Method for preparing high-purity tellurium dioxide by removing selenium from material containing selenium and tellurium

Abstract

The invention provides a method for preparing high-purity tellurium dioxide by removing selenium from a material containing selenium and tellurium, which comprises the following specific steps: S1, crushing tellurium slag produced from lead anode slime containing Na2TeO3, carrying out alkaline leaching on the obtained filtrate, purifying the obtained filtrate, adding sodium sulfide to remove impurity lead, carrying out filter pressing, and neutralizing the obtained filtrate to obtain crude tellurium dioxide; s2, the crude tellurium dioxide is put into an acid leaching tank, deionized water and hydrochloric acid are sequentially added, an acid dissolution reaction is carried out, and a mixed solution is obtained; s3, sodium chlorate is added into the mixed solution to adjust the potential to 600-900 mV, sodium sulfite is added for a reaction until Se in the mixed solution is lower than 50 mg / L, filter pressing is conducted, and filtrate is obtained; and S4, adding the filtrate into caustic soda flakes to obtain tellurium dioxide. The method disclosed by the invention is beneficial to improving the efficiency of subsequently removing Se by sodium sulfite, avoiding the loss of tellurium, providing a basis for high current of subsequent electrodeposition, greatly improving the electrodeposition efficiency, shortening the production period, remarkably improving the yield and quality of tellurium ingot products, reducing the production cost and having good process stability.

Description

Technical Field

[0001] The invention relates to the technical field of tellurium electrodeposition refining, and in particular to a method for preparing high-purity tellurium dioxide by removing selenium from selenium-tellurium-containing materials. Background Art

[0002] The production process of national standard tellurium ingots is to use sodium tellurite solution for electrolysis to obtain crude tellurium and then refine it to obtain national standard tellurium ingots. Sodium tellurite solution is made by the reaction of tellurium dioxide and sodium hydroxide solution. In order to obtain qualified sodium tellurite solution, qualified tellurium dioxide is required.

[0003] Tellurium is a rare metal with a wide range of applications in the industrial field. Tellurium is generally recovered from copper smelting anode mud. The recovery process is mainly alkaline leaching. After the leachate is purified and neutralized, the electrolyte is prepared for insoluble anode electrolysis. During the tellurium electrolytic refining process, some impurities in the tellurium-containing materials, such as selenium, follow the chemical dissolution of alkaline leaching and enter the alkaline leaching solution. As production proceeds, selenium in the alkaline leaching solution continues to be enriched, and it is difficult to separate from tellurium dioxide during the hydrolysis process, so it enters the electrolytic solution, which brings higher selenium impurities to the production of tellurium and affects the quality of tellurium.

[0004] In order to make the impurity content of the tellurium product less than the lower limit, the alkaline leaching solution must be deselenized and impurized to ensure the normal operation of the electrolytic process. In the prior art, the traditional process flow of preparing tellurium dioxide by alkaline leaching and deselenization of selenium-containing tellurium materials is: selenium-containing tellurium materials → alkaline leaching and tellurium separation → hydrolysis and precipitation of tellurium → calcination and deselenization → tellurium dioxide. That is, by utilizing the principle of the low boiling point of selenium dioxide, selenium dioxide is volatilized by calcination in a calcining furnace to purify tellurium dioxide. However, this process not only causes tellurium loss during the calcination process, but also has unsatisfactory selenium removal efficiency, resulting in high processing costs and affecting the competitiveness of enterprises. Summary of the invention

[0005] In view of this, the present invention proposes a method for removing selenium from selenium-tellurium-containing materials to prepare high-purity tellurium dioxide.

[0006] The technical solution of the present invention is achieved in this way:

[0007] A method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide, the specific steps comprising:

[0008] S1. The tellurium slag produced by the lead anode mud containing Na2TeO3 is crushed, and the filtrate after alkaline leaching enters the purification process, sodium sulfide is added to remove the impurity lead, and the filter is pressed and the filtrate is neutralized to obtain crude tellurium dioxide;

[0009] S2, putting the crude tellurium dioxide into an acid leaching tank, adding deionized water and hydrochloric acid in sequence, performing an acid dissolution reaction, and obtaining a mixed solution;

[0010] The mass ratio of the crude tellurium dioxide to deionized water and hydrochloric acid is 1:1-3:3-5;

[0011] S3, adding sodium chlorate to the mixed solution to adjust the potential to 600-900 mV, then adding sodium sulfite to react, filter pressing, and obtain a filtrate;

[0012] S4. Add caustic soda flakes to the filtrate of S3 to obtain the target tellurium dioxide product.

