Method for recovering tellurium, tin and indium from zinc oxide waste

Abstract

The invention provides a method for recovering tellurium, tin and indium from zinc oxide waste, which belongs to the technical field of non-ferrous metallurgy and comprises the following steps: adding water into the zinc oxide waste, stirring and filtering to obtain pre-leached slag; adding calcium sulfate seed crystals into the leaching agent solution of the pre-leached residues, heating and stirring, and leaching with hydrogen peroxide to obtain a tellurium / tin / indium-containing leaching solution; carrying out electro-deposition on the leachate to recover tellurium powder and obtain an electrolyte; extracting and layering a mixed system of the electrolyte and the organic phase to obtain a tin-enriched organic phase and raffinate; the tin-enriched organic phase is washed and reversely extracted to obtain tin-containing strip liquor, and tin dioxide is prepared through hydrolytic precipitation and roasting; and oxidizing the raffinate, adjusting the pH value, aging, precipitating, drying and roasting to prepare indium oxide. According to the method, the problems of high acid corrosion and high chlorine salt enrichment can be avoided, the tellurium / tin / indium step-by-step separation and recovery are realized, and the method has a relatively good recovery rate.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal metallurgy, specifically to a method for recovering tellurium, tin, and indium from zinc oxide waste. Background Technology

[0002] Zinc oxide waste is a type of fine-particle solid byproduct with ZnO as the main phase, containing various volatile or volatile metal oxides / salts. Common forms include reduced and volatilized zinc oxide dust, secondary zinc oxide dust, and Waldze oxides. Due to the complex sources of raw materials and fluctuating operating conditions, in addition to Zn, the aforementioned zinc oxide waste often contains enriched indium, tin, and trace amounts of tellurium and other rare or associated metals, and may also contain impurities such as lead, cadmium, chloride salts, and fluoride salts. Indium, tin, and tellurium have high resource and application value, but their content in zinc oxide waste is relatively low and they exist in various forms. If they are directly disposed of as general solid waste or only zinc is recovered, it is easy to cause the loss of valuable metals and increase environmental risks.

[0003] For the recovery of multiple metals from zinc oxide waste, existing technologies generally focus on wet leaching, separation and enrichment, and productization. Firstly, acid leaching systems (such as sulfuric acid systems) are used to dissolve ZnO and allow some indium to enter the leaching solution. Alternatively, a combination of neutral leaching and staged high-acid leaching is used to achieve phased separation of zinc and indium. For indium present in the difficult-to-leach phase, methods such as temperature enhancement, acid aging, and ultrasonic or microwave-enhanced mass transfer are often used to improve the leaching rate. For tin and tellurium, some processes use chlorination systems to promote the formation of chloride complexes for leaching, or use alkaline leaching to convert tellurium oxide into soluble tellurate or tellurite before reduction precipitation and electrodeposition for recovery. For example, patent document CN104388685A discloses a method for recovering copper bismuth telluride from zinc oxide flue dust. This method achieves tellurium enrichment and recovery in zinc oxide flue dust through a process of one neutral leaching, one acidic leaching, two neutral leachings, two acidic leachings, and reduction. However, in the acidic leaching process, a high-concentration sulfuric acid solution and a chlorination system are directly used for impregnation. In a highly acidic environment, this can easily cause equipment corrosion, increase production costs, and affect equipment lifespan. Furthermore, the chlorination system can easily lead to the enrichment of chloride salts, which not only increases the difficulty of tailings treatment.

[0004] In addition, indium, tin, and tellurium in zinc oxide waste exist in various forms and are partially encapsulated or dissolved in the difficult-to-leach phase. Conventional acid leaching is difficult to balance leaching rate and selectivity, and complex salt deposition and co-precipitation may occur in lead-containing systems, affecting the recovery rate of target elements. Furthermore, tellurium often exists in trace amounts or multiple valence states and behaves similarly to elements such as sulfur and selenium. In existing processes, it is easy to be lost or have unstable distribution during the purification or precipitation stages, making it difficult to achieve the synergistic recovery of tellurium, tin, and indium.

[0005] Therefore, there is a need to provide a method for recovering tellurium, tin, and indium from zinc oxide waste to solve the problems existing in the prior art. Summary of the Invention

[0006] In view of this, the present invention provides a method for recovering tellurium, tin and indium from zinc oxide waste, which can avoid the problems of high acid corrosion and high chloride salt enrichment while achieving stepwise separation and recovery of tellurium / tin / indium, and has a good recovery rate.

[0007] To achieve the above objectives, the present invention provides a method for recovering tellurium, tin, and indium from zinc oxide waste, comprising the following steps: S1. Mix deionized water, tartaric acid, anhydrous sodium sulfate, and concentrated sulfuric acid to prepare an leaching agent solution; mix trioctylamine, tributyl phosphate, and sulfurized kerosene to obtain an organic phase mixture system. S2. Add zinc oxide waste to deionized water, stir, filter, and obtain pre-leaching residue; S3. Add the pre-leaching residue to the leaching agent solution and add calcium sulfate seed crystals, heat and stir, add hydrogen peroxide and continue stirring to leach, filter to obtain tellurium / tin / indium leaching solution and leaching residue; S4. The tellurium / tin / indium leaching solution is placed in an electrodeposition apparatus for electrodeposition, the cathode deposit is recovered, tellurium powder is obtained, and an electrolyte is obtained. S5. Mix the electrolyte and organic phase mixture system for extraction, allow it to stand and separate into layers, and separate the tin-enriched organic phase and raffinate; wash and back-extract the tin-enriched organic phase to obtain a tin-containing back-extract, hydrolyze it to obtain a tin-containing precipitate, and calcine it to obtain tin dioxide. S6. Add hydrogen peroxide solution to the raffinate, adjust the pH, age, dry, and calcine to obtain indium oxide.

