and magnetically separating the ribbon to remove iron impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 10% to 15% in a mass ratio of 1:2 to 3, stirring and reacting at 80° C. and 100 rpm for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7 to 8 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.1-0.5 mm using a ball mill or a rod mill at a rotation speed of 200-300 r / min for 15-20 min, mainly to achieve the desired particle size, and then screening out coarse particles larger than 0.5 mm through a vibrating screen to obtain a pretreated desiliconized material; The particle size of the pre-treated desiliconized material in step (c) is ≤ 0.5 mm, ensuring that at least D 90 When the particle size is ≤0.5mm, the silver flotation recovery rate can reach over 98%; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.8-1.2g of dodecylamine, 0.4-0.6g of terpineol, and 8-12g of water added to every 100g of the pretreated desiliconized material; mechanical stirring is performed in a flotation tank at a speed of 150-200r / min to ensure full contact between the flotation agent and the material; the dodecylamine collector has a surface adsorption efficiency of ≥90% on silver particles within a particle size range of 0.1-0.5mm; the flotation agent of this embodiment is a mixture of the above three substances; In step (d), the mechanical stirring speed of the flotation tank is 150-200 r / min, which is suitable for the effective attachment of particles with a particle size of 0.1-0.5 mm to the bubbles. The particle size of the desiliconized material is controlled to 0.1-0.5 mm through the grinding and screening process, aiming to solve the problem of difficult bubble attachment to coarse particles (>1 mm) and easy agglomeration of fine particles (<0.01 mm), thereby improving the attachment efficiency of silver particles and bubbles during the flotation process. Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing it in a zone melting furnace with the temperature controlled at 960° C. to 1000° C., the melting zone length at 10 to 15 mm, and the moving speed at 12 mm / min for zone melting purification to obtain high-purity silver bars; Step (f) melting a high-purity silver bar at a melting temperature of 1050° C. to 1100° C., introducing argon gas as a protective gas during the melting process, adding a borax solution with a mass concentration of 0.1% to 0.2% in an amount of 0.5-0.8 mL per 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0006] The core mechanism of this solution is to achieve efficient silver extraction and purification through the synergistic action of multiple steps. First, photovoltaic ribbon (containing silver, copper, silicon, and other components) is mechanically crushed to a particle size of ≤5mm, and magnetic separation is used to remove iron impurities, providing a clean material base for subsequent reactions. Alkaline desiliconization with sodium hydroxide solution is then performed. Silicon reacts with strong alkali to form soluble sodium silicate, selectively removing silicon-based impurities while retaining silver due to its chemical stability. The desiliconized material is separated by flotation. Dodecylamine is used as a collector to adsorb the surface of silver particles, making them hydrophobic. Terpineol is used as a frother to stabilize the foam layer, causing the silver particles to float with the bubbles to form an enriched concentrate, thereby separating the silver from other metals (such as copper) and non-metallic impurities. To further improve the silver purity, the enriched concentrate is zone-melted. By controlling the temperature, length, and movement speed of the melt zone, residual metallic impurities such as copper and zinc are gradually removed, leveraging the differences in the segregation coefficients of impurities in the solid-liquid phase. Finally, the high-purity silver bars are melted and cast, and the finished silver ingots are obtained after cooling. Each step is closely linked to each other, from pretreatment, impurity removal, separation to purification, which progresses layer by layer. The system solves the problems of low silver recovery efficiency and insufficient purity in photovoltaic welding ribbons.

[0007] The coarse particles >0.5 mm screened out in step (c) are mainly composed of undissociated copper or solder strip matrix and can be recycled as secondary metal materials.

[0008] Compared with existing technologies, the advantages of this solution are: 1. This process design, based on the compositional characteristics of photovoltaic ribbon, achieves efficient silver recovery and purification through multi-step coordinated optimization. The pretreatment stage removes iron impurities, laying a clean foundation for subsequent reactions. Alkaline desiliconization utilizes a strong base to selectively dissolve silicon-based components, preventing chemical corrosion of the silver due to its inertness. Flotation utilizes a combination of reagents to efficiently separate silver particles from impurities. Zone melting purification utilizes differential solid-liquid coagulation for further purification. These steps are interconnected, forming a complete closed loop of impurity removal, enrichment, and refining, systematically addressing the low silver recovery efficiency and insufficient purity issues inherent in traditional processes.

