Chlorine Leaching of Nickel and Cobalt Mixed Sulfide using Iron Chloride Solution

Abstract

The matte chlorine leach and electro ︲ winning （ MCLE ） process, developed by Sumitomo Metal Mining Co., Ltd. （ SMM ） is well known as a unique commercial nickel refining process with a high nickel recovery ratio. SMM has gradually increased the ratio of mixed sulfide （ MS: mixture of nickel and cobalt sulfides ） that can be used as a raw material in the MCLE process over the past decade. However, the reactivity of MS in chlorine leaching remains insufficient and further improvements are needed. We performed bench scale chlorine leaching tests with iron chloride, instead of the currently used copper chloride, as an oxi - dant medium for chlorine gas. However the reactivity of MS was not improved despite the higher oxidation ︲ reduction potential （ ORP ） of iron chloride than that of copper chloride. Though stability studies of iron chloride complexes based on an E ︲ pCl （ poten - tial, ︲ log a Cl ︲ ） diagram, the chlorine leaching potential that is suitable for copper chloride was found to be too low for iron chloride. Reactivity of MS was improved at a higher leaching potentials; however this did not represent a significant improvement over copper chloride based methods. We elucidated the reaction mechanism and showed that chlorine leaching with iron chloride is not suitable for industrial application to MS. ［ doi:10 . 2320 / jinstmet.J2016065 ］