Method for comprehensively enriching and recovering cadmium and thallium from complex arsenic sulfide slag

Abstract

The invention discloses a method for comprehensively enriching and recovering cadmium and thallium from complex arsenic sulfide slag, belongs to the technical field of harmless treatment of dangerous waste residues and resource recovery of rare and noble metals, and aims to solve the problems that the existing process is difficult to realize fractional separation of fluorine, chlorine, arsenic, cadmium and thallium in the arsenic sulfide slag, and the thallium is low in recovery rate and insufficient in purity. According to the method, fluorine and chlorine and thallium arsenic-cadmium lead are separated through graded alkaline leaching; the cadmium-containing lead slag is subjected to zinc electrodeposition waste liquid acid leaching and sodium sulfite and citric acid purification, and cadmium-containing coarse filtrate is obtained; adjusting the pH value of the thallium-containing arsenic liquid step by step, and adding sodium hydrosulfide for precipitation to obtain high-purity thallium slag; according to the method, no toxic gas is generated, the emission of wastewater is reduced by 80%, conventional equipment is used, industrialization is easy, and unification of harmlessness of hazardous waste and efficient recycling of resources is achieved.

Description

Technical Field

[0001] This invention belongs to the field of hazardous waste harmless treatment and rare and precious metal resource recovery technology, specifically a method for the comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag. Background Technology

[0002] With the large-scale development of non-ferrous metal smelting and chemical industries, a large amount of complex arsenic sulfide slag containing multiple components such as arsenic, cadmium, thallium, lead, fluorine, and chlorine has been generated. If it is directly piled up or landfilled without proper disposal, the heavy metals and arsenic in it will leach into water bodies and soil through rainwater and soil infiltration, causing groundwater pollution, excessive heavy metals in the soil, and other problems, threatening the ecosystem and human health.

[0003] Meanwhile, cadmium and thallium in arsenic sulfide slag are scarce and valuable metals. Cadmium is a key raw material for batteries and electronic components, while thallium is an important component of high-temperature superconducting materials and optical glass. If they are only disposed of in a harmless manner without being recycled, it will result in a serious waste of resources. The existing process uses a single pH adjustment and precipitant, which easily leads to the co-precipitation of thallium with arsenic and lead. The purity of thallium in the precipitate is less than 50%, making subsequent purification difficult and costly. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag. Addressing the problems of existing processes failing to achieve graded separation of fluorine, chlorine, arsenic, cadmium, and thallium in arsenic sulfide slag, and exhibiting low thallium recovery rates and insufficient purity, this invention separates fluorine and chlorine from thallium, arsenic, cadmium, and lead through graded alkaline leaching. The cadmium- and lead-containing slag is then purified by acid leaching with zinc electrowinning waste liquid and by adding sodium sulfite and citric acid to obtain a cadmium-containing coarse filtrate. The thallium- and arsenic-containing filtrate is then subjected to stepwise pH adjustment and precipitation with sodium hydrosulfide to obtain high-purity thallium slag. An aminated modified zeolite is prepared to adsorb cadmium, yielding a refined solution. Finally, metallic cadmium and thallium are recovered. The mother liquor is recycled for leaching, producing sodium sulfate as a byproduct. This invention generates no toxic gases, reduces wastewater discharge by 80%, uses conventional equipment, is easily industrialized, and achieves a unified approach to the harmless treatment of hazardous waste and efficient resource recovery.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for the comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag includes the following steps: Step 1: Add aminated modified zeolite to the cadmium-containing coarse filtrate, stir at 40-50℃ and 50-60r / min for 3-4h, and filter to obtain the cadmium-containing refined solution.

[0006] Step 2: The cadmium-containing refined liquid is sent to the zinc smelting system to recover metallic cadmium. The thallium slag is dissolved in 1 mol / L hydrochloric acid, precipitated with 10-12% oxalic acid, and roasted at 600-700℃ to obtain metallic thallium. After removing impurities, the liquid is evaporated and crystallized to recover sodium sulfate. The mother liquor is returned to alkaline leaching, thus completing the method for comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag.

