Method for preparing high-purity tellurium dioxide powder from refined tellurium slag

Abstract

The invention provides a method for preparing high-purity tellurium dioxide powder from refined tellurium slag, and belongs to a deep processing technology of a rare and dispersed element tellurium in the field of nonferrous metallurgy. According to the technical scheme, the method comprises the following steps. The method comprises the steps of tellurium slag water leaching, water leaching liquid impurity removal, solution complexing pretreatment, crude tellurium dioxide neutralization and precipitation with sulfuric acid, crude tellurium dioxide dissolution with concentrated hydrochloric acid, tellurium reduction with sodium sulfite, tellurium oxide powder oxidation with nitric acid, tellurium dioxide dissolution with concentrated hydrochloric acid, tellurium dioxide neutralization and precipitation with a refined tellurium tetrachloride solution, water washing and high-temperature calcination. By means of the steps, the tellurium dioxide powder with the chemical purity meeting the requirements of TeO2 99.90 or TeO2 99.50 of YS / T 1194-2017 tellurium dioxide and the average particle size D50 ranging from 40 micrometers to 75 micrometers can be prepared through the technology, and the tellurium dioxide powder with the chemical purity meeting the TeO2 99.90 or TeO2 99.50 brand requirements of YS / T 1194-2017 tellurium dioxide. In the whole process, the tellurium slag with high impurity content can be used as a raw material, and the impurity content can be effectively removed without electrodeposition of refined tellurium, so that tellurium dioxide is refined. And the process conditions are mild, the equipment is simple, the operation is simple and convenient, and the production period is short.

Description

Technical Field

[0001] The invention belongs to the field of nonferrous metallurgy, and further belongs to the technical field of deep processing of scattered element tellurium, and in particular relates to a method for preparing high-purity tellurium dioxide powder by refining tellurium slag. Background Art

[0002] Tellurium slag produced during the pyrometallurgical smelting of copper anode mud and lead anode mud is an important raw material for tellurium extraction. It is currently mainly used to produce tellurium ingots. The process is tellurium slag water leaching or alkaline leaching - Na2S impurity removal - neutralization precipitation of TeO2 - alkaline dissolution - Na2S, CaCl2 purification - secondary neutralization precipitation of TeO2 - alkaline dissolution - electrolysis to obtain refined tellurium.

[0003] Using refined tellurium as raw material, various tellurium-containing fine chemical products can be further produced. Among them, tellurium dioxide powder (see "YS / T 1194-2017 Tellurium Dioxide") with a certain particle size and purity is an important chemical raw material used in electronic components, preservatives, rubber additives, electroplating brighteners and other fields. At present, the production process is mainly a wet process, such as tellurium ingot crushing-aqua regia dissolution-neutralization precipitation of tellurium dioxide-calcination method (CN106542508A).

[0004] In order to reduce production costs, researchers in recent years have tried to directly purify tellurium dioxide using smelting raw materials with lower purity.

[0005] Ma Yutian et al. used crude tellurium powder as raw material, and prepared tellurium dioxide powder with a purity greater than 99.9% through a process of nitric acid oxidation - filter residue washing - sodium hydroxide dissolution of the washed residue - alkaline solution plus sulfuric acid neutralization to precipitate tellurium dioxide, but did not specify the impurity content (CN101259956A).

[0006] He Congxing studied the process of tellurium slag water leaching - neutralization precipitation of TeO2 - sodium hydroxide dissolution of TeO2 - Na2S precipitation of heavy metal ions, EDTA complexation removal of impurities - sulfuric acid secondary neutralization precipitation of TeO2. The TeO2 content was not less than 99.5% (only the impurity Cu 0.005% was reported), and the product TeO2 recovery rate was 76% (He Congxing. Nonferrous Metallurgy, 2001(1):41-42.).

[0007] Wu Yuangui et al. studied the process of tellurium slag water leaching - sulfuric acid neutralization precipitation of TeO2 - sodium hydroxide dissolution of TeO2 - sulfuric acid secondary neutralization precipitation of TeO2, the product TeO2 content is 99.2% (Wu Yuangui, et al. Shanghai Nonferrous Metals, 2012, 33(2): 59-61.).