[0013] Furthermore, in step S1, the amount of sodium sulfide added is 0.5-5 times the lead content in the filtrate.

[0014] Furthermore, in step S2, the concentration of the hydrochloric acid is 1-10 mol / L.

[0015] Furthermore, in step S2, the temperature of the acid dissolution reaction is 60-80°C and the time is 0.5-5h.

[0016] Furthermore, in step S3, the amount of sodium sulfite added is 3-5 times the selenium content in the mixed solution.

[0017] Furthermore, in step S3, the reaction is terminated until the Se in the mixed solution is less than 50 mg / L.

[0018] Furthermore, in step S4, the addition of caustic soda is to adjust the pH of the system to 5.0-6.5.

[0019] Furthermore, the obtained tellurium dioxide product is used for the subsequent preparation of high-quality tellurium ingots.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention treats crude tellurium dioxide by a chemical reaction method with a limited amount of acid solution added and an adjusted potential, which is beneficial to improving the efficiency of subsequent Se removal by sodium sulfite, avoiding the loss of tellurium in the traditional calcination and selenium removal process, providing a basis for the subsequent large current of electrolysis, greatly improving the electrolysis efficiency, shortening the production cycle, significantly improving the output and quality of tellurium ingot products, reducing production costs, and improving process stability.

[0022] 2. The tellurium recovery rate of the tellurium dioxide product obtained by the method of the present invention is as high as 99%, the content of impurity selenium is less than 0.01%, and the purity of the tellurium ingot prepared by subsequent liquid making, electrodeposition and casting reaches more than 99.99%. DETAILED DESCRIPTION

[0023] In order to better understand the technical content of the present invention, specific embodiments are provided below to further illustrate the present invention.

[0024] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods.

[0025] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0026] A method for preparing high-purity tellurium dioxide by removing selenium from selenium-tellurium-containing materials. The main components of the selenium-tellurium-containing materials are Na2TeO3 and soluble selenium and other impurity components. Generally, the content of Na2TeO3 in the selenium-tellurium-containing materials is 15-25%, and the content of selenium is 1-5%.

[0027] Example 1

[0028] S1. Crush 600 g of tellurium slag, see Table 1 for specific ingredients, mix the crushed tellurium slag with 1200 mL of alkali solution to form a filtrate, add sodium sulfide to the filtrate, the amount of sodium sulfide added is 0.5 times the lead content in the filtrate, remove impurity lead, filter press, neutralize the filtrate, and obtain crude tellurium dioxide;

[0029] Table 1

[0030] Element Te Bi Cu Sb pb Se content 22.56％ 9.72％ 1.12％ 6.06％ 10.55％ 2.90％

[0031] S2. Put the crude tellurium dioxide into an acid leaching tank, add deionized water and 10 mol / L hydrochloric acid in sequence, the mass ratio of crude tellurium dioxide to deionized water and hydrochloric acid is 1:2:4, and carry out acid dissolution reaction at 70°C for 1 hour to obtain a mixed solution;

[0032] S3, adding sodium chlorate to the mixed solution to adjust the potential to 800 mV, then adding sodium sulfite, the amount of sodium sulfite added is 4 times the selenium content in the mixed solution, reacting until Se in the mixed solution is less than 50 mg / L, and filtering to obtain a filtrate;

[0033] S4. Add caustic soda flakes to the filtrate of S3 and adjust the pH of the system to 5.5±0.1 to obtain the target tellurium dioxide product, the composition of which is shown in Table 2.

[0034] Table 2

[0035] Element Te Bi Cu Sb pb Se content 72.5200％ 0.0011％ 0.0070％ 0.0010％ 0.0120％ 0.0094％

[0036] Example 2

[0037] S1. Crush 600 g of tellurium slag, see Table 3 for specific ingredients, mix the crushed tellurium slag with 900 mL of alkali solution to form a filtrate, add sodium sulfide to the filtrate, the amount of sodium sulfide added is 1.5 times the lead content in the filtrate, remove impurity lead, filter press, neutralize the filtrate, and obtain crude tellurium dioxide;

[0038] Table 3

[0039] Element Te Bi Cu Sb pb Se content 18.65％ 10.48％ 1.94％ 4.95％ 11.85％ 3.60％

[0040] S2. Put the crude tellurium dioxide into an acid leaching tank, add deionized water and 5 mol / L hydrochloric acid in sequence, the mass ratio of crude tellurium dioxide to deionized water and hydrochloric acid is 1:1:3, and carry out acid dissolution reaction at 60°C for 2h to obtain a mixed solution;

[0041] S3, adding sodium chlorate to the mixed solution to adjust the potential to 600 mV, then adding sodium sulfite, the amount of sodium sulfite added is 3 times the selenium content in the mixed solution, reacting until Se in the mixed solution is less than 50 mg / L, and filtering to obtain a filtrate;

[0042] S4. Add caustic soda flakes to the filtrate of S3 and adjust the pH of the system to 5.1±0.1 to obtain the target tellurium dioxide product, the composition of which is shown in Table 4.