[0008] This invention employs a composite leaching system for leaching Te / Sn / In, with sulfuric acid as the main component, tartaric acid as the coordination regulator, and anhydrous sodium sulfate to enhance the strength of the sulfate medium. Sulfuric acid provides stable acidity and a sulfate medium, dissolving the oxide / alkaline phase and promoting the migration of tellurium (Te), tin (Sn), and indium (In) into the leachate. Tartaric acid, through complexation, regulates the state of some metal ions in the solution, mitigating the local hydrolysis and redeposition tendency of easily hydrolyzed components such as tin during leaching, and also helps promote the release and migration of Te, Sn, and In in the difficult-to-leach or composite phases. Simultaneously, the addition of anhydrous sodium sulfate enhances the strength of the sulfate medium (sulfate ion activity and ionic strength), which is beneficial for the preferential stabilization of impurities such as lead in sulfate form, reducing the risk of fine-particle deposition, entrainment, and leachate turbidity, thereby improving the solid-liquid separation efficiency and process stability after leaching. Thus, without significantly increasing acidity and temperature, it achieves both target metal leaching efficiency and selectivity, while reducing acid consumption, impurity load, and corrosion risks caused by intensified conditions.

[0009] In step S3, calcium sulfate seed crystals are added to induce the orderly nucleation and growth of sulfate deposits (such as calcium sulfate, lead sulfate, etc.). This allows any sulfates that may precipitate in the system to preferentially form larger particles on the seed crystal surface, avoiding the formation of a large number of fine suspended crystals or colloidal deposits. This reduces the turbidity and entrainment loss of the leachate, improves the filtration rate, and can, to some extent, inhibit scaling and co-precipitation, thereby improving the operational stability and solid-liquid separation effect of the leaching section.

[0010] This invention utilizes a mixed extraction system of trioctylamine, tributyl phosphate, and sulfurized kerosene to achieve selective transfer of tin in acidic sulfate media. Trioctylamine, after protonation under acidic conditions, can form ion associations with extractable tin complexes, thereby improving tin loading capacity and separation selectivity. Tributyl phosphate acts as a synergistic and phase-regulating agent, improving the solubilization environment of the organic phase and suppressing emulsification and third-phase tendencies, resulting in more stable extraction and phase separation. Sulfurized kerosene, as a dilution and stabilizing medium, reduces system viscosity, enhances anti-entrainment capabilities, and improves the reliability of continuous operation under complex leaching conditions. This mixed system enables tin enrichment and reduces impurity co-extraction, facilitating subsequent productization.

[0011] This invention employs a sequential approach to recover tellurium (Te), followed by tin (Sn), and then indium (In). Tellurium is highly sensitive to valence state changes and pH fluctuations in acidic leaching solutions. If precipitation purification or solvent extraction is performed first, there is a risk of tellurium being entrained by impurities or lost during pH adjustments. Therefore, removing tellurium first via electrodeposition reduces the impact of subsequent process fluctuations on tellurium recovery. After tellurium removal, the solution maintains suitable acidic sulfate conditions with reduced interference, making selective extraction of tin more conducive to achieving stable phase separation and reducing the risk of co-extraction. Indium typically has low content and is easily affected by zinc load. Placing indium recovery after tin separation and enriching and precipitating it under reduced zinc load conditions reduces reagent consumption and the tendency for co-precipitation. Thus, this sequential arrangement allows each metal to be separated and fixed in its most suitable medium, forming a synergistic process that mutually yields and enhances each other, comprehensively improving the overall recovery rate of Te, Sn, and In while reducing impurity load and scaling risk.

[0012] Optionally, the leaching agent solution is prepared by mixing 450-550 parts by volume of deionized water, 18-24 parts by mass of tartaric acid, and 8-12 parts by mass of anhydrous sodium sulfate, stirring at room temperature until completely dissolved, placing in an ice bath, and adding 34-42 parts by volume of 98wt% concentrated sulfuric acid dropwise while continuously stirring. After the addition is completed, the mixture is cooled to room temperature and then diluted to 650-750 parts by volume with deionized water. The mixture is then stirred evenly to obtain the final solution.

[0013] During the preparation of the leachate, the strong exothermic process of adding concentrated sulfuric acid to water is controlled by ice bath cooling, which suppresses local overheating and ensures that the temperature rise of the solution is controllable when sulfuric acid is added dropwise.

[0014] Optionally, the organic phase mixture system is obtained by uniformly mixing 120-160 parts by volume of trioctylamine, 60-90 parts by volume of tributyl phosphate, and 450-520 parts by volume of sulfurized kerosene.

[0015] Optionally, in step S2, 180-220 parts by mass of zinc oxide waste are added to 500-700 parts by volume of deionized water, stirred at 55-65°C for 15-30 minutes, filtered, and then added to 700-900 parts by volume of sulfuric acid solution with a concentration of 0.3-0.7 mol / L. After strong stirring at 50-60°C for 15-35 minutes, the mixture is filtered to obtain zinc-rich pre-leaching solution and pre-leaching residue.

[0016] In step S2, after washing with water, a pre-leaching process using sulfuric acid is performed to remove zinc. The readily soluble zinc phases, such as ZnO, in the zinc oxide waste can preferentially dissolve under relatively mild sulfuric acid conditions to form a zinc-rich pre-leaching solution. Simultaneously, this process relatively enriches Te, Sn, and In in the solid phase, reducing the Zn content in the subsequent composite leaching solution. 2+ The concentration and zinc loading reduce the competition and interference of zinc on subsequent electrodeposition, extraction and precipitation separation.