[0007] Furthermore, the ratio of cadmium coarse filtrate to aminated modified zeolite is 40-42 L: 4-5 kg.

[0008] Furthermore, the specific preparation steps of the amination-modified zeolite are as follows: Zeolite, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water were added to a reaction vessel and stirred at 40-50℃ and 50-60 r / min for 3-4 h. After filtration, the filter cake was washed 2-4 times with deionized water and dried under vacuum at 60-70℃ for 1-2 h to obtain aminated modified zeolite.

[0009] Furthermore, the ratio of zeolite, γ-aminopropyltriethoxysilane, anhydrous ethanol, and deionized water is 5-6 kg: 800-900 mL: 8-9 L: 4-5 L.

[0010] Furthermore, the specific preparation steps for the cadmium-containing coarse filtrate are as follows: The cadmium-containing lead slag and zinc electrowinning waste liquid are mixed with dilute sulfuric acid and stirred at 50-60 r / min for 40-60 min at 40-50℃. Then sodium sulfite and citric acid are added, and stirring is continued for 70-80 min. Finally, 0.1 mol / L sulfuric acid is added to adjust the pH value to 3-4, and the mixture is filtered to obtain the cadmium-containing coarse filtrate.

[0011] Furthermore, the ratio of cadmium-containing lead slag, zinc electrowinning waste liquid, dilute sulfuric acid, sodium sulfite and citric acid is 80-100kg: 40-50L: 10-12L: 800-900g: 700-780g.

[0012] Furthermore, the specific preparation steps for thallium slag are as follows: Adjust the pH of the secondary filtrate containing thallium and arsenic to 8.8-9, then add sodium hydrosulfide and stir for 40-60 min at 40-50℃ and 50-60 r / min. Filter to remove arsenic residue, then adjust the pH to 6.8-7, add sodium hydrosulfide again, and continue stirring for 60-70 min. Filter to obtain thallium residue.

[0013] Furthermore, the ratio of thallium- and arsenic-containing secondary filtrate, sodium hydrosulfide, and sodium hydrosulfide is 80-90 kg: 0.8-0.9 kg: 1.2-1.4 kg.

[0014] Furthermore, the specific preparation steps for the thallium- and arsenic-containing secondary filtrate and cadmium- and lead-cadmium slag are as follows: Arsenic sulfide slag and a mixture of sodium hydroxide and sodium carbonate in a mass ratio of 2:1 were stirred and mixed. The liquid-to-solid ratio was 6:1 and the pH was 11.0. The mixture was leached at 20-25℃ and 50-60 r / min for 40-60 min. The filtrate was filtered to obtain a primary filtrate containing fluorine and chlorine. Then, the mixture was added again. The liquid-to-solid ratio was 8:1 and the pH was 12.5. The mixture was leached at 70-80℃ for 100-120 min. The filtrate was filtered to obtain a secondary filtrate containing thallium and arsenic and cadmium- and lead slag.

[0015] Furthermore, the mass ratio of arsenic sulfide slag to the mixture is 100-110:20-23.

[0016] Furthermore, arsenic sulfide slag contains 62-87% sulfur, 28.5-9% cadmium, 0.3-0.4% thallium, 1.2-1.4% arsenic, 0.8-1% fluorine and 1.5-1.7% chlorine.

[0017] The beneficial effects of this invention are: This invention uses conventional stirring, filtration, and adsorption equipment throughout the process, without the need for special high-end devices; the cadmium-containing refined liquid can be directly connected to the existing zinc smelting system, eliminating the need to build a new cadmium recovery production line; a single production line can process up to 50 tons / day, with strong process stability, making it suitable for large-scale applications.

