Method of solvent extraction of nickel sulfate solutions

摘要

A method of solvent extraction of a nickel sulfate solution uses a multi-stage, counter-current, organic solvent extraction system composed of at least two extractors connected in series, and includes a first extraction step of feeding a crude nickel sulfate solution that contains sodium and ammonium impurities into a second-stage extractor, wherein it is treated in countercurrent flow and at a pH of 6.5 to 7.0 with an organic extractant fed into the second-stage extractor from the first-stage extractor, to thereby extract some of nickel in the crude nickel sulfate solution into the organic extractant; and a second extraction step of transferring the nickel-containing, organic phase to an organic phase-scrubbing step to remove sodium and ammonium, while transferring the nickel sulfate solution, from the first extraction step and from which some of nickel has been removed, to the first-stage extractor, wherein it is treated in countercurrent flow and at a pH of 5.5 to 6.5 with a fresh organic extractant, to thereby extend the remaining nickel in the nickel sulfate solution into the organic extractant. The nickel-containing organic phase from the second extraction step is divided into two portions, one portion being fed into the second-stage extractor while the other portion is transferred to a by-pass, organic phase-scrubbing step it to remove sodium and ammonium.