Oxidative leaching of an offgrade/complex copper concentrate in chloride lixiviants

Abstract

Laboratory studies have been conducted on chloride leaching as a possible route for the simultaneous recovery of copper, zinc, and lead from an off grade and complex chalcopyrite concentrate (from Sikkim, India) associated with appreciable amounts of sphalerite, galena, and pyrite. The effects of temperature, concentration, and quantity of ferric chloride, stirring speed, and leaching time on metal dissolution have been investigated. Leaching tests have also been conducted with in-dividual (HC1, NaCl, CuCl2, FeCl3) and mixed chlorides (two-, three-, and four-component mix-tures). Results show the possibility of recovering not only 99 pct Cu and 89 pct Zn but also 82 pct Pb and 58 pct elemental S by treatment of the concentrate with 4 M FeCl3 at 383 K (110 °C) for 7.2 ks (2 hours) employing 25 pct excess FeCl3 and a stirring speed of 700 rev min-1. Though 64 pct iron of the concentrate is found to dissolve, the pyrite seems to remain unattacked. Kinetic studies indicate that the chalcopyrite, sphalerite, and galena of the concen-trate dissolve simultaneously in the FeCl3 lixiviant as if each mineral is separately leached, and the Cu and Zn dissolution reactions are under chemical control (linear kinetics). The addition of NaCl to the chloride lixiviants is found to be beneficial only up to a common salt concen-tration of 100 g/l. Leaching of the copper concentrate with CuCl2 or mixed FeCl3-CuCl2-NaCl has not been as effective as its direct leaching with 4 M FeCl3. © 1990 The Minerals, Metals & Material Society.