[0008] At present, there is no report on the process of directly preparing tellurium dioxide powder with purity and particle size meeting the requirements of "YS / T 1194-2017 Tellurium Dioxide" using tellurium slag as raw material. Summary of the invention

[0009] The object of the present invention is to provide a method for preparing high-purity tellurium dioxide powder by refining tellurium slag.

[0010] The object of the present invention is achieved in that the method for preparing high-purity tellurium dioxide powder by refining tellurium slag comprises pre-treatment, main reaction and post-treatment steps, specifically comprising: A. Pre-treatment: 1) The tellurium slag to be treated is crushed to a particle size of -75 μm accounting for more than 90%, and water leaching liquid a and water leaching slag b are obtained through slurry mixing, water leaching and filtration, and the water leaching slag b is stored; 2) The water extract a is heated to 40-90°C, sodium sulfide and calcium chloride are added, and the mixture is stirred and reacted at a temperature of 40-90°C for 0.5-3h, and the impurity-removed liquid c and impurity-removed slag d are obtained by liquid-solid separation, and the impurity-removed slag d is stored; B. Main reaction: 1) Add EDTA to the impurity-removed liquid c, heat it to 40-100°C and stir it for 5-30 minutes, then slowly drop sulfuric acid solution at 40-100°C until the pH is 5-7, continue to stir the reaction at 40-100°C for 0.5-1h, and obtain crude tellurium dioxide e and neutralization tail liquid through liquid-solid separation, and the neutralization tail liquid enters wastewater treatment; 2) Add concentrated hydrochloric acid to the crude tellurium dioxide e, react at a temperature of 30-80°C for 10-60 minutes, and obtain a crude tellurium tetrachloride solution f and an insoluble slag through liquid-solid separation, and the insoluble slag is stored; 3) Sodium sulfite is added to the crude tellurium tetrachloride solution f, and the mixture is stirred for 0.5-1h to obtain metal tellurium powder g and neutralization tail liquid by liquid-solid separation. The neutralization tail liquid is then used for wastewater treatment; 4) Add distilled water to the metal tellurium powder g to prepare a slurry, then add concentrated nitric acid and stir to react, and obtain tellurium dioxide h and oxidation tail liquid through liquid-solid separation, and the oxidation tail liquid is returned to step 1); 5) Add concentrated hydrochloric acid to tellurium dioxide h, react at a temperature of 30-80°C for 10-60 minutes, and obtain a refined tellurium tetrachloride solution i and an insoluble residue by liquid-solid separation. The insoluble residue is returned to step 4); C. Post-processing: 1) The refined tellurium tetrachloride solution i is heated to 35-90°C, and then ammonia water or sodium bicarbonate solution is added dropwise until the pH is 5-6, and the reaction is stirred for 0.4-0.6h. The refined tellurium dioxide j and the neutralization tail liquid are obtained by liquid-solid separation, and the neutralization tail liquid is sent to the wastewater treatment; 2) Add distilled water to the refined tellurium dioxide and stir and wash at a temperature of 40-60°C for 20-40 minutes. The filter cake is dried and calcined to obtain the target high-purity tellurium dioxide with an average particle size of 45-75 μm.

[0011] The specific operations are as follows: S1) Water leaching of tellurium slag. The reaction conditions are: the tellurium slag is crushed to a particle size of -75 microns accounting for more than 90%, and then slurried with tap water, stirred and leached for 1 hour at a liquid-to-solid ratio (L / kg) of 2-3:1 and 50-100°C. Filter to prepare water leaching liquid and water leaching slag, which are stored.

[0012] S2) Decontamination of water infusion. The reaction conditions are: the water infusion obtained in step S1 is heated to 40-90°C, and then sodium sulfide (industrial pure) containing 2-30g Na2S and calcium chloride (industrial pure) containing 0.5-20g CaCl2 are added to each liter of water infusion, and the reaction is stirred for 0.5-3h, and the reaction temperature is kept at 40-90°C. After the reaction is completed, the liquid and solid are separated to obtain the decontaminated liquid and decontaminated slag, and the decontaminated slag is stored.

[0013] S3) Solution complexation pretreatment - sulfuric acid neutralization to precipitate crude tellurium dioxide. The reaction conditions are: add 5-20g / L analytically pure solid EDTA to the impurity-removed liquid obtained in step S2, heat to 40-100°C and stir for 5-30min; then slowly drip a 15%-40% sulfuric acid solution (prepared with metallurgical grade concentrated sulfuric acid and tap water) at a constant temperature of 40-100°C until the slurry pH is 5-7, then continue to stir at a constant temperature for 0.5-1h, and the reaction is completed. Liquid-solid separation to obtain crude tellurium dioxide and neutralization tail liquid.