[0017] Optionally, in step S3, the pre-leaching residue is added to the reactor, along with 650-750 parts by volume of leaching agent solution and calcium sulfate seed crystals. The temperature is raised to 75-85°C and vigorously stirred for 45-75 minutes. Subsequently, 8-15 parts by volume of hydrogen peroxide solution is added dropwise over a period of 5-15 minutes. During the addition, the temperature is maintained at 78-85°C and stirring is continued for 15-30 minutes before leaching is completed. The mixture is then filtered to obtain tellurium / tin / indium leaching solution and leaching residue.

[0018] Optionally, in step S3, the amount of calcium sulfate seed crystals used is 1 to 3 parts by mass, and the concentration of hydrogen peroxide solution is 25 to 35 wt%.

[0019] In step S3, adding hydrogen peroxide as an oxidation enhancement method can promote the transformation of some low-valence tellurium / tin-containing phases into more easily leached forms, improve the release and migration of target elements in the composite phase, and reduce the probability of "incomplete leaching" and "encapsulation residue".

[0020] Optionally, in step S4, the tellurium / tin / indium leaching solution is transferred to an electrolytic cell, and constant current electrodeposition is performed at 40~60°C using a graphite plate as the anode and a titanium plate as the cathode, with a current density of 50~100 A / m. 2Electrolyze for 50-110 minutes to preferentially reduce and deposit tellurium in the solution as elemental tellurium at the cathode; remove the cathode, scrape off the deposit, wash with deionized water 2-5 times, and dry at 60-80℃ to obtain tellurium powder and electrolyte.

[0021] Optionally, in step S5, the electrolyte is cooled to 20-35°C, and 650-750 parts by volume of organic phase mixture are added for extraction for 5-15 minutes. After standing and layering, the tin-enriched organic phase and raffinate are separated. The tin-enriched organic phase is washed 1-2 times with sulfuric acid solution of concentration 0.3-0.8 mol / L, and then back-extracted 1-3 times with sulfuric acid solution of concentration 1.5-2.5 mol / L. The back-extracts are combined to obtain tin-containing back-extract, which is then heated to 80-90°C and the pH is slowly adjusted to 0.9-1.4 with ammonia water. The mixture is kept warm and stirred for 45-90 minutes, filtered, washed, and calcined at 550-700°C for 1-3 hours to obtain tin oxide.

[0022] Optionally, in step S6, the raffinate is first heated to 45-60°C, and 160-240 parts by volume of oxalic acid solution is added with stirring, and the pH is adjusted to 1.6-2.4. The mixture is stirred at a constant temperature for 20-45 minutes, filtered, and zinc oxalate precipitate and filtrate are obtained. The zinc oxalate precipitate is washed with deionized water 1-3 times, added to 250-350 parts by volume of ammonium sulfide solution, stirred at 40-55°C for 45-90 minutes, filtered, and mixed with the filtrate to obtain an indium-containing leachate. Then, 0.5-5 parts by volume of hydrogen peroxide solution is added dropwise with stirring, and the pH is adjusted to 3.8-4.8 with ammonia water. The mixture is aged for 30-60 minutes, filtered, washed, dried at 70-90°C, and then calcined at 450-550°C for 1-3 hours to obtain indium oxide.

[0023] In step S6, zinc is further reduced by selective precipitation with oxalic acid, thus reducing the zinc content and reducing the zinc burden. 2+ The zinc oxalate precipitate is then further stirred and impregnated with ammonium sulfide solution. Any small amount of indium that may be present in the zinc oxalate precipitate is transferred into the indium-containing leachate to reduce the interference of zinc on subsequent indium recovery and avoid the risk of indium entrainment, thereby achieving enrichment and recovery.

[0024] Optionally, the concentration of the oxalic acid solution is 15-25 wt%, the concentration of the ammonium sulfide solution is 8-12 wt%, and the concentration of the hydrogen peroxide solution is 25-35 wt%.

[0025] The above-described technical solution of the present invention has at least the following beneficial effects: 1. This invention employs a composite leaching system with sulfuric acid as the main component, tartaric acid as the coordination regulating component, and anhydrous sodium sulfate to increase the sulfate content level. While providing stable acidity and sulfate medium, it regulates the liquid phase existence form of easily hydrolyzable metals such as tin through complexation and promotes the release of Te / Sn / In from the composite phase or encapsulated phase. The increased sulfate content level is conducive to the stabilization of impurities such as lead in the form of sulfate. Combined with calcium sulfate seed crystals to induce the orderly nucleation and growth of sulfate deposits, it can reduce fine particle suspension deposition and entrainment co-precipitation, improve filtration speed and filter cake permeability, and inhibit the risk of scaling, thereby taking into account leaching efficiency, selectivity and solid-liquid separation operability.

[0026] 2. This invention employs a sequential separation of tellurium first, then tin, and finally indium to reduce mutual interference among the metals. Tellurium is first removed by electrodeposition to solidify and prevent adsorption, entrainment, and loss during subsequent extraction or pH adjustment. After tellurium removal, solution interference is reduced and the acidic sulfate medium is maintained, which is beneficial for selective extraction and enrichment of tin using a trioctylamine-tributyl phosphate-sulfurized kerosene mixed system. The regulation of phase behavior by tributyl phosphate can inhibit emulsification and improve phase separation stability, thereby reducing the risk of co-extraction and facilitating subsequent hydrolysis and roasting to obtain tin dioxide.

