Cobalt, nickel and/or cadmium separation from zinc - in chloride solns. by sulphide cementation with zinc and sulphur

摘要

Co, Ni and/or C, and other metals which are more electro-positive than Zn, are selectively sepd. from chloridic Zn solns. by sulphiding cementation. The solns. are admixed with finely divided metallic Zn and elementary S powder, at higher temp. pref. 50-100 (60-80) degrees C. Suspension obtd. is stirred for a longer time and the pptd. metals are sepd. from the Zn soln. Zn-contg. intermediates or dusts contg. Zn at least partly in metal form, may be used, S can be replaced, entirely or partly, by reactive sulphides, e.g. ZnS or FeS. Dissolution of any pptd. Cd is prevented by avoiding activity of air or a long dwelling time. Other metals, eg. Ag, Cu, Pb and/or As are co-pptd. almost quantitatively. Fe and Mn are not pptd. Ni- and Co pptn. 90% can be achieved at 60-70 degrees C in 20-30 min. Cd pptn. reaches 70-90%. In a pref. process, sulphiding cementation takes place step-wise, in counter-current. Precipitants are added in last step. Ppte. and precipitant excess are contacted continuously with fresh soln. in counter-current. A 2- or multi-step cascade arrangement is used, with intermediate use of concentrators.