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Recovery of germanium and other valuable metals from zinc plant residues

The main purpose of this study was to characterize and to extract germanium from the copper cake of Cinkur Zinc Plant. The physical, chemical and mineralogical characterization of the ground copper cake sample obtained from Cinkur showed that it was 84% below 147 pin containing 700 ppm germanium. The copper cake also contained 15.33% Cu, 15.63% Zn, 1.66% Cd, 1.33% Ni, 0.64% Co, 0.35% Fe, 2.62% Pb, 12.6% As, 0.18% Sb and 3.42% SiO2. The mineralogical analysis indicated the complex nature of the copper cake which was mainly composed of metallic and oxidized phases containing copper, arsenic, zinc, cadmium, etc. The sulfuric acid leaching experiments were performed under the laboratory conditions. The optimum collective extraction of germanium and other valuable metals was obtained at a temperature range 60 to 85 degrees C for a leaching duration of 1 h with sulfuric acid concentration of 150 gpl and using a solid-liquid ratio 1/8 g/cc. Under these conditions, the recovery of germanium was 92.7% while the other metals were leached almost completely. The optimum selective leaching conditions of germanium was determined as half an hour leach duration, 1/8 g/cc solid-liquid ratio, 100 gpl sulfuric acid concentration and a temperature range 40 to 60 degrees C. Under these conditions the leach recovery of germanium was 78%. The dissolution's of other metals like cobalt, nickel, iron, copper, cadmium and arsenic were almost low. So, germanium would be separated more selectively at the following precipitation by tannin stage.