[0027] 3. This invention constructs a stepwise recovery process of "composite leaching-electrodeposition-extraction-precipitation roasting" in a sulfate system, avoiding the strong corrosion and chloride accumulation / salt wastewater burden caused by using high acidity or chlorination systems, and realizing the separation, fixation and product recovery of tellurium, tin and indium within a relatively mild acidity and temperature window. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0029] Example 1 450 mL of deionized water, 18.0 g of tartaric acid, and 8.0 g of anhydrous sodium sulfate were mixed and stirred at room temperature until completely dissolved. The mixture was then placed in an ice bath, and 34.0 mL of 98 wt% concentrated sulfuric acid was added dropwise while continuously stirring. After the addition was complete, the mixture was cooled to room temperature and brought to a final volume of 650 mL with deionized water. The mixture was stirred thoroughly to obtain the leaching agent solution. 120 mL of trioctylamine, 60 mL of tributyl phosphate, and 450 mL of sulfurized kerosene were mixed thoroughly to obtain an organic phase mixture system.

[0030] 180g of zinc oxide waste was added to 500mL of deionized water and stirred at 55℃ for 15min. After filtration, the waste was added to 700mL of 0.3mol / L sulfuric acid solution and pre-leached at 50℃ with strong stirring for 15min. After filtration, zinc-rich pre-leaching solution and pre-leaching residue were obtained. The pre-leaching residue was added to a reaction vessel, along with 650mL of leaching agent solution and 1.0g of calcium sulfate seed crystals. The temperature was raised to 75℃ and stirred vigorously for 45min. Then, 8mL of 25wt% hydrogen peroxide solution was added dropwise over 5min. During the addition, the temperature was maintained at 78℃ and stirring was continued for 15min before leaching was stopped. After filtration, tellurium / tin / indium leaching solution and leaching residue were obtained.

[0031] The tellurium / tin / indium leaching solution was transferred to an electrolytic cell, and constant current electrodeposition was performed at 40°C using a graphite plate as the anode and a titanium plate as the cathode, with a current density of 50 A / m. 2 Electrolysis for 50 minutes allows tellurium in the solution to be preferentially reduced and deposited as elemental tellurium at the cathode. The cathode is removed, the deposit is scraped off, washed twice with deionized water, and dried at 60°C to obtain tellurium powder and electrolyte.

[0032] The electrolyte was cooled to 20°C, and 650 mL of organic phase mixture was added and extracted for 5 min. After standing and separating the layers, the tin-enriched organic phase and the raffinate were obtained. The tin-enriched organic phase was washed once with 0.3 mol / L sulfuric acid solution, and then back-extracted once with 1.5 mol / L sulfuric acid solution. The back-extracts were combined to obtain a tin-containing back-extract, which was then heated to 80°C and the pH was slowly adjusted to 0.9 with ammonia. The mixture was kept warm and stirred for 45 min, filtered and washed, and then calcined at 550°C for 1 h to obtain tin oxide.

[0033] The raffinate was heated to 45°C, and 160 mL of 15 wt% oxalic acid solution was added with stirring. The pH was adjusted to 1.6, and the mixture was stirred at a constant temperature for 20 min. After filtration, zinc oxalate precipitate and filtrate were obtained. The zinc oxalate precipitate was washed once with deionized water and then added to 250 mL of 8 wt% ammonium sulfide solution. After stirring at 40°C for 45 min, the mixture was filtered and mixed with the filtrate to obtain an indium-containing leachate. Then, 0.5 mL of 25 wt% hydrogen peroxide solution was added dropwise with stirring. The pH was then adjusted to 3.8 with ammonia water, and the mixture was aged for 30 min. After filtration and washing, the mixture was dried at 70°C and then calcined at 450°C for 1 h to obtain indium oxide.

[0034] Example 2 Mix 500 mL of deionized water, 21.0 g of tartaric acid, and 10.0 g of anhydrous sodium sulfate. Stir until completely dissolved at room temperature, then place in an ice bath. Add 38.0 mL of 98 wt% concentrated sulfuric acid dropwise while continuously stirring. After the addition is complete, continue cooling to room temperature and bring the volume to 700 mL with deionized water. Mix thoroughly to obtain the leaching agent solution. Mix 140 mL of trioctylamine, 75 mL of tributyl phosphate, and 485 mL of sulfurized kerosene thoroughly to obtain an organic phase mixture system.

[0035] 200g of zinc oxide waste was added to 600mL of deionized water and stirred at 60℃ for 20min. After filtration, the waste was added to 800mL of 0.5mol / L sulfuric acid solution and pre-leached at 55℃ with strong stirring for 25min. After filtration, zinc-rich pre-leaching solution and pre-leaching residue were obtained. The pre-leaching residue was added to a reaction vessel, along with 700mL of leaching agent solution and 2.0g of calcium sulfate seed crystals. The temperature was raised to 80℃ and stirred vigorously for 60min. Then, 12mL of 30wt% hydrogen peroxide solution was added dropwise over 10min. During the addition, the temperature was maintained at 82℃ and stirring was continued for 20min. The leaching was then stopped and filtered to obtain tellurium / tin / indium leaching solution and leaching residue.

[0036] The tellurium / tin / indium leaching solution was transferred to an electrolytic cell, and constant current electrodeposition was performed at 50°C using a graphite plate as the anode and a titanium plate as the cathode, with a current density of 70 A / m. 2 Electrolysis for 80 minutes allows tellurium in the solution to be preferentially reduced and deposited as elemental tellurium at the cathode. The cathode is removed, the deposit is scraped off, washed three times with deionized water, and dried at 70°C to obtain tellurium powder and electrolyte.

[0037] The electrolyte was cooled to 25°C, and 700 mL of organic phase mixture was added and extracted for 10 min. After standing and separating the layers, the tin-enriched organic phase and the raffinate were obtained. The tin-enriched organic phase was washed once with 0.5 mol / L sulfuric acid solution, and then back-extracted twice with 2.0 mol / L sulfuric acid solution. The back-extracts were combined to obtain a tin-containing back-extract, which was then heated to 85°C and the pH was slowly adjusted to 1.2 with ammonia. The mixture was kept warm and stirred for 60 min, filtered and washed, and then calcined at 650°C for 2 h to obtain tin oxide.