[0014] S4) Dissolve the crude tellurium dioxide with concentrated hydrochloric acid and reduce the tellurium with sodium sulfite. Add 1.1-1.4 times the stoichiometric concentration of 36%-38% industrial pure concentrated hydrochloric acid to the crude tellurium dioxide obtained in step S4, and stir the reaction at a reaction temperature of 30-80°C and a reaction time of 10-60min until the white tellurium dioxide particles are no longer visible to the naked eye. Liquid-solid separation, the filtrate is a crude tellurium tetrachloride solution. Then slowly add analytical pure sodium sulfite solid to the crude tellurium tetrachloride solution at 50-90°C, and continue stirring the reaction for 0.5-1h after the addition. The amount of sodium sulfite added is 2.5-3.5 times the mass of tellurium metal in the crude tellurium tetrachloride solution. After the reaction is completed, liquid-solid separation is performed to obtain metallic tellurium powder.

[0015] S5) Oxidation of tellurium powder with nitric acid. Add distilled water to the tellurium powder obtained in step S4 to make a slurry with a liquid-solid ratio (L / kg) of 2:1 and heat to 15-90°C. Then, while stirring, slowly add analytical pure concentrated nitric acid until the black metal tellurium powder is no longer visible to the naked eye. Finally, continue stirring and reacting for 0.5-1.5 hours. After the reaction is completed, liquid and solid are separated to obtain oxidation tail liquid and tellurium dioxide.

[0016] S6) Dissolve tellurium dioxide with concentrated hydrochloric acid. Add 1.1-1.3 times the stoichiometric concentration of 36%-38% analytically pure hydrochloric acid to the tellurium dioxide obtained in step S5, stir and react at a reaction temperature of 30-80°C for 10-60 minutes until white tellurium dioxide particles are no longer visible to the naked eye. Liquid-solid separation is performed, and the filtrate is a refined tellurium tetrachloride solution.

[0017] S7) Neutralize the refined tellurium tetrachloride solution to precipitate tellurium dioxide. Heat the refined tellurium tetrachloride solution obtained in step S6 to 35-90°C, then slowly drop ammonia water (prepared with analytical grade ammonia water) with a concentration of 10%-28% or sodium bicarbonate solution (prepared with analytical grade sodium bicarbonate) with a concentration of 30-90g / L until the slurry pH is 5-6, and then continue to stir and react for 0.5h. After the reaction is completed, liquid-solid separation is performed to obtain refined tellurium dioxide and neutralization tail liquid.

[0018] S8) Water washing-high temperature calcination. The refined tellurium dioxide obtained in step S7 is washed with distilled water at a liquid-solid ratio (L / kg) of 5:1 at 50°C for 30 minutes, and the liquid and solid are separated. The filter cake is dried and calcined in air at 600°C for 2 hours. The chemical purity of the tellurium dioxide product finally meets the requirements of TeO299.90 or TeO299.50 in "YS / T 1194-2017 Tellurium Dioxide", and the average particle size D50 is between 40-75 microns.

[0019] Compared with the existing process, the present invention has the following advantages: (1) It can use tellurium slag with high impurity content as raw material, and can effectively remove the impurity content without electroplating refined tellurium, thereby refining tellurium dioxide. (2) The process conditions of the present invention are relatively mild, the equipment is simple, the operation is easy, and the production cycle is short.

