Method for deeply removing arsenic from nickel sulfate solution

Abstract

The invention discloses a method for deeply removing arsenic from a nickel sulfate solution, which comprises the following steps: adjusting the pH value by using nickel hydroxide to form colloid to preliminarily remove arsenic, oxidizing by using sodium sulfate, and adding polyferric sulfate to form ferric hydroxide colloid to deeply adsorb and remove arsenic, and is simple in process, convenient to implement in the production process, capable of greatly reducing the cost and reducing the environmental pollution, and suitable for industrial production. The method comprises the following steps: adjusting the pH value of a low-pH leaching solution / anolyte / crude nickel sulfate dissolving solution to 4.0 or more by using nickel hydroxide, carrying out filter pressing to remove slag, adding arsenic ions in a sodium persulfate oxidation solution, reacting for 30 minutes, adding polyferric sulfate, reacting for 30 minutes, and carrying out filter pressing to obtain a nickel sulfate solution which is almost free of arsenic, and the method is efficient, safe and environment-friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrometallurgy, and particularly relates to a method for deeply removing arsenic from nickel sulfate solution. Background Art

[0002] Arsenic is one of the very common metal impurities in the industrial production field, which not only affects the extraction and recovery of other metals, but also affects the treatment and discharge of wastewater. Therefore, the arsenic removal process for arsenic-containing nickel sulfate solution has received extensive attention. At present, in the methods used for arsenic removal from nickel sulfate solution, the added Fe element is not fully utilized, resulting in waste of iron element. In this patent, the arsenic removal slag is recycled to make full use of the iron element in the solution as much as possible under the condition of ensuring the arsenic removal requirement, and reduce the emission of solid waste.

[0003] At present, downstream customers of our company use nickel sulfate solution for electrowinning nickel products, and the content of arsenic has a great impact on the product quality of electrowinning nickel products. Therefore, arsenic removal from nickel sulfate solution is an urgent problem to be solved. In order to improve the quality of nickel sulfate solution and reduce environmental pollution, it is particularly important to deeply remove arsenic from nickel sulfate solution. Summary of the Invention

[0004] I. Technical Problem to be Solved: Nickel sulfate solution is used for electrowinning nickel products, and the content of arsenic has a great impact on the product quality of electrowinning nickel products. Therefore, a method for deeply removing arsenic from nickel sulfate solution is needed.

[0005] II. The technical solution adopted by the present invention is as follows: A method for deeply removing arsenic from nickel sulfate solution, comprising the following steps: (1) Adjust the pH of the low-pH nickel sulfate solution (including leaching solution, anode solution or crude nickel sulfate dissolution solution) in the leaching autoclave using nickel hydroxide, and adjust the pH to above 4.0; (2) Filter the solution in step (1), the solution enters the next process, add sodium persulfate for oxidation, control the temperature at 60 - 80 °C, and the reaction time is above 30 min; (3) Add polyferric sulfate to the solution in step (2) to continue the reaction. If the pH decreases, add nickel hydroxide to adjust the pH to above 4.0; the reaction time is above 30 min; (4) Filter the solution in step (3) to obtain low-arsenic nickel sulfate solution and the filter residue after filtration; When arsenic removal from the nickel sulfate solution is carried out again, the filter residue in step (4) is used to replace the polyferric sulfate in step (3) to continue the reaction. The filter residue in step (4) is periodically discharged, and the arsenic-containing waste residue is periodically cleaned. When the depth of arsenic removal cannot reach 0.0003 g / L after the addition of sodium persulfate, the arsenic-containing waste residue is cleaned to ensure that the depth of arsenic removal from the nickel sulfate solution remains below 0.0003 g / L.

[0006] Furthermore, the technical solution lies in that the addition amount of sodium persulfate in step (2) is such that the mass ratio of the solution to sodium persulfate is 5000:1.

[0007] Furthermore, the technical solution lies in that the addition amount of polyferric sulfate in step (3) is such that the mass ratio of the solution to polyferric sulfate is 1000:1.

[0008] Furthermore, the technical solution lies in that the arsenic content in the low-arsenic solution in step (4) is below 0.0003 g / L.

[0009] The reaction mechanism is as follows: 1. Adding sodium persulfate to oxidize trivalent arsenic to pentavalent arsenic S2O8 2+ +AsO3 3- =AsO4 3- +2SO4 2+ 2. The pentavalent AsO4 in the solution 3- forms an iron arsenate precipitate with F e3+ ions Fe3++AsO4 3- =FeAsO4 3- ↓ 3. When the pH is adjusted to above 4.0, a large amount of Fe(OH)3 colloid will form in the solution, and the formed colloid will strongly adsorb H3AsO4 in the solution, resulting in a large amount of arsenic removal.