[0038] The raffinate was heated to 50°C, and 200 mL of 20 wt% oxalic acid solution was added with stirring. The pH was adjusted to 2.0, and the mixture was stirred at a constant temperature for 30 min. After filtration, zinc oxalate precipitate and filtrate were obtained. The zinc oxalate precipitate was washed twice with deionized water and then added to 300 mL of 10 wt% ammonium sulfide solution. After stirring at 45°C for 60 min, the mixture was filtered and mixed with the filtrate to obtain an indium-containing leachate. Then, 2.0 mL of 30 wt% hydrogen peroxide solution was added dropwise with stirring. The pH was then adjusted to 4.2 with ammonia water, and the mixture was aged for 45 min. After filtration and washing, the mixture was dried at 80°C and then calcined at 500°C for 2 h to obtain indium oxide.

[0039] Example 3 Mix 550 mL of deionized water, 24.0 g of tartaric acid, and 12.0 g of anhydrous sodium sulfate. Stir until completely dissolved at room temperature, then place in an ice bath. Add 42.0 mL of 98 wt% concentrated sulfuric acid dropwise while continuously stirring. After the addition is complete, continue cooling to room temperature and bring the volume to 750 mL with deionized water. Mix thoroughly to obtain the leaching agent solution. Mix 160 mL of trioctylamine, 90 mL of tributyl phosphate, and 520 mL of sulfurized kerosene thoroughly to obtain an organic phase mixture system.

[0040] 220g of zinc oxide waste was added to 700mL of deionized water and stirred at 65℃ for 30min. After filtration, it was added to 900mL of 0.7mol / L sulfuric acid solution and pre-leached at 60℃ with strong stirring for 35min. After filtration, zinc-rich pre-leaching solution and pre-leaching residue were obtained. The pre-leaching residue was added to a reaction vessel, along with 750mL of leaching agent solution and 3.0g of calcium sulfate seed crystals. The temperature was raised to 85℃ and stirred vigorously for 75min. Then, 15mL of 35wt% hydrogen peroxide solution was added dropwise over 15min. During the addition, the temperature was maintained at 85℃ and stirring was continued for 30min. The leaching was then stopped and filtered to obtain tellurium / tin / indium leaching solution and leaching residue.

[0041] The tellurium / tin / indium leaching solution was transferred into an electrolytic cell, and constant current electrodeposition was performed at 60°C using a graphite plate as the anode and a titanium plate as the cathode, with a current density of 100 A / m. 2 Electrolysis for 110 min allows tellurium in the solution to be preferentially reduced and deposited as elemental tellurium at the cathode. The cathode is removed, the deposit is scraped off, washed five times with deionized water, and dried at 80°C to obtain tellurium powder and electrolyte.

[0042] The electrolyte was cooled to 35°C, and 750 mL of organic phase mixture was added and extracted for 15 min. After standing and separating the layers, the tin-enriched organic phase and the raffinate were obtained. The tin-enriched organic phase was washed twice with 0.8 mol / L sulfuric acid solution, and then back-extracted three times with 2.5 mol / L sulfuric acid solution. The back-extracts were combined to obtain a tin-containing back-extract, which was then heated to 90°C and the pH was slowly adjusted to 1.4 with ammonia. The mixture was kept warm and stirred for 90 min, filtered and washed, and then calcined at 700°C for 3 h to obtain tin oxide.

[0043] The raffinate was heated to 60°C, and 240 mL of 25 wt% oxalic acid solution was added with stirring. The pH was adjusted to 2.4, and the mixture was stirred at a constant temperature for 45 min. After filtration, zinc oxalate precipitate and filtrate were obtained. The zinc oxalate precipitate was washed three times with deionized water and then added to 350 mL of 12 wt% ammonium sulfide solution. After stirring at 55°C for 90 min, the mixture was filtered and mixed with the filtrate to obtain an indium-containing leachate. Then, 5.0 mL of 35 wt% hydrogen peroxide solution was added dropwise with stirring. The pH was then adjusted to 4.8 with ammonia water, and the mixture was aged for 60 min. After filtration and washing, the mixture was dried at 90°C and then calcined at 550°C for 3 h to obtain indium oxide.