[0020] The process of the present invention can prepare tellurium dioxide powder with a chemical purity that meets the requirements of TeO299.90 or TeO299.50 grades of "YS / T 1194-2017 Tellurium Dioxide" and an average particle size D50 between 40 and 75 microns. The entire process can use tellurium slag with high impurity content as raw material, and can effectively remove the impurity content without electrodeposition of refined tellurium, thereby refining tellurium dioxide. In addition, the process conditions are relatively mild, the equipment is simple, the operation is simple, and the production cycle is short. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0023] The method for preparing high-purity tellurium dioxide powder by refining tellurium slag of the present invention comprises pre-treatment, main reaction and post-treatment steps, specifically comprising: A. Pre-treatment: 1) The tellurium slag to be treated is crushed to a particle size of -75 μm accounting for more than 90%, and water leaching liquid a and water leaching slag b are obtained through slurry mixing, water leaching and filtration, and the water leaching slag b is stored; 2) The water extract a is heated to 40-90°C, sodium sulfide and calcium chloride are added, and the mixture is stirred and reacted at a temperature of 40-90°C for 0.5-3h, and the impurity-removed liquid c and impurity-removed slag d are obtained by liquid-solid separation, and the impurity-removed slag d is stored; B. Main reaction: 1) Add EDTA to the impurity-removed liquid c, heat it to 40-100°C and stir it for 5-30 minutes, then slowly drop sulfuric acid solution at 40-100°C until the pH is 5-7, continue to stir the reaction at 40-100°C for 0.5-1h, and obtain crude tellurium dioxide e and neutralization tail liquid through liquid-solid separation, and the neutralization tail liquid enters wastewater treatment; 2) Add concentrated hydrochloric acid to the crude tellurium dioxide e, react at a temperature of 30-80°C for 10-60 minutes, and obtain a crude tellurium tetrachloride solution f and an insoluble slag through liquid-solid separation, and the insoluble slag is stored; 3) Sodium sulfite is added to the crude tellurium tetrachloride solution f, and the mixture is stirred for 0.5-1h to obtain metal tellurium powder g and neutralization tail liquid by liquid-solid separation. The neutralization tail liquid is then used for wastewater treatment; 4) Add distilled water to the metal tellurium powder g to prepare a slurry, then add concentrated nitric acid and stir to react, and obtain tellurium dioxide h and oxidation tail liquid through liquid-solid separation, and the oxidation tail liquid is returned to step 1); 5) Add concentrated hydrochloric acid to tellurium dioxide h, react at a temperature of 30-80°C for 10-60 minutes, and obtain a refined tellurium tetrachloride solution i and an insoluble residue by liquid-solid separation. The insoluble residue is returned to step 4); C. Post-processing: 1) The refined tellurium tetrachloride solution i is heated to 35-90°C, and then ammonia water or sodium bicarbonate solution is added dropwise until the pH is 5-6, and the reaction is stirred for 0.4-0.6h. The refined tellurium dioxide j and the neutralization tail liquid are obtained by liquid-solid separation, and the neutralization tail liquid is sent to the wastewater treatment; 2) Add distilled water to the refined tellurium dioxide and stir and wash at a temperature of 40-60°C for 20-40 minutes. The filter cake is dried and calcined to obtain the target high-purity tellurium dioxide with an average particle size of 45-75 μm.

[0024] The refined tellurium slag is the tellurium slag obtained by pyrometallurgical smelting of copper anode mud and lead anode mud.

[0025] The water leaching described in step A 1) is carried out at a liquid-to-solid ratio of L / Kg (2-3):1 and a temperature of 50-100°C with stirring for 50-70 minutes.

[0026] In step A2), the amount of sodium sulfide added is 2-30 g / L; the amount of calcium chloride added is 0.5-20 g / L.

[0027] B. The amount of EDTA added in step 1) is 5-20 g / L; the mass percentage concentration of the sulfuric acid solution is 15-40%.

[0028] B. Adding distilled water to prepare the slurry and then adding concentrated nitric acid to stir the reaction as described in step 4) is to add distilled water to the metal tellurium powder g to prepare the slurry to a liquid-solid ratio of L / Kg of (1.5~2.5):1 and heat it to 15~90°C, then slowly add concentrated nitric acid while stirring until the black metal tellurium powder is no longer visible to the naked eye, and continue to stir the reaction for 0.5~1.5h.

[0029] C. The mass percentage concentration of the ammonia water described in step 1) is 10-28%.

[0030] C. The concentration of the sodium bicarbonate solution described in step 1) is 30-90 g / L.

[0031] C. The calcination in step 2) is carried out at 500-700°C in air.

[0032] C. The calcination time in step 2) is 1 to 3 hours.

[0033] The present invention is further described below with specific implementation cases: Example 1 Ⅰ: The tellurium slag is crushed to -75 microns and accounts for 92%, then tap water is added to make a slurry with a liquid-solid ratio (L / kg) of 3:1, and stirred at a constant temperature of 80℃ for 1 hour. After the reaction is completed, filter and prepare the water extract and water extract residue.

