PROCESS FOR PURIFICATION OF A AQUEOUS SOLUTION OF NICKEL SULFATE CONTAINING COBALT AND CALCIUM

摘要

The present invention provides a high-efficiency process for purification of a crude aqueous solution of nickel sulfate, which can increase cobalt treatment capacity and produce a purified aqueous solution of nickel sulfate with reduced cobalt and calcium concentrations by improving cobalt extraction efficiency in the exchange reaction. The process uses a multi-stage, countercurrent reaction tank system, wherein the aqueous solution of nickel sulfate is supplied as an aqueous phase to a last stage of the reaction tank system and a mixed organic solvent containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester as an extractant, loaded with nickel and diluted with a hydrocarbon to an extractant concentration of 20 to 30% by volume, is supplied as a organic phase to a first stage of the reaction tank system, while keeping the aqueous phase at a pH level of 4.5 to 5:5 in the last stage, and a calcium concentration and a nickel, cobalt and calcium total concentration in the organic phase at 0.4g/L or less and 25g/L or less, respectively, in the last stage.