A short-process green technology for synergistically recovering indium, bismuth, gallium and tellurium from multi-metal mixed waste materials

Abstract

The present application belongs to the field of scattered metal wet recovery technology, and provides a short-process green process for synergistic recovery of indium, bismuth, gallium and tellurium from multi-metal mixed waste. Traditional process recovers four metals by separate lines, which has long process, high equipment investment, high energy consumption, uses strong acid containing chlorine and organic extraction reagent, and has serious three-waste pollution, and the comprehensive recovery rate of metals is less than 80%, and most of the improved processes can only co-produce two metals. The present application adopts a closed crushing and screening, chlorine-free composite leaching, stepwise selective separation, metal purification and waste liquid closed loop recycling integrated single production line process, which does not need material diversion, has no chlorine and organic extraction pollution in the whole process, and the waste liquid is recycled and reused. The present process can simultaneously produce 4N high-purity indium, bismuth, gallium and tellurium, and the comprehensive recovery rate of the four metals is all greater than or equal to 88%, the equipment investment, site and energy consumption are greatly reduced, and the present process is suitable for various metallurgical slag and photovoltaic electronic waste containing four kinds of scattered metals, and has outstanding industrialization economy and environmental protection advantages.

Description

Technical Field

[0001] This invention relates to the field of synergistic resource recovery and green co-production hydrometallurgical technology for multiple rare and dispersed metals. Specifically, it is applicable to an integrated, short-process, green co-production purification process for mixed smelting anode mud, composite rare and dispersed metal metallurgical slag, and waste photovoltaic and electronic mixed waste. It is mainly used to simultaneously recover and purify four strategic rare and dispersed metals, indium, bismuth, gallium, and tellurium, from the waste.

[0002] (1) The existing mainstream recycling processes are all single metal independent recycling modes. For mixed waste containing four metals, multiple pre-treatment processes such as crushing and screening, grading and sorting, and material diversion need to be added in the early stage. The mixed materials are split and sent to different production lines and different equipment to recycle the corresponding metals. The process flow is long and the overall production cycle is increased by more than 40%. (2) Under the parallel production mode of multiple production lines, enterprises need to be equipped with multiple sets of special equipment for leaching, separation and purification. The fixed asset investment cost is high and the land area is large. At the same time, the simultaneous operation of multiple production lines will greatly increase the water and electricity consumption and labor costs, resulting in high production and operation pressure. (3) Traditional recycling processes often use chlorine-containing strong acid leaching systems, organic extractants, and high-temperature open flame smelting processes. During the production process, pollutants such as chlorine gas, sulfur dioxide toxic fumes, high-salt chlorine-containing wastewater, and waste organic extract liquid are easily generated. The cost of treating the three wastes is high, and environmental compliance is difficult. (4) The traditional diversion and recycling mode has a large amount of material loss and serious metal entrainment and loss in each process. The comprehensive recovery rate of indium, cylindrica, gallium and tellurium can only reach 75%, 80%, 72% and 70% respectively, resulting in low resource utilization efficiency. (5) Some modified wet processes can only achieve the co-production of two metals and cannot be adapted to the simultaneous separation and purification of four metals. They have narrow adaptability and cannot meet the industry demand for large-scale integrated treatment of composite waste.

[0003] In summary, developing an integrated recycling process that is short-process, low-investment, green and pollution-free, and has high resource utilization, capable of simultaneously producing indium, bismuth, gallium, and tellurium on a single production line, is a technical challenge that urgently needs to be solved in the field of rare and dispersed metal recycling. 5. Summary of the Invention 5.1 Purpose of the Invention

[0004] To address the shortcomings of existing single-metal recycling processes, such as lengthy processes, high equipment investment, high energy consumption, severe environmental pollution, low resource utilization, and the inability to achieve the synergistic co-production of four metals (indium, bismuth, gallium, and tellurium), this invention provides a short-process green process for the synergistic recovery of indium, bismuth, gallium, and tellurium from multi-metal mixed waste. This process enables the simultaneous co-production of four high-purity rare and dispersed metals on a single modular production line, simplifies production procedures, reduces equipment investment and energy consumption, eliminates toxic pollutant emissions, improves the overall metal recovery rate, and solves many pain points of existing technologies. 5.2 Technical Solution