[0034] II: Add 3.5g of sodium sulfide solid (industrial pure) and 0.5g of industrial pure calcium chloride solid to the 80℃ water extract per liter of water extract, and then stir and react at constant temperature for 0.5h. After the reaction is completed, separate the liquid and solid to obtain the impurity-free liquid and impurity-free residue.

[0035] III: First, add 7g / L analytically pure solid EDTA to the impurity-removed liquid at 80°C and stir for 10 minutes; then slowly drip 15% sulfuric acid solution (prepared with metallurgical grade concentrated sulfuric acid and tap water) until the slurry pH is 5-6, and keep the temperature at 80°C; finally, continue to stir and react at 80°C for 1 hour. After the reaction is completed, liquid and solid are separated to obtain crude tellurium dioxide and neutralized tail liquid.

[0036] IV: Add 1.1 times the stoichiometric amount of 36%-38% industrial pure hydrochloric acid to the crude tellurium dioxide obtained in step III, stir the reaction at a reaction temperature of 60°C for 30 minutes. Liquid-solid separation, the filtrate is a crude tellurium tetrachloride solution. Then slowly add analytical pure sodium sulfite solid to the crude tellurium tetrachloride solution at 85°C, continue stirring and react for 1 hour after the addition, and the amount of sodium sulfite added is 2.5 times the mass of tellurium metal in the crude tellurium tetrachloride solution. After the reaction is completed, liquid-solid separation is performed to obtain tellurium powder.

[0037] V: Add distilled water to the tellurium powder to make a liquid-solid ratio (L / kg) of 2:1 and heat it to 20°C. Then, while stirring, slowly add analytical pure concentrated nitric acid until the black metal tellurium powder is no longer visible to the naked eye. Finally, continue to stir and react for 1.5 hours. After the reaction is completed, the liquid and solid are separated to obtain oxidation tail liquid and tellurium dioxide. The oxidation tail liquid is returned to step III as a neutralizer to replace or supplement sulfuric acid and used as a neutralizer for precipitating crude tellurium dioxide, which can further reduce the cost of chemical reagents in the process and reduce the amount of wastewater treatment.

[0038] VI: Add 36%-38% analytically pure hydrochloric acid at a concentration of 1.15 times the stoichiometric amount to the tellurium dioxide obtained in step V, and stir the reaction at a reaction temperature of 50° C. for 30 minutes. Liquid-solid separation is performed, and the filtrate is a refined tellurium tetrachloride solution.

[0039] VII: Heat the refined tellurium tetrachloride solution to 60°C, slowly add 10% ammonia solution (prepared with analytical grade ammonia) into it under stirring until the slurry pH is 5-6, and then continue to stir and react at constant temperature for 0.5h. After the reaction is completed, liquid-solid separation is performed to obtain refined tellurium dioxide and neutralization tail liquid.

[0040] VIII: Add distilled water to the refined tellurium dioxide at a liquid-to-solid ratio (L / kg) of 5:1 and stir and wash at 50°C for 30 minutes to separate the liquid and solid. The filter cake is dried and calcined in air at 600°C for 2 hours. The chemical purity of the final tellurium dioxide product meets the TeO2 99.50 grade of "YS / T 1194-2017 Tellurium Dioxide" and the average particle size D50 is 55 microns.

[0041] Example 2 Tellurium slag was treated according to steps I to VI of Example 1 to prepare a refined tellurium tetrachloride solution.

[0042] VII: Heat the refined tellurium tetrachloride solution to 60°C, slowly drop a 30g / L sodium bicarbonate solution (prepared with analytical grade sodium bicarbonate) into it under stirring until the slurry pH is 5-6, and then continue to stir and react for 0.5 h. After the reaction is completed, liquid-solid separation is performed to obtain refined tellurium dioxide and precipitated tail liquid.

[0043] VIII: Add distilled water to the refined tellurium dioxide at a liquid-to-solid ratio (L / kg) of 5:1 and stir and wash at 50°C for 30 minutes to separate the liquid and solid. The filter cake is dried and calcined in air at 600°C for 2 hours. The chemical purity of the final tellurium dioxide product meets the TeO2 99.50 grade of "YS / T 1194-2017 Tellurium Dioxide" and the average particle size D50 is 72 microns.