[0010] III. Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: The process of initially removing arsenic by forming a colloid after adjusting the pH value with nickel hydroxide, then oxidizing with sodium persulfate and adding polyferric sulfate to form a ferric hydroxide colloid for deep adsorption and arsenic removal has a simple process, is convenient to implement during the production process, can greatly reduce costs, and reduce environmental pollution.

[0011] Adjust the pH of the leaching solution / anolyte / crude nickel sulfate solution with low pH to 4.0 or higher using nickel hydroxide. After filtering to remove slag, add sodium persulfate to oxidize the arsenic ions in the solution. After reacting for 30 min, add polyferric sulfate and react for another 30 min, then filter to obtain a nickel sulfate solution with almost no arsenic (arsenic content below 0.0003 g / L), achieving deep arsenic removal. The present invention is efficient, safe, and environmentally friendly.

[0012] In the present invention, the arsenic removal slag can be reused multiple times to reduce the usage amount of polyferric sulfate added. At the same time, since relatively less iron element is added, while ensuring that the arsenic element meets the standard, it will not significantly affect the filtration rate. Detailed implementation manners

[0013] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further details the present invention in combination with embodiments.

[0014] Example 1 Take 500 g of crude nickel sulfate and dissolve it in 1000 mL of pure water to prepare a nickel sulfate solution with a Ni ion concentration of 100 g / L or higher. Take 1000 mL of the solution and place it in a beaker. The pH of the nickel sulfate solution is 1.5. Adjust the pH to 4.0 or higher using nickel hydroxide, and filter to obtain a preliminarily arsenic-removed nickel sulfate solution. Place the beaker containing the nickel sulfate solution in a water bath and heat it to 60 °C. Add 0.2 g of sodium persulfate. After reacting for 30 min, add 1 g of polyferric sulfate and continue to react for 30 min, then filter to obtain an arsenic-removed nickel sulfate solution and send it for sample analysis. Reuse the filter residue added with polyferric sulfate solution. The previous steps are the same as the above steps. In the nickel sulfate solution after adding sodium persulfate, add the filter residue (without adding polyferric sulfate) and continue to react for 30 min, then filter to obtain an arsenic-removed solution and send it for sample analysis.

[0015] Arsenic content of the nickel sulfate solution after dissolving crude nickel sulfate: 0.11 g / L; arsenic content of the nickel sulfate solution after adjusting the pH with nickel hydroxide: 0.0012 g / L, arsenic content of the arsenic-removed nickel sulfate solution: 0.0001 g / L. Arsenic content of the arsenic-removed solution after reusing the filter residue: 0.0001 g / L.

[0016] Example 2 This embodiment provides a method for removing arsenic and antimony from nickel sulfate solution by controlling the redox potential. The difference lies in: Take 500 g of crude nickel sulfate and dissolve it in 1000 mL of pure water to prepare a nickel sulfate solution with a nickel ion concentration of more than 100 g / L. Take 1000 mL of this solution and place it in a beaker. The pH of the nickel sulfate solution is 1.5. Adjust the pH to above 4.0 with nickel hydroxide, and then perform suction filtration to obtain a nickel sulfate solution with preliminary arsenic removal. Place the beaker containing the nickel sulfate solution in a water bath and heat it to 80 °C. Add 0.2 g of sodium persulfate. After reacting for 30 min, add 1 g of polyferric sulfate and continue to react for 30 min. Then filter to obtain a nickel sulfate solution after arsenic removal and send it for sample analysis. Reuse the filter residue added with the polyferric sulfate solution. The previous steps are the same as the above steps. In the nickel sulfate solution after adding sodium persulfate, add the filter residue (without adding polyferric sulfate), continue to react for 30 min, perform suction filtration to obtain the solution after arsenic removal, and send it for sample analysis.

[0017] Arsenic content in the nickel sulfate solution after dissolving crude nickel sulfate: 0.086 g / L; arsenic content in the nickel sulfate solution after adjusting the pH with nickel hydroxide: 0.0009 g / L, arsenic content in the nickel sulfate solution after arsenic removal: 0.0001 g / L. Arsenic content in the solution after arsenic removal after reusing the filter residue: 0.0001 g / L.