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a short-process green process for the synergistic recovery of indium, bismuth, gallium, and tellurium from multi-metal mixed waste, comprising the following steps: S1. Raw material pretreatment: Collect multi-metal mixed waste (mixed anode mud, composite metallurgical slag, and waste photovoltaic electronics), send the waste into a closed crusher for crushing, pass it through an 80-150 mesh standard sieve, remove inert impurities such as plastics, resins, and sand and gravel after sieving, and obtain homogeneous powdered material to be processed; send the powdered material into a constant temperature drying oven and dry it at 60-80℃ for 2-4 hours to remove free moisture from the surface of the material, and set it aside for later use; S2, One-step green co-leaching: The pretreated material and the independently developed chlorine-free ternary composite green leaching agent are added to a closed atmospheric pressure leaching reactor at a solid-liquid ratio of 1:4~1:8 (g / mL), and the mixture is stirred at a uniform speed to adjust the slurry. The reaction temperature is controlled at 45~75℃, the stirring speed at 300~500r / min, and the reaction time at 3~6h. After the reaction, the mixture is filtered to separate a mixed leaching solution rich in indium, bismuth, gallium, and tellurium and an inert leaching residue. The inert leaching residue is collected and disposed of in a harmless manner. The chlorine-free ternary composite green leaching agent is composed of inorganic weak acid, complexing agent, and oxidizing agent, and does not contain chloride ions or strong acid corrosive media throughout the process. S3, Stepwise Selective Separation: S301, Selective bismuth precipitation: A quantitative organic sulfide agent is added dropwise to the mixed leachate at a uniform rate, the pH of the solution is adjusted to 2.5~4.0, and the reaction is stirred at a constant temperature of 35~50℃ for 1~2 hours. After the reaction is completed, the mixture is precisely filtered to obtain bismuth sulfide precipitate and bismuth removal mother liquor. The bismuth sulfide precipitate is washed with deionized water 2~3 times for later use. S302, Low-temperature reduction precipitation of tellurium: Add reducing grade iron powder in batches to the above bismuth removal mother liquor. The amount of iron powder added is 1.1 to 1.3 times the theoretical reaction amount of tellurium ions in the mother liquor. Control the reaction temperature at 25 to 40°C and the pH value at 1.5 to 3.0. Stir the reduction reaction at low speed for 1.5 to 3 hours. Filter and separate to obtain elemental tellurium crude material and bismuth-tellurium separation mother liquor. S303, Stepwise Adsorption Separation of Gallium and Indium: Two special chelating adsorption resins are used to perform stepwise adsorption treatment on the bismuth-tellurium separation mother liquor. First, gallium-specific adsorption resin is used to capture gallium ions in the solution, and after elution with the eluent, gallium-rich eluent is obtained. Then, the indium-specific adsorption resin is replaced to adsorb indium ions in the remaining mother liquor, and after elution, indium-rich eluent is obtained. Finally, gallium and indium are completely separated without metal cross-contamination. The tail liquid after adsorption is recycled to the leaching process. S4. Refined metal purification: S401, Bismuth purification: Bismuth sulfide precipitate is placed in a low-temperature alkaline dissolution reactor and dissolved using a weak alkaline system. After filtration to remove impurities, a bismuth electrolyte is prepared. Cathode bismuth is prepared using a low-temperature constant current electrodeposition process. Finally, it is deeply purified in a vacuum refining furnace at 280~350℃ to obtain 4N high-purity metallic bismuth. S402, Tellurium purification: After the crude elemental tellurium is acid-washed to remove impurities, washed with deionized water, and dried, it is sent to a vacuum refining furnace for distillation purification under negative pressure at 320~380℃ to obtain 4N high-purity metallic tellurium. S403, Gallium Purification: After pH fine-tuning and chelation removal of trace impurities, the gallium-rich solution is used to prepare a special gallium electrolyte. Low-temperature pulse electrowinning technology is used to prepare crude gallium cathode. The crude gallium is purified by zone melting process to obtain 4N high-purity metallic gallium. S404, Indium Purification: The indium-rich electrolyte undergoes deep purification treatments to remove copper, lead, and tin in sequence. The purified electrolyte is then subjected to low-temperature electrodeposition to prepare crude indium cathode. Combined with vacuum annealing refining process, 4N high-purity metallic indium is obtained. S5. Closed-loop circulation throughout the entire process: All washing wastewater, analytical waste liquid, and waste electrolyte generated in this process are collected in a waste liquid mixing tank. After fine-tuning of the composition and replenishment of additives, they are returned to the corresponding processes such as leaching, adsorption, and washing for recycling. Only a small amount of waste liquid is periodically treated to render it harmless, thus achieving a closed-loop circulation of water resources and chemical additives. 5.3 Preferred Solution

[0006] Furthermore, the chlorine-free ternary composite green leaching agent described in S2, by mass percentage, comprises 15%~25% inorganic weak acid, 8%~15% complexing agent, 3%~8% oxidizing agent, and the balance being deionized water; the inorganic weak acid is any one or more of citric acid, oxalic acid, and tartaric acid in combination; the complexing agent is one of aminotriacetic acid and disodium EDTA; and the oxidizing agent is one of hydrogen peroxide and sodium percarbonate.