[0018] The entire process is wet, generating no toxic gases. Wastewater discharge is reduced by 80% compared to existing processes. After targeted treatment, the waste residue achieves a 100% harmlessness rate, realizing the dual goals of harmless treatment of arsenic sulfide slag and resource utilization of cadmium and thallium. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: A method for the comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag, comprising the following steps: S1: Mix 100 kg of arsenic sulfide slag with 15 kg of a mixture of sodium hydroxide and sodium carbonate in a mass ratio of 2:1, with a liquid-to-solid ratio of 6:1 and pH=11.0. Leach at 20℃ and 50 r / min for 40 min. Filter to obtain a primary filtrate containing fluorine and chlorine. Then add another 5 kg of the mixture, with a liquid-to-solid ratio of 8:1 and pH=12.5. Leach at 70℃ for 100 min. Filter to obtain a secondary filtrate containing thallium and arsenic and cadmium- and lead slag.

[0021] The arsenic sulfide slag contains 62% sulfur, 28.5% cadmium, 0.3% thallium, 1.2% arsenic, 0.8% fluorine and 1.5% chlorine.

[0022] S2: Mix 80kg of cadmium-containing lead slag, 40L of zinc electrowinning waste liquid with 10L of dilute sulfuric acid, stir at 40℃ and 50r / min for 40min, then add 800g of sodium sulfite and 700g of citric acid, continue stirring for 70min, then add 0.1mol / L sulfuric acid to adjust the pH value to 3, and filter to obtain cadmium-containing coarse filtrate.

[0023] S3: Adjust the pH of 80 kg of secondary filtrate containing thallium and arsenic to 8.8, then add 0.8 kg of sodium hydrosulfide, stir at 40℃ and 50 r / min for 40 min, filter to remove arsenic residue, then adjust the pH to 6.8, add 1.2 kg of sodium hydrosulfide, continue stirring for 60 min, and filter to obtain thallium residue.

[0024] S4: Add 5 kg of zeolite, 800 mL of γ-aminopropyltriethoxysilane, 8 L of anhydrous ethanol and 4 L of deionized water to a reaction vessel, stir at 40 °C and 50 r / min for 3 h, filter, wash the filter cake twice with deionized water, and dry under vacuum at 60 °C for 1 h to obtain aminated modified zeolite.

[0025] S5: Add 4 kg of aminated modified zeolite to 40 L of cadmium-containing coarse filtrate, stir at 40 °C and 50 r / min for 3 h, and filter to obtain cadmium-containing refined solution; send the cadmium-containing refined solution to the zinc smelting system to recover metallic cadmium, dissolve the thallium slag in 1 mol / L hydrochloric acid, precipitate with 10% oxalic acid, and calcine at 600 °C to obtain metallic thallium, evaporate the liquid after impurity removal to recover sodium sulfate, and return the mother liquor to alkaline leaching, thus completing the method for comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag.

[0026] Example 2: A method for the comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag, comprising the following steps: S1: Mix 105 kg of arsenic sulfide slag and 16 kg of a mixture of sodium hydroxide and sodium carbonate in a mass ratio of 2:1, with a liquid-to-solid ratio of 6:1 and pH=11.0. Leach at 22.5℃ and 55 r / min for 50 min. Filter to obtain a primary filtrate containing fluorine and chlorine. Then add 5.5 kg of the mixture again, with a liquid-to-solid ratio of 8:1 and pH=12.5. Leach at 75℃ for 110 min. Filter to obtain a secondary filtrate containing thallium and arsenic and cadmium- and lead slag.

[0027] The arsenic sulfide slag contains 74.5% sulfur, 18.75% cadmium, 0.35% thallium, 1.3% arsenic, 0.9% fluorine and 1.6% chlorine.

[0028] S2: Mix 90kg of cadmium-containing lead slag, 45L of zinc electrowinning waste liquid with 11L of dilute sulfuric acid, stir at 45℃ and 55r / min for 50min, then add 850g of sodium sulfite and 740g of citric acid, continue stirring for 75min, then add 0.1mol / L sulfuric acid to adjust the pH to 3.5, and filter to obtain cadmium-containing coarse filtrate.