[0044] Example 3 Ⅰ: The tellurium slag is crushed to -75 microns and accounts for 91%, then tap water is added to make a slurry with a liquid-solid ratio (L / kg) of 5:1, and stirred at a constant temperature of 90°C for 1 hour. After the reaction is completed, filter and prepare the water extract and water extract residue.

[0045] II: The water infusion is heated to 90°C, and then solid sodium sulfide (industrial pure) and solid calcium chloride (industrial pure) are added at the rate of 5g Na2S and 0.7g CaCl2 per liter of water infusion, respectively, and stirred at a constant temperature for 0.5h. After the reaction is completed, the liquid and solid are separated to obtain the impurity-free liquid and impurity-free residue.

[0046] III: Add 10g / L analytically pure EDTA to the impurity-removed liquid, heat to 80℃ and stir for 20min; slowly drip 30% sulfuric acid solution (prepared with metallurgical grade concentrated sulfuric acid and tap water) until the slurry pH is 5-6; finally, continue to stir and react for 1h. After the reaction is completed, liquid-solid separation is performed to obtain crude tellurium dioxide and neutralized tail liquid.

[0047] IV: Add 1.2 times the stoichiometric concentration of 36%-38% industrial pure hydrochloric acid to the crude tellurium dioxide obtained in step III, at a reaction temperature of 80°C and a reaction time of 60 minutes. Liquid-solid separation, the filtrate is a crude tellurium tetrachloride solution. Then slowly add analytically pure sodium sulfite solid to the crude tellurium tetrachloride solution at 70°C, continue stirring and reacting for 0.5 hours after the addition, and the amount of sodium sulfite added is 3.0 times the mass of tellurium metal in the crude tellurium tetrachloride solution. After the reaction is completed, liquid-solid separation is performed to obtain metallic tellurium powder.

[0048] V: Add distilled water to the obtained tellurium powder to make a liquid-solid ratio (L / kg) of 2:1 and heat to 40°C. Then, slowly add analytical pure concentrated nitric acid while stirring until the black metal tellurium powder is no longer visible to the naked eye. Finally, continue stirring and reacting for 1 hour. After the reaction is completed, liquid and solid are separated to obtain oxidation tail liquid and tellurium dioxide.

[0049] VI: Add 36%-38% analytically pure hydrochloric acid at a concentration of 1.2 times the stoichiometric amount to the tellurium dioxide obtained in step V, react at a temperature of 30-80°C for 10-60 minutes, separate the liquid and solid, and the filtrate is a refined tellurium tetrachloride solution.

[0050] VII: Under stirring conditions, slowly add 10% ammonia solution (prepared with analytical grade ammonia) to the 60°C pure tellurium tetrachloride solution until the slurry pH is 5-6, and then continue to stir and react at constant temperature for 0.5h. After the reaction is completed, liquid-solid separation is performed to obtain pure tellurium dioxide and neutralization tail liquid.

[0051] VIII: The obtained refined tellurium dioxide was added with distilled water at a liquid-to-solid ratio (L / kg) of 5:1 and stirred at 50°C for 30 minutes to separate the liquid and solid. The filter cake was dried and calcined in air at 600°C for 2 hours. The chemical purity of the final product tellurium dioxide met the TeO2 99.90 grade of "YS / T 1194-2017 Tellurium Dioxide" and the average particle size D50 was 63 microns.