[0007] Furthermore, the organic vulcanizing agent mentioned in S301 is sodium dimethyl dithiocarbamate, and the amount added is 2% to 5% of the volume of the mixed leachate.

[0008] Furthermore, the gallium-specific adsorption resin in S303 is an aminophosphonic acid chelating resin, and the indium-specific adsorption resin is an imine diacetic acid chelating resin; the eluent is a low-concentration weak base buffer solution.

[0009] Furthermore, the low-temperature electrowinning process described in S4 controls the temperature to be 20~55℃ and the current density to be 15~40A / ㎡, with no high-temperature heating throughout the process. 5.4 Beneficial Effects

[0010] Compared with existing traditional rare metal recycling technologies, this invention has the following key advantages: (1) Short process flow and low investment cost: The first integrated short process of one-step co-immersion + step-by-step separation eliminates redundant pre-treatment processes such as material diversion, multi-stage screening and multi-production line splitting in traditional processes. A single modular production line can simultaneously produce four metals. The equipment investment is reduced by more than 50% compared with the traditional multi-production line process, the site area is reduced by 60%, and the overall operating energy consumption is reduced by 35%~45%. (2) Green and environmentally friendly with extremely low emissions of waste: The entire process adopts a chlorine-free leaching system, abandoning chlorine-containing strong acids, toxic organic extractants, and open flame high-temperature smelting processes. No chlorine or sulfur dioxide toxic fumes are generated during the production process. Relying on the closed-loop recycling system of waste liquid throughout the entire line, the wastewater discharge rate is less than 5%, there are no waste organic extract pollutants, the amount of solid waste output is greatly reduced, and the cost of environmental protection is significantly reduced. (3) High resource utilization and stable product quality: The step-by-step separation parameters are designed to match the physical and chemical properties of the four metals, effectively avoiding the problem of cross-contamination between metals. The comprehensive recovery rates of indium, bismuth, gallium and tellurium can reach 92%, 95%, 90% and 88% respectively, which are far higher than traditional processes. After purification, the purity of the four metals can be stably reached 4N (99.99%), which meets the standards for use in high-end fields such as semiconductors and photovoltaics. (4) Wide adaptability and strong industrialization: This process can be adapted to multi-metal mixed waste of different types and different metal contents, and has strong raw material compatibility; the whole process operates at normal pressure and low temperature, the equipment is simple to operate and has a high degree of automation, and the production capacity can be flexibly adjusted according to production needs, which is suitable for the large-scale implementation of small and medium-sized recycling enterprises and large smelting enterprises. (5) Significant economic benefits: A single production line can simultaneously produce four high-value-added strategic rare metals, avoid the risk of price fluctuations of a single metal, increase the comprehensive added value of waste materials, and greatly improve the company's production profit margin. 6. Description of the attached drawings

[0011] Appendix Figure 1 Overall process flow diagram of multi-metal co-production Process flow: Raw material pretreatment → one-step co-leaching with chlorine-free ternary composite leaching agent → pressure filtration (inert slag harmless treatment) → mixed leaching solution → selective sulfidation precipitation of bismuth → low-temperature iron powder reduction precipitation of tellurium → stepwise adsorption and separation of gallium and indium by resin → low-temperature electrowinning of the four major metal crude materials + vacuum / zone melting refining → production of 4N high-purity indium, bismuth, gallium, and tellurium; all waste liquids are uniformly recycled and mixed, and recycled back to each process in a closed loop for reuse. 7. Specific Implementation Examples 7.1 Example 1

