Method for producing high-purity nickel surface
Provided is a production method for obtaining high purity nickel sulfate having low levels of impurities, particularly low levels of magnesium and chloride, by adjusting the concentration of an extractant and the pH concentration at the time of treatment in a process of obtaining a nickel sulfate solution having a high nickel concentration by solvent extraction using an acidic organic extractant.
1. A method for producing high purity nickel sulfate, comprising
performing a sulfurization step by adding a sulfurizing agent to an acidic solution containing nickel, and obtaining a precipitate of nickel sulfide and a solution;
performing a redissolution step by preparing a slurry of the nickel sulfide and adding an oxidizing agent to the slurry, to obtain a concentrated solution of nickel;
performing a solution purification step by subjecting the concentrated solution of nickel to neutralization by adding a neutralizing agent, and thereby obtaining a neutralized precipitate and a concentrated solution of nickel after iron removal thus produced; and
performing a solvent extraction step by subjecting the concentrated solution of nickel after iron removal to solvent extraction, and thereby obtaining a stripped liquid and a nickel sulfate solution.
2. The method for producing high purity nickel sulfate of claim 1 , wherein the redissolution step of (2) is carried out at a temperature in the range of from 60° C. to 180° C.
3. The method for producing high purity nickel sulfate of claim 1 , wherein the oxidizing agent that is added in the redissolution step of (2) is at least one oxidizing agent selected from air, oxygen, a hydrogen peroxide solution, and ozone gas.
4. The method for producing high purity nickel sulfate of claim 1 , wherein the neutralization in the solution purification step of (3) is carried out by adding an alkali as a neutralizing agent and thereby adjusting the pH to the range of from 5.0 to 6.0.
5. The method for producing high purity nickel sulfate of claim 1 , wherein the solvent extraction for the concentrated solution of nickel after iron removal in the solvent extraction step is carried out using an acidic phosphoric acid ester-based extractant as an extractant.
6. The method for producing high purity nickel sulfate of claim 1 , wherein the nickel sulfate solution obtained in the solvent extraction step is converted to nickel sulfate crystals through a crystallization step.
7. The method for producing high purity nickel sulfate of claim 1 , further comprising a preliminary sulfurization step before the sulfurization step
the preliminary sulfurization including adding a sulfurizing agent to an acidic solution containing nickel, and preliminarily sulfurizing impurities that are more easily sulfurized than nickel to separate the impurities.
8. The method for producing high purity nickel sulfate of claim 1 , wherein the acidic solution containing nickel is a solution obtained by adding sulfuric acid or hydrochloric acid to any one or more of nickel oxide ore, nickel matte, nickel sulfide, mixed sulfide of nickel and cobalt, crude nickel sulfate produced by a copper smelting process, and nickel oxide, nickel hydroxide, nickel carbonate, nickel powder, nickel metal, a nickel hydrogen battery, a lithium ion battery, and defective products or partly finished products generated in the production processes thereof; and thereby leaching nickel.