The influence of tartrate on cobalt cementation on a rotating zinc disc inzinc sulphate

Basic cobalt salts redissolve more easily than Co alloys; this is the major reason for cobalt redissolution during the technical purification of the z inc sulphate electrolyte before zinc electrolysis. The electrolysis is perf ormed using a very pure zinc sulphate solution. Co2+ is a harmful impurity in the electrolyte, and is therefore usually removed by cementation. This c ementation process is very slow. Cu2+ and Sb3+, which are used as cementati on aids, are added as CuSO4 and potassium-antimony-tartrate, KSbC4O6H2. 1.5 H(2)O, respectively. Laboratory scale experiments show that large amounts o f tartrate in the solution reduce the cementation rate of Co2+ significantl y. Accumulation of tartrate may cause operational problems in a zinc plant, (C) 2000 Elsevier Science B.V, All rights reserved.