[0009] 2. The reagents selected for this scheme take into account both specificity and environmental friendliness, precisely adapting to the separation requirements of the target components. When used for desiliconization, sodium hydroxide solution only dissolves silicon-based impurities and does not react with silver, thus avoiding silver loss. The flotation agent, a combination of dodecylamine and terpineol, selectively adsorbs the surface of silver particles, making them hydrophobic and stabilizing the foam layer to improve enrichment efficiency. Borax acts as a refining agent during the melting stage, assisting in the removal of residual impurities without producing harmful byproducts. The reagents throughout the entire process are environmentally friendly and low-cost, ensuring high silver recovery and purity while reducing the risk of secondary contamination. DETAILED DESCRIPTION

[0010] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0011] Overall embodiment A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of ≤5 mm using a shear crusher, and magnetically separating the ribbon to remove iron impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 10% to 15% in a mass ratio of 1:2 to 3, stirring and reacting at 80° C. and 100 rpm for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7 to 8 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.1 to 0.5 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.8-1.2 g of dodecylamine, 0.4-0.6 g of terpineol, and 8-12 g of water added to every 100 g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 150-200 r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing it in a zone melting furnace with the temperature controlled at 960° C. to 1000° C., the melting zone length at 10 to 15 mm, and the moving speed at 12 mm / min for zone melting purification to obtain high-purity silver bars; Step (f) melting a high-purity silver bar at a melting temperature of 1050° C. to 1100° C., introducing argon gas as a protective gas during the melting process, adding a borax solution with a mass concentration of 0.1% to 0.2% in an amount of 0.5-0.8 mL per 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0012] Example 1 A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a 10% sodium hydroxide solution in a mass ratio of 1:2, stirring and reacting at 80° C. and 100 rpm for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7.5 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.3 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.8g of dodecylamine, 0.4g of terpineol, and 8g of water added to every 100g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 150r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing the concentrate in a zone melting furnace at a controlled temperature of 960° C., a melting zone length of 10 mm, and a moving speed of 12 mm / min for zone melting purification to obtain a high-purity silver bar; Step (f) melting the high-purity silver bar at a melting temperature of 1050° C., introducing argon gas as a protective gas during the melting process, adding a 0.1% borax solution in an amount of 0.5 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0013] Example 2 A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) mechanically crushing the photovoltaic ribbon to a particle size of 2.5 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 12% in a mass ratio of 1:2.5, stirring and reacting at 80° C. and 120 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7.5 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.2 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 1.0 g of dodecylamine, 0.5 g of terpineol, and 10 g of water added to every 100 g of the pretreated desiliconized material, and mechanically stirring the material in a flotation tank at a speed of 180 r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing it in a zone melting furnace at a controlled temperature of 980° C., a melting zone length of 12 mm, and a moving speed of 12 mm / min for zone melting purification to obtain high-purity silver bars; Step (f) melting the high-purity silver bar at a melting temperature of 1080° C., introducing argon gas as a protective gas during the melting process, adding a 0.15% borax solution in an amount of 0.6 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0014] Example 3 A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 3 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 15% in a mass ratio of 1:3, stirring and reacting at 80° C. and 150 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7.5 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.3 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 1.2 g of dodecylamine, 0.6 g of terpineol, and 12 g of water added to every 100 g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 200 r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing it in a zone melting furnace at a controlled temperature of 1000° C., a melting zone length of 15 mm, and a moving speed of 12 mm / min for zone melting purification to obtain high-purity silver bars; Step (f) melting a high-purity silver bar at a melting temperature of 1100° C., introducing argon gas as a protective gas during the melting process, adding a 0.2% borax solution in an amount of 0.8 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0015] Example 4 A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 11% in a mass ratio of 1:2.2, stirring and reacting at 80° C. and 110 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7.5 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.4 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.9g of dodecylamine, 0.45g of terpineol, and 9g of water added to every 100g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 160r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing the concentrate in a zone melting furnace at a controlled temperature of 970° C., a melting zone length of 11 mm, and a moving speed of 12 mm / min for zone melting purification to obtain a high-purity silver bar; Step (f) melting the high-purity silver bar at a melting temperature of 1060° C., introducing argon gas as a protective gas during the melting process, adding a 0.18% borax solution in an amount of 0.55 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0016] Comparative Example 1 The difference from Example 1 is that flotation method is not selected: A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 10% in a mass ratio of 1:2, stirring and reacting at 80° C. and 100 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7-8 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.3 mm to obtain a pretreated desiliconized material; Step (d) drying the pretreated desiliconized material in a vacuum drying oven at 120° C. for 2 h, and then