[0044] Example 4 470 mL of deionized water, 19.0 g of tartaric acid, and 9.0 g of anhydrous sodium sulfate were mixed and stirred at room temperature until completely dissolved. The mixture was then placed in an ice bath, and 35.0 mL of 98 wt% concentrated sulfuric acid was added dropwise with continuous stirring. After the addition was complete, the mixture was cooled to room temperature and brought to a final volume of 670 mL with deionized water. The mixture was stirred thoroughly to obtain the leaching agent solution. 130 mL of trioctylamine, 65 mL of tributyl phosphate, and 470 mL of sulfurized kerosene were mixed thoroughly to obtain an organic phase mixture. 190g of zinc oxide waste was added to 550mL of deionized water and stirred at 58℃ for 18min. After filtration, the solution was added to 760mL of 0.4mol / L sulfuric acid solution and pre-leached at 52℃ with vigorous stirring for 20min. After filtration, zinc-rich pre-leaching solution and pre-leaching residue were obtained. The pre-leaching residue was added to a reactor along with 670mL of leaching agent solution and 1.5g of calcium sulfate seed crystals. The temperature was raised to 78℃ and vigorously stirred for 55min. Then, 10mL of 30wt% hydrogen peroxide solution was added dropwise over 8min, maintaining the temperature at 80℃ and stirring for another 18min. The leaching was then stopped, and the solution was filtered to obtain tellurium / tin / indium leaching solution and leaching residue. The tellurium / tin / indium leaching solution was transferred to an electrolytic cell and subjected to constant current electrodeposition at 45℃ with a graphite plate as the anode and a titanium plate as the cathode at a current density of 60A / m. 2Electrolysis was performed for 65 min. The cathode was removed, the deposit was scraped off, washed three times with deionized water, and dried at 65 °C to obtain tellurium powder and electrolyte. The electrolyte was cooled to 25 °C, and 680 mL of organic phase mixture was added and extracted for 8 min. After standing and separating the layers, the tin-enriched organic phase and raffinate were obtained. The tin-enriched organic phase was washed once with 0.4 mol / L sulfuric acid solution, and then back-extracted twice with 1.8 mol / L sulfuric acid solution. The back-extracts were combined, heated to 83 °C, and the pH was slowly adjusted to 1.1 with ammonia water. The mixture was kept at this temperature and stirred for 55 min. After filtration and washing, the mixture was calcined at 600 °C for 2 h to obtain tin oxide. The raffinate was heated to 48°C, and 180 mL of 18 wt% oxalic acid solution was added with stirring. The pH was adjusted to 1.9, and the mixture was stirred at a constant temperature for 25 min. After filtration, zinc oxalate precipitate and filtrate were obtained. The zinc oxalate precipitate was washed twice with deionized water and then added to 280 mL of 9 wt% ammonium sulfide solution. After stirring at 43°C for 55 min, the mixture was filtered and mixed with the filtrate to obtain an indium-containing leachate. Then, 1.5 mL of 30 wt% hydrogen peroxide solution was added dropwise with stirring. The pH was then adjusted to 4.1 with ammonia water, and the mixture was aged for 40 min. After filtration and washing, the mixture was dried at 75°C and then calcined at 480°C for 2 h to obtain indium oxide.

[0045] Example 5 Mix 520 mL of deionized water, 22.0 g of tartaric acid, and 11.0 g of anhydrous sodium sulfate. Stir until completely dissolved at room temperature, then place in an ice bath. Add 40.0 mL of 98 wt% concentrated sulfuric acid dropwise while continuously stirring. After the addition is complete, continue cooling to room temperature and bring the volume to 720 mL with deionized water. Mix thoroughly to obtain the leaching agent solution. Mix 150 mL of trioctylamine, 80 mL of tributyl phosphate, and 500 mL of sulfurized kerosene thoroughly to obtain an organic phase mixture system.

[0046] 210g of zinc oxide waste was added to 650mL of deionized water and stirred at 62℃ for 25min. After filtration, the solution was added to 860mL of 0.6mol / L sulfuric acid solution and pre-leached at 58℃ with strong stirring for 30min. After filtration, zinc-rich pre-leaching solution and pre-leaching residue were obtained. The pre-leaching residue was added to a reaction vessel, along with 720mL of leaching agent solution and 2.5g of calcium sulfate seed crystals. The temperature was raised to 83℃ and stirred vigorously for 70min. Then, 14mL of 35wt% hydrogen peroxide solution was added dropwise over 12min. During the addition, the temperature was maintained at 84℃ and stirring was continued for 25min before leaching was stopped. After filtration, tellurium / tin / indium leaching solution and leaching residue were obtained.

[0047] The tellurium / tin / indium leaching solution was transferred into an electrolytic cell, and constant current electrodeposition was performed at 55°C using a graphite plate as the anode and a titanium plate as the cathode, with a current density of 90 A / m. 2Electrolysis was performed for 95 minutes. The cathode was removed, the deposit was scraped off, washed four times with deionized water, and dried at 75°C to obtain tellurium powder and electrolyte.

[0048] The electrolyte was cooled to 30°C, and 730 mL of organic phase mixture was added and extracted for 12 min. After standing and separating the layers, the tin-enriched organic phase and the raffinate were obtained. The tin-enriched organic phase was washed twice with 0.6 mol / L sulfuric acid solution, and then back-extracted twice with 2.2 mol / L sulfuric acid solution. The back-extracts were combined, heated to 88°C, and the pH was slowly adjusted to 1.3 with ammonia. The mixture was kept warm and stirred for 80 min, filtered, washed, and then calcined at 680°C for 3 h to obtain tin oxide.

[0049] The raffinate was heated to 55°C, and 220 mL of 22 wt% oxalic acid solution was added with stirring. The pH was adjusted to 2.2, and the mixture was stirred at a constant temperature for 40 min. After filtration, zinc oxalate precipitate and filtrate were obtained. The zinc oxalate precipitate was washed three times with deionized water and then added to 330 mL of 11 wt% ammonium sulfide solution. After stirring at 50°C for 80 min, the mixture was filtered and mixed with the filtrate to obtain an indium-containing leachate. Then, 3.5 mL of 35 wt% hydrogen peroxide solution was added dropwise with stirring. The pH was then adjusted to 4.6 with ammonia water, and the mixture was aged for 55 min. After filtration and washing, the mixture was dried at 85°C and then calcined at 530°C for 3 h to obtain indium oxide.

[0050] Example 6 490 mL of deionized water, 20.0 g of tartaric acid, and 9.5 g of anhydrous sodium sulfate were mixed and stirred at room temperature until completely dissolved. The mixture was then placed in an ice bath, and 37.0 mL of 98 wt% concentrated sulfuric acid was added dropwise while continuously stirring. After the addition was complete, the mixture was cooled to room temperature and brought to a final volume of 690 mL with deionized water. The mixture was stirred thoroughly to obtain the leaching agent solution. 135 mL of trioctylamine, 70 mL of tributyl phosphate, and 480 mL of sulfurized kerosene were mixed thoroughly to obtain an organic phase mixture system.