Claims

1. A method for preparing high-purity tellurium dioxide powder by refining tellurium slag, characterized in that: The method for preparing high-purity tellurium dioxide powder by refining tellurium slag includes pre-treatment, main reaction and post-treatment steps, specifically including: A. Pre-treatment: 1) The tellurium slag to be treated is crushed to a particle size of -75 μm accounting for more than 90%, and water leaching liquid a and water leaching slag b are obtained through slurry mixing, water leaching and filtration, and the water leaching slag b is stored; 2) The water extract a is heated to 40-90°C, sodium sulfide and calcium chloride are added, and the mixture is stirred and reacted at a temperature of 40-90°C for 0.5-3h, and the impurity-removed liquid c and impurity-removed slag d are obtained by liquid-solid separation, and the impurity-removed slag d is stored; B. Main reaction: 1) Add EDTA to the impurity-removed liquid c, heat it to 40-100°C and stir it for 5-30 minutes, then slowly drop sulfuric acid solution at 40-100°C until the pH is 5-7, continue to stir the reaction at 40-100°C for 0.5-1h, and obtain crude tellurium dioxide e and neutralization tail liquid through liquid-solid separation, and the neutralization tail liquid enters wastewater treatment; 2) Add concentrated hydrochloric acid to the crude tellurium dioxide e, react at a temperature of 30-80°C for 10-60 minutes, and obtain a crude tellurium tetrachloride solution f and an insoluble slag through liquid-solid separation, and the insoluble slag is stored; 3) Add sodium sulfite to the crude tellurium tetrachloride solution f, stir and react for 0.5-1h, separate the liquid and solid to obtain metal tellurium powder g and neutralization tail liquid, and the neutralization tail liquid is used for wastewater treatment; 4) Add distilled water to the metal tellurium powder g to prepare a slurry, then add concentrated nitric acid and stir to react, and obtain tellurium dioxide h and oxidation tail liquid through liquid-solid separation, and the oxidation tail liquid is returned to step 1); 5) Add concentrated hydrochloric acid to tellurium dioxide h, react at a temperature of 30-80°C for 10-60 minutes, and obtain a refined tellurium tetrachloride solution i and an insoluble residue by liquid-solid separation. The insoluble residue is returned to step 4); C. Post-processing: 1) The refined tellurium tetrachloride solution i is heated to 35-90°C, and then ammonia water or sodium bicarbonate solution is added dropwise until the pH is 5-6, and the reaction is stirred for 0.4-0.6h. The refined tellurium dioxide j and the neutralization tail liquid are obtained by liquid-solid separation, and the neutralization tail liquid is sent to the wastewater treatment; 2) Add distilled water to the refined tellurium dioxide and stir and wash at a temperature of 40-60°C for 20-40 minutes. The filter cake is dried and calcined to obtain the target high-purity tellurium dioxide with an average particle size of 45-75 μm.

2. The method for preparing high-purity tellurium dioxide powder from refined tellurium slag according to claim 1, characterized in that: The refined tellurium slag is the tellurium slag obtained by pyrometallurgical smelting of copper anode mud and lead anode mud.

3. The method for preparing high-purity tellurium dioxide powder from refined tellurium slag according to claim 1, characterized in that: The water leaching described in step A 1) is carried out at a liquid-to-solid ratio of L / Kg (2-3):1 and a temperature of 50-100°C with stirring for 50-70 minutes.

4. The method for preparing high-purity tellurium dioxide powder from refined tellurium slag according to claim 1, characterized in that: In step A2), the amount of sodium sulfide added is 2-30 g / L; the amount of calcium chloride added is 0.5-20 g / L.

5. The method for preparing high-purity tellurium dioxide powder from refined tellurium slag according to claim 1, characterized in that: B. The amount of EDTA added in step 1) is 5-20 g / L; the mass percentage concentration of the sulfuric acid solution is 15-40%.

6. The method for preparing high-purity tellurium dioxide powder from refined tellurium slag according to claim 1, characterized in that: B. Adding distilled water to prepare the slurry and then adding concentrated nitric acid to stir the reaction as described in step 4) is to add distilled water to the metal tellurium powder g to prepare the slurry to a liquid-solid ratio of L / Kg of (1.5~2.5):1 and heat it to 15~90°C, then slowly add concentrated nitric acid while stirring until the black metal tellurium powder is no longer visible to the naked eye, and continue to stir the reaction for 0.5~1.5h.

7. The method for preparing high-purity tellurium dioxide powder from refined tellurium slag according to claim 1, characterized in that: C. The mass percentage concentration of the ammonia water described in step 1) is 10-28%.

8. The method for preparing high-purity tellurium dioxide powder from refined tellurium slag according to claim 1, characterized in that: C. The concentration of the sodium bicarbonate solution described in step 1) is 30-90 g / L.

9. The method for preparing high-purity tellurium dioxide powder from refined tellurium slag according to claim 1, characterized in that: C. The calcination in step 2) is carried out at 500-700°C in air.

10. The method for preparing high-purity tellurium dioxide powder from refined tellurium slag according to claim 1, characterized in that: C. The calcination time in step 2) is 1 to 3 hours.

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