[0029] S3: Adjust the pH of 85 kg of secondary filtrate containing thallium and arsenic to 8.9, then add 0.85 kg of sodium hydrosulfide, stir at 45℃ and 55 r / min for 50 min, filter to remove arsenic residue, then adjust the pH to 6.9, add 1.3 kg of sodium hydrosulfide, continue stirring for 65 min, and filter to obtain thallium residue.

[0030] S4: Add 5.5 kg of zeolite, 850 mL of γ-aminopropyltriethoxysilane, 8.5 L of anhydrous ethanol and 4.5 L of deionized water to a reaction vessel, stir at 45 °C and 55 r / min for 3.5 h, filter, wash the filter cake three times with deionized water, and dry under vacuum at 65 °C for 1.5 h to obtain aminated modified zeolite.

[0031] S5: Add 4.5 kg of aminated modified zeolite to 41 L of cadmium-containing coarse filtrate, stir at 45 °C and 55 r / min for 3.5 h, filter to obtain cadmium-containing refined solution; send the cadmium-containing refined solution to the zinc smelting system to recover metallic cadmium, the thallium slag is dissolved in 1 mol / L hydrochloric acid, precipitated with 11% oxalic acid, and calcined at 650 °C to obtain metallic thallium, after impurity removal the liquid evaporates and crystallizes to recover sodium sulfate, the mother liquor is returned to alkaline leaching, thus completing the method of comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag.

[0032] Example 3: A method for the comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag, comprising the following steps: S1: Mix 110 kg of arsenic sulfide slag and 17 kg of a mixture of sodium hydroxide and sodium carbonate in a mass ratio of 2:1, with a liquid-to-solid ratio of 6:1 and pH=11.0. Leach at 25℃ and 60 r / min for 60 min. Filter to obtain a primary filtrate containing fluorine and chlorine. Then add another 6 kg of the mixture, with a liquid-to-solid ratio of 8:1 and pH=12.5. Leach at 80℃ for 120 min. Filter to obtain a secondary filtrate containing thallium and arsenic and cadmium- and lead slag.

[0033] The arsenic sulfide slag contains 87% sulfur, 9% cadmium, 0.4% thallium, 1.4% arsenic, 1% fluorine and 1.7% chlorine.

[0034] S2: Mix 100kg of cadmium-containing lead slag, 50L of zinc electrowinning waste liquid with 12L of dilute sulfuric acid, stir at 50℃ and 60r / min for 60min, then add 900g of sodium sulfite and 780g of citric acid, continue stirring for 80min, then add 0.1mol / L sulfuric acid to adjust the pH to 4, and filter to obtain cadmium-containing coarse filtrate.

[0035] S3: Adjust the pH of 90 kg of secondary filtrate containing thallium and arsenic to 9, then add 0.9 kg of sodium hydrosulfide, stir at 50℃ and 60 r / min for 60 min, filter to remove arsenic residue, adjust the pH to 7, add 1.4 kg of sodium hydrosulfide, continue stirring for 70 min, and filter to obtain thallium residue.

[0036] S4: Add 6 kg of zeolite, 900 mL of γ-aminopropyltriethoxysilane, 9 L of anhydrous ethanol and 5 L of deionized water to a reaction vessel, stir at 50 °C and 60 r / min for 4 h, filter, wash the filter cake with deionized water 4 times, and dry under vacuum at 70 °C for 2 h to obtain aminated modified zeolite.

[0037] S5: Add 5 kg of aminated modified zeolite to 42 L of cadmium-containing coarse filtrate, stir at 50 °C and 60 r / min for 4 h, and filter to obtain cadmium-containing refined solution; send the cadmium-containing refined solution to the zinc smelting system to recover metallic cadmium, dissolve the thallium slag in 1 mol / L hydrochloric acid, precipitate with 12% oxalic acid, and calcine at 700 °C to obtain metallic thallium, evaporate the liquid after impurity removal to recover sodium sulfate, and return the mother liquor to alkaline leaching, thus completing the method for comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide slag.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for comprehensive enrichment and recovery of cadmium and thallium from complex arsenic sulfide residues, characterized in that, It comprises the following steps: Step one: adding amino-modified zeolite to the cadmium-containing crude filtrate, stirring at 40-50℃ and 50-60r / min for 3-4h, and filtering to obtain cadmium-containing refined liquid; Step two: sending the cadmium-containing refined liquid to a zinc smelting system to recover metal cadmium, dissolving the thallium residue in 1mol / L hydrochloric acid, precipitating with 10-12% oxalic acid, roasting at 600-700℃ to obtain metal thallium, recovering sodium sulfate after impurity removal by evaporation crystallization, and returning the mother liquor to alkaline leaching to complete the method for comprehensive enrichment and recovery of cadmium and thallium from complex sulfide arsenic residue.