[0012] In this embodiment, the raw material used is copper smelting multi-metal mixed anode slime. The main metal contents of the anode slime are: In 2.15%, Bi 5.32%, Ga 1.08%, and Te 1.86%. The specific process steps are as follows: (1) Pretreatment: Take 10 kg of mixed anode mud, crush it and pass it through a 100-mesh sieve, dry it at 70℃ for 3 hours to remove moisture and inert impurities, and obtain 9.82 kg of homogeneous material; (2) One-step co-leaching: The slurry was prepared with a solid-liquid ratio of 1:6, and a chlorine-free ternary composite leaching agent (20% citric acid, 12% disodium EDTA, 5% hydrogen peroxide, and 63% deionized water) was used. The reaction temperature was 60℃, the stirring speed was 400r / min, and the leaching time was 4h. After pressure filtration, the leaching rates of the four metals were: In 93.6%, Bi 96.1%, Ga 91.5%, and Te 89.7%. (3) Stepwise separation: 3% sodium dimethyl dithiocarbamate (by volume) was added to the mixed leachate, and the reaction was carried out at pH 3.2 and 42°C for 1.5 h. The bismuth sulfide was obtained by filtration. 1.2 times the theoretical amount of reducing iron powder was added to the bismuth removal mother liquor, and the reduction was carried out at 30°C and pH 2.2 for 2 h to obtain elemental tellurium crude material. Subsequently, gallium and indium were separated by adsorption using aminophosphonic acid type resin and imine diacetic acid type resin in sequence. (4) Refining: The four types of metal crude materials were subjected to low-temperature electrodeposition and vacuum refining, with an electrodeposition temperature of 40℃ and a current density of 25A / ㎡; finally, 4N high-purity bismuth, tellurium, gallium and indium were obtained, with comprehensive recovery rates of 95.2%, 88.6%, 90.3% and 92.1%, respectively. (5) Waste liquid recycling: The waste liquid of the process is uniformly mixed and then returned to the leaching unit, with a waste liquid recycling rate of 96%. 7.2 Example 2

[0013] In this embodiment, the raw material selected is a mixed waste of discarded photovoltaic electronics, with the following main metal contents: In 1.68%, Bi 3.25%, Ga 2.36%, Te 1.52%. The specific process steps are as follows: (1) Pretreatment: Take 10kg of photovoltaic electronic waste, crush it and pass it through a 120-mesh sieve, dry it at 65℃ for 2.5h to remove plastic and resin impurities, and obtain 9.56kg of homogeneous material; (2) One-step co-leaching: The slurry was prepared with a solid-liquid ratio of 1:5, and a chlorine-free ternary composite leaching agent (18% oxalic acid, 10% aminotriacetic acid, 6% sodium percarbonate, and 66% deionized water) was used. The reaction temperature was 55℃, the stirring speed was 450r / min, and the leaching time was 5h. The leaching rates of the four metals were: In 92.8%, Bi 95.5%, Ga 90.8%, and Te 88.9%. (3) Stepwise separation: Add 2.5% by volume organic sulfide agent, precipitate bismuth at pH=3.5 and 38℃; add 1.15 times the theoretical amount of iron powder, reduce and precipitate tellurium at 35℃; separate gallium and indium by stepwise adsorption of resin; (4) Refined purification: High-purity metals were prepared by vacuum refining at an electrodeposition temperature of 35℃ and a current density of 30A / m²; the comprehensive recovery rates of the four metals were 91.8%, 94.7%, 90.1%, and 87.9%, respectively. (5) Waste liquid recycling: The waste liquid recycling rate of the entire line is 95.5%. 7.3 Comparative Example (Traditional Single-Diversion Recycling Process)

[0014] The traditional process of leaching with chlorine-containing strong acid, organic extraction, and high-temperature smelting is adopted. The raw materials used in the comparative example are the same copper smelting anode mud as those in Example 1. The process involves material diversion and independent recycling in four production lines. The equipment investment is 2.1 times that of the present invention, and the overall energy consumption is 42% higher. The comprehensive recovery rates of indium, bismuth, gallium, and tellurium are only 74.2%, 79.5%, 71.6%, and 69.8%, respectively. The production process generates high-salt chlorine-containing wastewater, waste extractant, and sulfur dioxide flue gas. The cost of treating these three wastes is 2.8 times that of the present invention, which fully demonstrates the technical advantages of the present invention.