placing it in a zone melting furnace at a controlled temperature of 960° C., a melting zone length of 10 mm, and a moving speed of 12 mm / min for zone melting purification to obtain a high-purity silver bar; Step (e) melting the high-purity silver bar at a melting temperature of 1050° C., introducing argon gas as a protective gas during the melting process, adding a 0.1% borax solution in an amount of 0.5 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0017] Comparative Example 2 The difference from Example 1 is that the zone melting process is not performed: A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 10% in a mass ratio of 1:2, stirring and reacting at 80° C. and 100 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7-8 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.3 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.8g of dodecylamine, 0.4g of terpineol, and 8g of water added to every 100g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 150r / min to ensure full contact between the flotation agent and the material; Step (e) melting the silver-enriched concentrate at a melting temperature of 1050° C., introducing argon gas as a protective gas during the melting process, adding a 0.1% borax solution in an amount of 0.5 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0018] Comparative Example 3 The difference from Example 1 is that it is not treated with sodium hydroxide: A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) grinding the crushed material to a particle size of 0.3 mm to obtain a pretreated desiliconized material; Step (c) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.8g of dodecylamine, 0.4g of terpineol, and 8g of water added to every 100g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 150r / min to ensure full contact between the flotation agent and the material; Step (d) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 h, and then placing it in a zone melting furnace at a controlled temperature of 960° C., a melting zone length of 10 mm, and a moving speed of 12 mm / min for zone melting purification to obtain high-purity silver bars; Step (e) melting the high-purity silver bar at a melting temperature of 1050° C., introducing argon gas as a protective gas during the melting process, adding a 0.1% borax solution in an amount of 0.5 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0019] Comparative Example 4 The difference from Example 1 is that the particle size of the desiliconized material is coarser by 0.8 mm: A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 10% in a mass ratio of 1:2, stirring and reacting at 80° C. and 100 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7-8 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.8 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.8g of dodecylamine, 0.4g of terpineol, and 8g of water added to every 100g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 150r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing the concentrate in a zone melting furnace at a controlled temperature of 960° C., a melting zone length of 10 mm, and a moving speed of 12 mm / min for zone melting purification to obtain a high-purity silver bar; Step (f) melting the high-purity silver bar at a melting temperature of 1050° C., introducing argon gas as a protective gas during the melting process, adding a 0.1% borax solution in an amount of 0.5 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0020] Comparative Example 5 The difference from Example 1 is that the particle size in step (c) is controlled to 0.08 mm: A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 10% in a mass ratio of 1:2, stirring and reacting at 80° C. and 100 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7-8 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.08 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.8g of dodecylamine, 0.4g of terpineol, and 8g of water added to every 100g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 150r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing the concentrate in a zone melting furnace at a controlled temperature of 960° C., a melting zone length of 10 mm, and a moving speed of 12 mm / min for zone melting purification to obtain a high-purity silver bar; Step (f) melting the high-purity silver bar at a melting temperature of 1050° C., introducing argon gas as a protective gas during the melting process, adding a 0.1% borax solution in an amount of 0.5 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0021] Comparative Example 6 The difference from Example 1 is that the flotation agent is different: A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 10% in a mass ratio of 1:2, stirring and reacting at 80° C. and 100 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7-8 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.3 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.8 g of sodium lauryl sulfate, 0.4 g of terpineol, and 8 g of water added to every 100 g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 150 r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing the concentrate in a zone melting furnace at a controlled temperature of 960° C., a melting zone length of 10 mm, and a moving speed of 12 mm / min for zone melting purification to obtain a high-purity silver bar; Step (f) melting the high-purity silver bar at a melting temperature of 1050° C., introducing argon gas as a protective gas during the melting process, adding a 0.1% borax solution in an amount of 0.5 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0022] Comparative Example 7 The difference from Example 1 is that the proportion of flotation agents is different: A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 10% in a mass ratio of 1:2, stirring and reacting at 80° C. and 100 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7-8 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.1 to 0.5 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 1.5 g of dodecylamine, 0.1 g of terpineol, and 8 g of water added to every 100 g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 150 r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing the concentrate in a zone melting furnace at a controlled temperature of 960° C., a melting zone length of 10 mm, and a moving speed of 12 mm / min for zone melting purification to obtain a high-purity silver bar; Step (f) melting the high-purity silver bar at a melting temperature of 1050° C., introducing argon gas as a protective gas during the melting process, adding a 0.1% borax solution in an amount of 0.5 mL / 100 g of silver liquid, and injecting the molten silver liquid into a mold preheated to 200° C. before casting, and obtaining a finished silver ingot after cooling.

