Abstract

Recent studies have demonstrated that monosodium glutamate has the potential to be used as a lixiviant for copper extraction from oxides and metals in alkaline conditions, but there is a lack of studies of its performance in mixed copper sulfide-oxide ores. The applicability of the system to treat complex copper concentrates and the kinetics of copper leaching into oxygenated, alkaline glutamate solutions were investigated. Based on a series of monosodium glutamate concentrations, dissolved oxygen levels, and temperatures, the work assessed the influence of these parameters on the recovery of copper from 3 concentrate samples. The increase of glutamate concentration, temperature, and dissolved oxygen levels increase the leaching rate, with up to 90 % copper extraction from concentrates A and B after 12 h at the best conditions (0.5 M glutamate, 60 degrees C, dissolved oxygen 15-20 ppm). Kinetic analysis following a shrinking core model suggested that copper dissolution is predominantly mixed controlled, with diffusion through a product layer becoming increasingly important at higher temperatures. The activation energy values calculated for each concentrate were consistent with a mechanism that is partially chemical and partially diffusion controlled, also consistent with the very slow leaching behavior of chalcopyrite-dominated concentrates. These leaching results indicate that monosodium glutamate has potential as a novel, truly green, zero-waste leaching agent for copper.