Modified zinc sulphate solution purification technique to obtain low levels of cobalt for the zinc electrowinning process

Zinc sulphate solution purification is very critical in the conventional 'r oast-leach-electrowin' process when adopting the hydrometallurgical route f or the production of zinc metal. Various purification methods are used in p ractice to achieve high quality neutral zinc sulphate electrolyte with mini mum levels of impurities. A modified single-stage zinc sulphate solution pu rification process is described in this paper with an aim to bring down cob alt to low levels. It involves a single-stage purification with two-stage o peration using potassium antimony tartrate (PAT), copper sulphate and zinc dust for the removal of impurities. The results obtained at both laboratory scale and plant scale and the optimum parameters to achieve the high quali ty solution are described. Chemical kinetics, copper requirement, zinc dust dosage and temperature for the removal of impurities and the composition o f the final purified zinc sulphate solution obtained are discussed. The pap er also compares the existing operating performance of the plant and the re sults obtained through this modified solution purification technique. This suggested new process is very simple and provides an improved electrolyte f or the down-stream electrowinning operation. (C) 1999 Published by Elsevier Science B.V. All rights reserved.