[0023] Comparative Example 8 The difference from Example 1 is that no boric acid solution is added in step (f): A method for preparing silver ingots from photovoltaic ribbons comprises the following steps: Step (a) Mechanically crushing the photovoltaic ribbon to a particle size of 2 mm using a shear crusher, and magnetically separating the ferrous impurities using a strong magnetic field separator with a magnetic field strength of 1.2 T to obtain crushed material; Step (b) mixing the crushed material with a sodium hydroxide solution having a mass concentration of 10% in a mass ratio of 1:2, stirring and reacting at 80° C. and 100 r / min for 2 hours, performing solid-liquid separation by a plate and frame filter press, and washing the filter cake with deionized water until the pH value is 7-8 to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.3 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; the flotation agent comprises dodecylamine (industrial grade purity ≥98%), terpineol (food grade), and water in a mass ratio of 1:0.5:10, with 0.8g of dodecylamine, 0.4g of terpineol, and 8g of water added to every 100g of the pretreated desiliconized material; and mechanically stirring the material in a flotation tank at a speed of 150r / min to ensure full contact between the flotation agent and the material; Step (e) drying the silver-enriched concentrate in a vacuum drying oven at 120° C. for 2 hours, and then placing the concentrate in a zone melting furnace at a controlled temperature of 960° C., a melting zone length of 10 mm, and a moving speed of 12 mm / min for zone melting purification to obtain a high-purity silver bar; Step (f) melting the high-purity silver bar at a melting temperature of 1050°C, introducing argon gas for protection during the melting process, and injecting the molten silver liquid into a mold preheated to 200°C before casting, and obtaining a finished silver ingot after cooling.

[0024] The purity was tested and the recovery rate (the ratio of the actual recovery value to the theoretical recovery value) was calculated. The results are shown in Table 1.

[0025] Table 1 Purity and recovery results of Examples and Comparative Examples

[0026] The core reason why Examples 1-4 achieve better results than the comparative examples is that they systematically solve the key bottleneck of separation-enrichment-purification in the silver recovery process through multi-step coordinated optimization, while the comparative examples have significantly reduced efficiency due to the lack or destruction of a core link. Specifically: Example 1 achieved efficient separation and purification of silver by crushing to control the particle size ≤ 5mm; alkaline leaching for desiliconization; flotation, using dodecylamine to adsorb silver particles to make them hydrophobic, and pineol to stabilize the foam to enrich silver; zone melting, using the difference in impurity segregation coefficient to remove residual metals; borax refining, a complete process to assist in removing trace impurities. In Comparative Example 1, since flotation was not used, silver was uniformly mixed with impurities such as copper and silicon, and zone melting could not specifically separate metal impurities, resulting in a significant reduction in silver recovery rate; in Comparative Example 2, since the zone melting step was missing, impurities such as copper and zinc still remained in the silver concentrate after flotation, and the purity could not be further improved; in Comparative Example 3, since alkaline leaching for desiliconization was skipped, silicon-based impurities were not dissolved, and agglomerated with silver particles to form a hydrophobic barrier, hindering the adsorption of silver by dodecylamine, and the flotation efficiency was significantly reduced; in Comparative Example 4, since the desiliconized material was ground too coarsely, the surface of the silver particles was difficult to be effectively hydrophobically modified by dodecylamine, the bubble attachment efficiency was reduced, and the flotation recovery rate was greatly reduced; in Comparative Example 5, since the desiliconized material was ground too finely, the silver particles were not effectively hydrophobicized by dodecylamine, the bubble attachment efficiency was reduced, and the flotation recovery rate was significantly reduced. , fine particles are easy to agglomerate and wrap impurities such as silicon micropowder, and impurities float up with bubbles during flotation, resulting in silver loss; Comparative Example 6 uses the wrong anion collector, sodium dodecyl sulfate instead of dodecylamine, which has weaker ability to weaken the hydrophilicity of the silver surface than dodecylamine, the foam layer is thin and unstable, and the silver recovery rate is significantly reduced; Comparative Example 7 has an unbalanced flotation agent ratio, excessive foam volume but reduced selectivity, and copper impurities are entrained. At the same time, the foam stability is poor, silver particles are easy to fall off, and both the recovery rate and purity are reduced; Comparative Example 8 does not add borax, which cannot assist in removing residual trace impurities such as calcium and magnesium during melting, and the silver purity is slightly lower than that of Example 1.