2. The method according to claim 1, wherein the method is characterized in that, The dosage ratio of the cadmium crude filtrate and the amino-modified zeolite is 40-42L:4-5kg.

3. The method according to claim 1, wherein the method is characterized in that, The specific preparation steps of the amino-modified zeolite are as follows: Add zeolite, γ-aminopropyl triethoxysilane, anhydrous ethanol and deionized water into a reaction kettle, stir at 40-50℃ and 50-60r / min for 3-4h, filter, wash the filter cake with deionized water for 2-4 times, and vacuum dry at 60-70℃ for 1-2h to obtain the amino-modified zeolite.

4. The method according to claim 3, wherein the method is characterized in that, The dosage ratio of the zeolite, γ-aminopropyl triethoxysilane, anhydrous ethanol and deionized water is 5-6kg:800-900mL:8-9L:4-5L.

5. The method according to claim 1, wherein the method is characterized in that, The specific preparation steps of the cadmium-containing crude filtrate are as follows: Mix cadmium-containing lead residue, zinc electrodeposition waste liquid and dilute sulfuric acid, stir at 40-50℃ and 50-60r / min for 40-60min, then add sodium sulfite and citric acid, continue to stir for 70-80min, add 0.1mol / L sulfuric acid to adjust the pH value to 3-4, and filter to obtain the cadmium-containing crude filtrate.

6. The method according to claim 5, wherein the method is characterized in that, The dosage ratio of the cadmium-containing lead residue, zinc electrodeposition waste liquid, dilute sulfuric acid, sodium sulfite and citric acid is 80-100kg:40-50L:10-12L:800-900g:700-780g.

7. The method according to claim 1, wherein the method is characterized in that, The specific preparation steps of the thallium residue are as follows: Adjust the pH value of the thallium and arsenic secondary filtrate to 8.8-9, then add sodium hydrosulfide, stir at 40-50℃ and 50-60r / min for 40-60min, filter out the arsenic residue, adjust the pH value to 6.8-7 again, add sodium hydrosulfide, continue to stir for 60-70min, and filter to obtain the thallium residue.

8. The method according to claim 7, wherein the method is characterized in that, The dosage ratio of the thallium and arsenic secondary filtrate, sodium hydrosulfide and sodium hydrosulfide is 80-90kg:0.8-0.9kg:1.2-1.4kg.

9. The method according to claim 5, wherein the method is characterized in that, The specific preparation steps of the thallium and arsenic secondary filtrate and cadmium lead residue are as follows: Mix sulfide arsenic residue and a mixture of sodium hydroxide and sodium carbonate with a mass ratio of 2:1, stir and mix, liquid-solid ratio 6:1, pH=11.0, leach at 20-25℃ and 50-60r / min for 40-60min, filter to obtain the primary filtrate containing fluorine and chlorine, then add the mixture again, liquid-solid ratio 8:1, pH=12.5, leach at 70-80℃ for 100-120min, and filter to obtain the secondary filtrate containing thallium and arsenic and cadmium-containing lead residue; The mass ratio of the sulfide arsenic residue and the mixture is 100-110:20-23.

10. The method according to claim 9, wherein the method is characterized in that, The arsenic sulphide slag contains 62-87% sulphur, 28.5-9% cadmium, 0.3-0.4% thallium, 1.2-1.4% arsenic, 0.8-1% fluorine and 1.5-1.7% chlorine.