[0051] 205g of zinc oxide waste was added to 620mL of deionized water and stirred at 61℃ for 22min. After filtration, the solution was added to 820mL of 0.55mol / L sulfuric acid solution and pre-leached at 56℃ with strong stirring for 28min. After filtration, zinc-rich pre-leaching solution and pre-leaching residue were obtained. The pre-leaching residue was added to a reaction vessel, along with 690mL of leaching agent solution and 2.0g of calcium sulfate seed crystals. The temperature was raised to 81℃ and stirred vigorously for 65min. Then, 11mL of 30wt% hydrogen peroxide solution was added dropwise over 10min. During the addition, the temperature was maintained at 83℃ and stirring was continued for 22min before leaching was stopped. After filtration, tellurium / tin / indium leaching solution and leaching residue were obtained.

[0052] The tellurium / tin / indium leaching solution was transferred into an electrolytic cell, and constant current electrodeposition was performed at 52°C using a graphite plate as the anode and a titanium plate as the cathode, with a current density of 80 A / m. 2 Electrolysis was performed for 90 minutes. The cathode was removed, the deposit was scraped off, washed four times with deionized water, and dried at 72°C to obtain tellurium powder and electrolyte.

[0053] The electrolyte was cooled to 28°C, and 700 mL of organic phase mixture was added and extracted for 10 min. After standing and separating the layers, the tin-enriched organic phase and the raffinate were obtained. The tin-enriched organic phase was washed once with 0.5 mol / L sulfuric acid solution, and then back-extracted twice with 2.0 mol / L sulfuric acid solution. The back-extracts were combined, heated to 86°C, and the pH was slowly adjusted to 1.2 with ammonia. The mixture was kept warm and stirred for 70 min, filtered, washed, and then calcined at 650°C for 2 h to obtain tin oxide.

[0054] The raffinate was heated to 52°C, and 210 mL of 20 wt% oxalic acid solution was added with stirring. The pH was adjusted to 2.1, and the mixture was stirred at a constant temperature for 35 min. After filtration, zinc oxalate precipitate and filtrate were obtained. The zinc oxalate precipitate was washed twice with deionized water and then added to 310 mL of 10 wt% ammonium sulfide solution. After stirring at 48°C for 70 min, the mixture was filtered and mixed with the filtrate to obtain an indium-containing leachate. Then, 2.5 mL of 30 wt% hydrogen peroxide solution was added dropwise with stirring. The pH was then adjusted to 4.3 with ammonia water, and the mixture was aged for 50 min. After filtration and washing, the mixture was dried at 82°C and then calcined at 520°C for 2 h to obtain indium oxide.

[0055] The present invention also includes comparative examples and related experiments.

[0056] Comparative Example 1 Compared with Example 2, the only difference is that tartaric acid was not added to the leaching agent solution. The other preparation steps and components are completely consistent, and the recovery of tellurium, tin and indium is finally completed.

[0057] Comparative Example 2 Compared with Example 2, the only difference is that tributyl phosphate was not added to the organic phase mixture system. The other preparation steps and components were completely consistent, and the recovery of tellurium, tin and indium was finally completed.

[0058] Comparative Example 3 Compared with Example 2, the only difference is that calcium sulfate seed crystals were not added during the recovery process. The other preparation steps and components were completely consistent, and the recovery of tellurium, tin and indium was finally completed.

[0059] Performance testing The zinc oxide waste used in Examples 1-6 and Comparative Examples 1-3, as well as the finally recovered tellurium powder, tin oxide, and indium oxide, were microwave digested according to HJ832-2017 "Microwave Digestion Method for Total Metal Elements in Soil and Sediments". After cooling, the solutions were diluted to volume, filtered / centrifuged to obtain the test solutions. The test solutions were then analyzed and calculated using HJ700-2014 "Inductively Coupled Plasma Mass Spectrometry for the Determination of 65 Elements in Water" to obtain the purity and recovery rate. The specific purity test results are shown in Table 1, and the recovery rate test results are shown in Table 2.

[0060] Table 1

[0061] Table 2

[0062] As shown in Tables 1 and 2, all six examples of this invention can obtain high-purity tellurium powder, tin oxide, and indium oxide, and achieve high Te / Sn / In recovery rates. Compared with Comparative Example 1, the purity and recovery rate of tellurium powder, tin oxide, and indium oxide are significantly improved after the addition of tartaric acid, indicating that tartaric acid has a weakening effect on impurity interference in the leaching system. Compared with Comparative Example 2, the Sn recovery rate and tin oxide purity are significantly improved after the introduction of tributyl phosphate into the mixed extraction system, indicating that tributyl phosphate plays a key role in improving the selectivity of tin extraction and separation, inhibiting entrainment, and stabilizing phase behavior. Compared with Comparative Example 3, the addition of calcium sulfate seeds can improve solid-liquid separation conditions and reduce entrainment loss, thereby improving recovery rate and purity.

[0063] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for recovering tellurium, tin, and indium from zinc oxide waste, characterized in that, Includes the following steps: S1. Mix deionized water, tartaric acid, anhydrous sodium sulfate, and concentrated sulfuric acid to prepare an leaching agent solution; mix trioctylamine, tributyl phosphate, and sulfurized kerosene to obtain an organic phase mixture system. S2. Add zinc oxide waste to deionized water, stir, filter, and obtain pre-leaching residue; S3. Add the pre-leaching residue to the leaching agent solution and add calcium sulfate seed crystals, heat and stir, add hydrogen peroxide and continue stirring to leach, filter to obtain tellurium / tin / indium leaching solution and leaching residue; S4. The tellurium / tin / indium leaching solution is placed in an electrodeposition apparatus for electrodeposition, the cathode deposit is recovered, tellurium powder is obtained, and an electrolyte is obtained. S5. Mix the electrolyte and organic phase mixture system for extraction, allow it to stand and separate into layers, and separate the tin-enriched organic phase and raffinate; wash and back-extract the tin-enriched organic phase to obtain a tin-containing back-extract, hydrolyze it to obtain a tin-containing precipitate, and calcine it to obtain tin dioxide. S6. Add hydrogen peroxide solution to the raffinate, adjust the pH, age, dry, and calcine to obtain indium oxide.