Claims

1. A short-process green process for the synergistic recovery of indium, bismuth, gallium, and tellurium from polymetallic mixed waste, characterized in that, Includes the following steps: S1. Raw material pretreatment: The multi-metal mixed waste is crushed, passed through an 80-150 mesh sieve to remove inert impurities, and then dried at 60-80℃ for 2-4 hours to obtain a homogeneous powdered material to be processed; the multi-metal mixed waste is any one or more of the following: mixed smelting anode mud containing indium, bismuth, gallium and tellurium, composite rare and dispersed metal metallurgical slag, and waste photovoltaic electronic mixed waste; S2, One-step green co-leaching: The pretreated material and the chlorine-free ternary composite green leaching agent are put into a closed leaching reactor at a solid-liquid ratio of 1:4~1:8 (g / mL). The mixture is leached at a constant temperature of 45~75℃ and 300~500r / min for 3~6h. After pressure filtration, a mixed leaching solution and an inert leaching residue are obtained. S3, Stepwise Selective Separation: S301, Selective bismuth precipitation: Add an organic sulfide agent dropwise to the mixed leachate, adjust the pH value to 2.5~4.0, react at 35~50℃ for 1~2h, and filter to obtain bismuth sulfide precipitate and bismuth removal mother liquor; S302, Low-temperature reduction precipitation of tellurium: Add reducing grade iron powder to the bismuth removal mother liquor. The amount of iron powder added is 1.1 to 1.3 times the theoretical reaction amount of tellurium ions in the mother liquor. The reduction reaction is carried out at 25 to 40°C and pH 1.5 to 3.0 for 1.5 to 3 hours. The mixture is then filtered to obtain elemental tellurium coarse material and bismuth-tellurium separation mother liquor. S303, Stepwise adsorption separation of gallium and indium: Gallium-specific adsorption resin and indium-specific adsorption resin are used to sequentially adsorb and desorb the bismuth-tellurium separation mother liquor to obtain gallium-rich desorbent and indium-rich desorbent, respectively. The adsorption tail liquid is recycled to the S2 leaching process. S4. Refined purification of metals: Low-temperature electrowinning combined with vacuum refining / zone melting is used to purify bismuth sulfide precipitate, elemental tellurium crude material, gallium-rich leaching solution, and indium-rich leaching solution to prepare 4N high-purity bismuth, tellurium, gallium, and indium metals respectively. S5. Closed-loop circulation throughout the entire process: The washing wastewater, analytical waste liquid, and waste electrolyte generated in all processes are collected, and after being mixed and supplemented with additives, they are returned to the corresponding production processes for recycling.

2. The short-process green process for the co-recovery of indium, bismuth, gallium, and tellurium from polymetallic mixed waste according to claim 1, characterized in that: The chlorine-free ternary composite green leaching agent described in S2, by mass percentage, comprises 15%~25% inorganic weak acid, 8%~15% complexing agent, 3%~8% oxidizing agent, and the balance being deionized water; the leaching agent is completely free of chloride ions and highly corrosive hydrochloric acid and nitric acid media throughout the entire process.

3. The short-process green process for the synergistic recovery of indium, bismuth, gallium, and tellurium from polymetallic mixed waste according to claim 2, characterized in that: The inorganic weak acid is any one or more of citric acid, oxalic acid, and tartaric acid in combination; the complexing agent is one of aminotriacetic acid and disodium EDTA; and the oxidizing agent is one of hydrogen peroxide and sodium percarbonate.

4. The short-process green process for the co-recovery of indium, bismuth, gallium, and tellurium from polymetallic mixed waste according to claim 1, characterized in that: The organic vulcanizing agent described in S301 is sodium dimethyl dithiocarbamate, and the volume of the organic vulcanizing agent added is 2% to 5% of the total volume of the mixed leachate.

5. The short-process green process for the co-recovery of indium, bismuth, gallium, and tellurium from polymetallic mixed waste according to claim 1, characterized in that: The gallium-specific adsorption resin in S303 is an aminophosphonic acid chelating resin, and the indium-specific adsorption resin is an imine diacetic acid chelating resin; the elution solution used for adsorption and desorption is a low-concentration weak base buffer solution.

6. The short-process green process for the co-recovery of indium, bismuth, gallium, and tellurium from polymetallic mixed waste according to claim 1, characterized in that: The low-temperature electrowinning process described in S4 operates at a temperature of 20~55℃, with a current density controlled at 15~40A / ㎡, and involves no open flame high-temperature smelting process throughout.

7. The short-process green process for the co-recovery of indium, bismuth, gallium, and tellurium from polymetallic mixed waste according to claim 1, characterized in that: The vacuum refining temperature for bismuth purification in S4 is 280~350℃, and the vacuum refining temperature for tellurium purification is 320~380℃.

8. The short-process green process for the co-recovery of indium, bismuth, gallium, and tellurium from polymetallic mixed waste according to claim 1, characterized in that: All processes in this technology are completed under normal pressure. No organic extractants are involved in the reaction, and there is no emission of toxic sulfur dioxide fumes.

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