[0043] Table 4

[0044] Element Te Bi Cu Sb pb Se content 71.9900％ 0.0025％ 0.0033％ 0.0005％ 0.0130％ 0.0082％

[0045] Example 3

[0046] S1. 600 g of tellurium slag was crushed, and the specific composition was shown in Table 5. The crushed tellurium slag was mixed with 1800 mL of alkali solution to form a filtrate. Sodium sulfide was added to the filtrate, and the amount of sodium sulfide added was 2.5 times the lead content in the filtrate. Impurity lead was removed, and filter pressing was performed. The filtrate was neutralized to obtain crude tellurium dioxide;

[0047] Table 5

[0048] Element Te Bi Cu Sb Pb Se content 21.31％ 12.72％ 2.32％ 3.86％ 7.79％ 4.70％

[0049] S2, putting the crude tellurium dioxide into an acid leaching tank, adding deionized water and 2 mol / L hydrochloric acid in sequence, the mass ratio of crude tellurium dioxide to deionized water and hydrochloric acid being 1:3:5, performing acid dissolution reaction at 80°C for 4 hours to obtain a mixed solution;

[0050] S3, adding sodium chlorate to the mixed solution to adjust the potential to 900 mV, then adding sodium sulfite, the amount of sodium sulfite added is 5 times the selenium content in the mixed solution, reacting until Se in the mixed solution is less than 50 mg / L, and filtering to obtain a filtrate;

[0051] S4. Add caustic soda flakes to the filtrate of S3 and adjust the pH of the system to 6.4±0.1 to obtain the target tellurium dioxide product, the composition of which is shown in Table 6.

[0052] Table 6

[0053] Element Te Bi Cu Sb Pb Se content 75.0100％ 0.0036％ 0.0054％ 0.0008％ 0.0090％ 0.0081％

[0054] It can be seen from Examples 1 to 3 that the tellurium dioxide obtained by the preparation method of the present invention has a selenium impurity content of less than 0.01%. From crude tellurium dioxide to pure tellurium dioxide, the tellurium recovery rate can reach 99%.

[0055] Example 4

[0056] The tellurium dioxide prepared in Example 1-3 was dissolved in alkali solution and purified with sodium sulfide before being injected into an electrolytic cell. The electrolytically produced tellurium sheets were washed, dried, melted, and cast to obtain high-quality tellurium ingots. The purity results are shown in Table 7.

[0057] Table 7

[0058] sample Tellurium Ingot Purity Example 1 99.9947％ Example 2 99.9933％ Example 3 99.9959％

[0059] It can be seen from Table 7 that the high-purity tellurium dioxide prepared by removing selenium from selenium-tellurium-containing materials of the present invention is subsequently used to prepare tellurium ingots, and the purity reaches more than 99.99%.

[0060] Comparative Example 1

[0061] The conventional process of preparing tellurium dioxide by alkali leaching of selenium-containing tellurium materials to remove selenium is as follows: selenium-containing tellurium materials → alkali leaching to separate tellurium → hydrolysis to precipitate tellurium → calcination to remove selenium → tellurium dioxide.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that the potential is not adjusted, and the rest is the same as Example 1.

[0064] S1. Crush 600 g of tellurium slag, mix the crushed tellurium slag with 1200 mL of alkali solution to form a filtrate, add sodium sulfide to the filtrate, the amount of sodium sulfide added is 0.5 times the lead content in the filtrate, remove the lead impurity, filter press, and neutralize the filtrate to obtain crude tellurium dioxide;

[0065] S2. Put the crude tellurium dioxide into an acid leaching tank, add deionized water and 10 mol / L hydrochloric acid in sequence, the mass ratio of crude tellurium dioxide to deionized water and hydrochloric acid is 1:2:4, and carry out acid dissolution reaction at 70° C. for 1 hour to obtain a mixed solution;

[0066] S3, adding sodium sulfite to the mixed solution, wherein the amount of sodium sulfite added is 4 times the selenium content in the mixed solution, reacting until Se in the mixed solution is less than 50 mg / L, and filtering to obtain a filtrate;

[0067] S4. Add caustic soda flakes to the filtrate of S3 and adjust the pH of the system to 5.5±0.1 to obtain tellurium dioxide product.

