PROCESSING OF UM-GHEIG LEAD-ZINC DEPOSITS, EASTERN DESERT, EGYPT FOR SEPARATING PURE CADMIUM SULFIDE

摘要

Lead-zinc mineralization is distributed in Egypt along the Red Sea coast between El Qusier and Ras Banas. A representative sample from Um Gheig was collected and ground to -60 mesh for the mineralogical study. It contains hemimorphite (Zn_2SiO_4·H_2O), sphalerite (ZnS), galena (PbS), calcite (CaCO_3) and dolomite (CaMg(CO_3)_2) beside the gangue minerals gypsum (CaSO_4·2H_2O) and hematite (Fe_2O_3). Cadmium seems to be incorporated in the crystal structure of the zinc-lead minerals. The chemical analysis of Um-Gheig representative sample revealed that, it contains 16% zinc combined with 0.1% cadmium, 2.3% lead and 0.1% boron beside other elements.Pug and agitation leaching were performed on samples ground to -200 mesh to achieve the maximum dissolution efficiency of cadmium with respect to other elements. Cadmium leaching efficiency reached 90% by using 40% H_2SO_4 at S/L ratio 1/2 and stirring time 2 hours at 80°C. Cadmium was then separated as yellow precipitate of CdS from the sulfate leach liquor containing 0.9 g/l Cd, 145 g/l Zn, 0.15 g/l B and 0.01 g/l Pb. Separation of cadmium was carried out by direct precipitation using Na_2S as well as H2S. The recovery of 94% cadmium free of zinc was achieved.