2. The method for recovering tellurium, tin, and indium from zinc oxide waste according to claim 1, characterized in that, The leaching agent solution is prepared by mixing 450-550 parts by volume of deionized water, 18-24 parts by mass of tartaric acid, and 8-12 parts by mass of anhydrous sodium sulfate, stirring at room temperature until completely dissolved, and then placing it in an ice bath. Under continuous stirring, 34-42 parts by volume of 98wt% concentrated sulfuric acid is added dropwise. After the addition is completed, the mixture is cooled to room temperature and then diluted to 650-750 parts by volume with deionized water. The mixture is then stirred evenly to obtain the final solution.

3. The method for recovering tellurium, tin, and indium from zinc oxide waste according to claim 1, characterized in that, The organic phase mixture system is obtained by uniformly mixing 120-160 parts by volume of trioctylamine, 60-90 parts by volume of tributyl phosphate, and 450-520 parts by volume of sulfurized kerosene.

4. The method for recovering tellurium, tin, and indium from zinc oxide waste according to claim 1, characterized in that, In step S2, 180-220 parts by mass of zinc oxide waste are added to 500-700 parts by volume of deionized water, stirred at 55-65°C for 15-30 minutes, filtered, and then added to 700-900 parts by volume of sulfuric acid solution with a concentration of 0.3-0.7 mol / L. After strong stirring at 50-60°C for 15-35 minutes, the mixture is filtered to obtain zinc-rich pre-leaching solution and pre-leaching residue.

5. The method for recovering tellurium, tin, and indium from zinc oxide waste according to claim 1, characterized in that, In step S3, the pre-leaching residue is added to the reactor, along with 650-750 parts by volume of leaching agent solution and calcium sulfate seed crystals. The temperature is raised to 75-85°C and vigorously stirred for 45-75 minutes. Then, 8-15 parts by volume of hydrogen peroxide solution is added dropwise over a period of 5-15 minutes. During the addition, the temperature is maintained at 78-85°C and stirring is continued for 15-30 minutes before leaching is completed. The mixture is then filtered to obtain tellurium / tin / indium leaching solution and leaching residue.

6. The method for recovering tellurium, tin, and indium from zinc oxide waste according to claim 5, characterized in that, In step S3, the amount of calcium sulfate seed crystals used is 1-3 parts by mass, and the concentration of hydrogen peroxide solution is 25-35 wt%.

7. The method for recovering tellurium, tin, and indium from zinc oxide waste according to claim 1, characterized in that, In step S4, the tellurium / tin / indium leaching solution is transferred into an electrolytic cell, and constant current electrodeposition is performed at 40-60°C using a graphite plate as the anode and a titanium plate as the cathode, with a current density of 50-100 A / m. 2 Electrolyze for 50-110 minutes to preferentially reduce and deposit tellurium in the solution as elemental tellurium at the cathode; remove the cathode, scrape off the deposit, wash with deionized water 2-5 times, and dry at 60-80℃ to obtain tellurium powder and electrolyte.

8. The method for recovering tellurium, tin, and indium from zinc oxide waste according to claim 1, characterized in that, In step S5, the electrolyte is cooled to 20~35℃, 650~750 volumes of organic phase mixture system are added and mixed for 5~15 min, allowed to stand and separate into layers, and tin-enriched organic phase and raffinate are obtained. The tin-enriched organic phase is washed 1-2 times with a sulfuric acid solution of 0.3-0.8 mol / L, then back-extracted 1-3 times with a sulfuric acid solution of 1.5-2.5 mol / L. The back-extracts are combined to obtain a tin-containing back-extract, which is then heated to 80-90℃ and the pH is slowly adjusted to 0.9-1.4 with ammonia. The mixture is kept warm and stirred for 45-90 min, filtered, washed, and calcined at 550-700℃ for 1-3 h to obtain tin oxide.

9. A method for recovering tellurium, tin, and indium from zinc oxide waste according to claim 1, characterized in that, In step S6, the raffinate is first heated to 45-60°C, and 160-240 parts by volume of oxalic acid solution is added with stirring. The pH is adjusted to 1.6-2.4, and the mixture is stirred at a constant temperature for 20-45 minutes. After filtration, zinc oxalate precipitate and filtrate are obtained. After washing the zinc oxalate precipitate 1-3 times with deionized water, add it to 250-350 parts by volume of ammonium sulfide solution, stir at 40-55℃ for 45-90 min, filter, and mix with the filtrate to obtain an indium-containing leachate. Then, add 0.5-5 parts by volume of hydrogen peroxide solution dropwise while stirring, adjust the pH to 3.8-4.8 with ammonia water, age for 30-60 min, filter, wash, dry at 70-90℃, and then calcine at 450-550℃ for 1-3 h to obtain indium oxide.

10. A method for recovering tellurium, tin, and indium from zinc oxide waste according to claim 9, characterized in that, The concentration of the oxalic acid solution is 15-25 wt%, the concentration of the ammonium sulfide solution is 8-12 wt%, and the concentration of the hydrogen peroxide solution is 25-35 wt%.

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