[0068] Comparative Example 3

[0069] Tellurium dioxide is prepared by the method of CN109775670A.

[0070] That is, a method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide, the specific steps comprising:

[0071] S1. Pretreatment: 600 g of tellurium slag was crushed, 1800 mL of deionized water was added, and the mixture was stirred to form a slurry. Sodium sulfite was added in an amount of 4 times the selenium content in the slurry to carry out a reaction;

[0072] S2. Acidification selenium precipitation: After the reaction is completed, a catalyst consisting of sodium chloride and sulfuric acid in a mass ratio of 1:2 is added to catalyze tellurium precipitation. The amount of chloride ions added is 1% of the mass of the tellurium slag. Sulfuric acid is added to adjust the pH of the solution to 1.5. The reaction is carried out at 75°C for 1 hour to obtain a selenium precipitation slurry.

[0073] S3, alkali leaching to separate tellurium: add sodium hydroxide according to 1.3 times the tellurium content in the selenium precipitation slurry, control the temperature at 55°C when adding alkali, raise the temperature to 90°C after adding alkali, react for 1 hour, filter, and obtain high-selenium slag and alkali leaching liquid;

[0074] S4. Selenium removal by hydrolysis: add sulfuric acid to the alkaline leaching solution for hydrolysis. The acid concentration is controlled at 50% and the hydrolysis temperature is 75°C. Stir well and measure the pH value intermittently until it stabilizes at pH 4. Filter to obtain tellurium dioxide product.

[0075] The tellurium dioxide products obtained by the methods of Example 1 and Comparative Example 1 were analyzed, and the results are shown in Table 8.

[0076] Table 8

[0077] Tellurium recovery rate Selenium content Tellurium Ingot Purity Example 1 99％ 0.0094％ 99.9947％ Comparative Example 1 96％ 0.2077％ 99.0165％ Comparative Example 2 97％ 0.1214％ 99.4747％ Comparative Example 3 98％ 0.0958％ 99.1654％

[0078] It can be seen from Table 8 that the tellurium dioxide obtained by the method of the present invention has a high tellurium recovery rate and a high selenium removal efficiency, and the purity of the prepared tellurium ingot reaches 99.9947%.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide, characterized in that: The specific steps include: S1. The tellurium slag produced by the lead anode mud containing Na2TeO3 is crushed, and the filtrate after alkaline leaching enters the purification process, sodium sulfide is added to remove the impurity lead, and the filter is pressed and the filtrate is neutralized to obtain crude tellurium dioxide; S2, putting the crude tellurium dioxide into an acid leaching tank, adding deionized water and hydrochloric acid in sequence, performing an acid dissolution reaction, and obtaining a mixed solution; The mass ratio of the crude tellurium dioxide to deionized water and hydrochloric acid is 1:1-3:3-5; S3, adding sodium chlorate to the mixed solution to adjust the potential to 600-900 mV, then adding sodium sulfite to react, filter pressing, and obtain a filtrate; S4. Add caustic soda flakes to the filtrate of S3 to obtain the target tellurium dioxide product.

2. A method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide as claimed in claim 1, characterized in that: In step S1, the amount of sodium sulfide added is 0.5-5 times the lead content in the filtrate.

3. A method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide as claimed in claim 1, characterized in that: In step S2, the concentration of the hydrochloric acid is 1-10 mol / L.

4. A method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide as claimed in claim 1, characterized in that: In step S2, the temperature of the acid dissolution reaction is 60-80°C and the time is 0.5-5h.

5. A method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide as claimed in claim 1, characterized in that: In step S3, the amount of sodium sulfite added is 3-5 times the selenium content in the mixed solution.

6. A method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide as claimed in claim 1, characterized in that: In step S3, the reaction is completed until the Se in the mixed solution is less than 50 mg / L.

7. A method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide as claimed in claim 1, characterized in that: In step S4, the addition of caustic soda flakes is to adjust the pH of the system to 5.0-6.

5.

8. A method for removing selenium from a material containing selenium and tellurium to prepare high-purity tellurium dioxide as claimed in claim 1, characterized in that: The obtained tellurium dioxide product is used for the subsequent preparation of high-quality tellurium ingots.