[0027] In summary, the comparative example lacks or incorrectly executes a key step, resulting in reduced efficiency in silver enrichment, separation or purification, which ultimately results in a double decrease in purity and recovery rate.

Claims

1. A method for preparing silver ingots from photovoltaic ribbons, characterized in that: The following steps are involved: Step (a) mechanically crushing the photovoltaic ribbon to obtain crushed material; Step (b) desiliconizing the crushed material to obtain a desiliconized material; Step (c) grinding the desiliconized material to a particle size of 0.1 to 0.5 mm to obtain a pretreated desiliconized material; Step (d) adding a flotation agent to the pretreated desiliconized material for flotation separation to obtain a silver-enriched concentrate; The flotation agent includes dodecylamine, terpineol and water, and 0.8-1.2g of dodecylamine, 0.4-0.6g of terpineol and 8-12g of water are added to every 100g of pretreated desiliconized material; Step (e) drying the silver-enriched concentrate, zone melting and purification to obtain high-purity silver bars; Step (f) melts the high-purity silver bars, casts them, and cools them to obtain finished silver ingots.

2. The method for preparing silver ingots from photovoltaic ribbons according to claim 1, wherein: In step (a), the particle size of the crushed material is ≤5 mm.

3. The method for preparing silver ingots from photovoltaic ribbons according to claim 1, wherein: In step (a), the photovoltaic ribbon is mechanically crushed and magnetically separated to remove impurities in a 1.2T magnetic field to obtain crushed material.

4. The method for preparing silver ingots from photovoltaic ribbons according to claim 1, wherein: In step (b), the process of desiliconization of the crushed material is as follows: mixing the crushed material with an alkali solution, reacting the mixture, separating the mixture, and washing the mixture to obtain a desiliconized material.

5. The method for preparing silver ingots from photovoltaic ribbons according to claim 4, wherein: The process of mixing the crushed material with the alkali solution is as follows: mixing the crushed material with a sodium hydroxide solution with a mass concentration of 10%-15% in a mass ratio of 1:2-3, stirring and reacting at 80°C and 100 r / min for 2 hours, performing solid-liquid separation through a plate and frame filter press, and washing the filter cake with deionized water to a pH value of 7-8 to obtain a desiliconized material.

6. The method for preparing silver ingots from photovoltaic ribbons according to claim 1, wherein: In step (d), during the flotation separation process, the stirring speed is 150-200 r / min.

7. The method for preparing silver ingots from photovoltaic ribbons according to claim 1, wherein: In step (e), the zone melting purification process is as follows: the silver-enriched concentrate is dried and placed in a zone melting furnace, and the zone melting purification is carried out by controlling the temperature to 960°C to 1000°C, the melting zone length to 10-15 mm, and the moving speed to 12 mm / min.

8. The method for preparing silver ingots from photovoltaic ribbons according to claim 7, wherein: The process for drying the silver-enriched concentrate is: drying in a vacuum drying oven at 120° C. for 2 hours.

9. The method for preparing silver ingots from photovoltaic ribbons according to claim 1, wherein: In step (f), the melt casting and cooling process is as follows: melting at 1050°C to 1100°C under argon conditions, injecting the molten silver liquid into a mold preheated to 200°C before casting, and obtaining a finished silver ingot after cooling.

10. The method for preparing silver ingots from photovoltaic ribbons according to claim 9, wherein: In step (f), the melt casting and cooling process is as follows: melting at 1050°C to 1100°C under argon conditions, adding a borax solution with a mass concentration of 0.1% to 0.2% in an amount of 0.5-0.8 mL / 100 g of silver liquid, injecting the molten silver liquid into a mold preheated to 200°C before casting, and obtaining a finished silver ingot after cooling.

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