Factorial experiments for selective leaching of zinc sulphide in ferric sulphate media

The zinc-recovery results obtained in leaching tests run on a complex sulphide ore of Caribbean origin have been statistically processed. The raw material contained 6.95% Zn, 2.41% Pb and traces (0.05%) of Cu, The study was conducted by means of consecutive factorial plans which permitted determination of the manner in which the leaching was influenced by the following factors: (1) oxidizing agent (Fe-2(SO4)(3)) concentration; (2) temperature; (3) ore particle size characteristics; and (3) solid/liquid ratio. A regression equation was calculated by the results obtained from the tests; this permitted the derivation of a response surface which provides zinc recovery levels in relation to the levels of the factors adopted in the experiments. It is important to understand the parameters which exert most influence on zinc recoveries during leaching, especially when the presence of finely distributed polluting agents in the useful phase, pyrite in this case, prevents zinc enrichment by the usual physical means. (C) 1998 Elsevier Science B.V. All rights reserved.