Recovery of zinc and lead from zinc extraction residue

V ABSTRACT MASTER THESIS RECOVERY OF ZINC AND LEAD FROM ZINC EXTRACTION RESIDUE M. Deniz TURAN Fırat University Graduate School of Natural and Applied Sciences Department of Metallurgy and Material Engineering 2002, Page: 78 Zinc production residues, obtained as a by product in production of metalic zinc by leach-electrowin process from carbonated ores, contain significant amount of lead besides zinc. These residues can be considered as a source for zinc and lead due to their high zinc and lead content. The recovery of valuable metals is extensively investigated from such metallurgical residues by means of hydrometallurgical techniques. In this study, recovery of zinc and lead from zinc extraction residue (ZER) obtained from Çin-Kur plant (Kayseri) was investigated. For this purpose, by using a process including subsequent two extraction stage, optimum conditions were determined for extraction of Pb and Zn from ZER that contains 24.64 % Pb, 11.30 % Zn, 8.34 % Fe and 5.21 % S as major components. In the first stage, ZER was roasted with concentrated H2SO4 and then subjected to leach operation by water in order to bring Zn into the solution. The optimum conditions for Zn extraction were determined as H2SO4/ZER ratio= 1, 200°C of roasting temperature, 30 min of roasting time, 25 °C of leaching temperature and 60 min of leaching time. Under these conditions, while 46.04 % of Fe and 86.32 % of Zn could be extracted, it was found that the Pb concentration of leach solution is about 8 mg/1. It was determined that the secondary zinc extraction residue (SZER), which is solid product obtained from first stage extraction, contains 30.56 % Pb, 1.60 % Zn, 4.69 % Fe and 7.31 % S by chemicalVI analyses. This residue was subjected to second stage extraction studies including chloride-leaching experiments in order to recovery of Pb. The conditions for significant Pb extraction obtained from SZER by NaCl leaching were determined as 20 g/1 of SZER/solution ratio, 200 g/1 of NaCl concentration, 25 °C of leaching temperature and 10 min of leaching time. Under these conditions, while the Fe concentration of leach solution was about 1-2 mg/1, extraction yields of Pb and Zn were 89.34 % and 17.49 %, respectively. As a conclusion, it can be stated that the significant amounts of Zn and Pb could be extracted separately by using this two-staged recovery process. The production of metallic Zn from the leach solution obtained at first stage seems possible by following subsequent cleaning and concentration treatments. On the other hand, it can be said that the Pb in the second stage leach solution could be recovered by means of a sulphide precipitation as a reach lead sulphide concentrate which is suitable for pyrometallurgical evaluation. Key Words: Zinc, Lead, Zinc extraction residue, Metal recovery, Sulphating roasting, Chloride leaching