[0018] Example 3 This example provides a method for removing arsenic and antimony from nickel sulfate solution by controlling the redox potential. The difference is as follows: Take 500 g of crude nickel sulfate and dissolve it in 1000 mL of pure water to prepare a nickel sulfate solution with a nickel ion concentration of more than 100 g / L. Take 1000 mL of this solution and place it in a beaker. The pH of the nickel sulfate solution is 1.5. Adjust the pH to above 4.0 with nickel hydroxide, and then perform suction filtration to obtain a nickel sulfate solution with preliminary arsenic removal. Place the beaker containing the nickel sulfate solution in a water bath and heat it to 80 °C. Add 0.2 g of sodium persulfate. After reacting for 30 min, add the filter residue in Example 2 and continue to react for 30 min. Then filter to obtain a nickel sulfate solution after arsenic removal and send it for sample analysis. Reuse the filter residue added with the polyferric sulfate solution. The previous steps are the same as the above steps. In the nickel sulfate solution after adding sodium persulfate, add the filter residue (without adding polyferric sulfate), continue to react for 30 min, perform suction filtration to obtain the solution after arsenic removal, and send it for sample analysis.

[0019] Arsenic content in the nickel sulfate solution after dissolving crude nickel sulfate: 0.24 g / L; arsenic content in the nickel sulfate solution after adjusting the pH with nickel hydroxide: 0.0010 g / L, arsenic content in the nickel sulfate solution after arsenic removal: 0.0001 g / L.

[0020] Comparative Example 1 This comparative example uses the method in Example 1, with the difference that the pH value is adjusted to 3.7. Specifically, the arsenic content in the nickel sulfate solution after dissolving crude nickel sulfate is 0.17 g / L; the arsenic content in the nickel sulfate solution after adjusting the pH with nickel hydroxide is 0.0045 g / L; and the arsenic content in the nickel sulfate solution after arsenic removal is 0.0013 g / L. It shows that when the pH value is lower than 4.0, the purpose of deep arsenic removal cannot be achieved.

[0021] Comparative Example 2 This comparative example uses the method in Example 1, with the difference that the reaction temperature is controlled at 40°C. Specifically, the arsenic content in the nickel sulfate solution after dissolving crude nickel sulfate is 0.11 g / L; the arsenic content in the nickel sulfate solution after adjusting the pH with nickel hydroxide is 0.0032 g / L; and the arsenic content in the nickel sulfate solution after arsenic removal is 0.0009 g / L. The purpose of deep arsenic removal cannot be achieved.

[0022] The above are only the preferred embodiments of the present invention.

Claims

1. A method for deep removal of arsenic from nickel sulfate solution, characterized in that, It includes the following steps: (1) Adjust the pH of the nickel sulfate solution with low pH in the leaching kettle (including leaching solution, anode solution or crude nickel sulfate dissolution solution) using nickel hydroxide, and adjust the pH to above 4.0; (2) Filter the solution in step (1), the solution enters the next process, add sodium persulfate for oxidation, control the temperature at 60-80 °C, and the reaction time is more than 30 min; (3) Add polyferric sulfate to the solution in step (2) to continue the reaction. If the pH decreases, add nickel hydroxide to adjust the pH to above 4.0; the reaction time is more than 30 min; (4) Filter the solution in step (3) to obtain a nickel sulfate solution with low arsenic and the filter residue after filtration; (5) When arsenic removal of the nickel sulfate solution is carried out again, use the filter residue in step (4) to replace the polyferric sulfate in step (3) to continue the reaction.

2. The method for deep arsenic removal from nickel sulfate solution according to claim 1, characterized in that, The addition amount of sodium persulfate in step (2) is that the mass ratio of the solution to sodium persulfate is 5000:

1.

3. A method for deep arsenic removal from nickel sulfate solution according to claim 1, characterized in that, The addition amount of polyferric sulfate in step (3) is that the mass ratio of the solution to polyferric sulfate is 1000:

1.

4. A method for deeply removing arsenic from nickel sulfate solution according to claim 1, characterized in that, The arsenic content in the low-arsenic solution in step (4) is below 0.0003 g / L.

5. A method for deeply removing arsenic from a nickel sulfate solution according to claim 1, characterized in that, The filter residue in step (4) is periodically opened, and the arsenic-containing waste residue is regularly cleaned. When the arsenic removal depth cannot reach 0.0003 g / L after adding sodium persulfate, clean the arsenic-containing waste residue to ensure that the arsenic removal depth of the nickel sulfate solution remains below 0.0003 g / L.