The kinetics of enargite dissolution in chloride media in the presence of activated carbon and AF 5 catalysts

Abstract

This paper pertains to the kinetics study of atmospheric dissolution of enargite in chloride media with and without the addition of two different catalysts: (1) granular coconut shell based activated carbon (AC), and (2) a novel carbon-based catalyst with the commercial name of AF 5 Lanxess Lewatit® (AF 5). Unlike AC or other catalysts, AF 5 is capable of collecting solid sulphur particles on its surface during the atmospheric leaching process, leaving behind insignificant elemental sulphur in the oxidative leaching residues.The addition of both AC and AF 5 considerably enhance the leaching efficiency. Only 70% of copper was recovered in 96 h at 90 °C without the catalyst addition. The copper recovery was increased to 92% and 96% in the presence of AC and AF 5 respectively, in the concentrate to catalyst weight ratio of 1:1. The Cu2+ ions are found to be the main oxidant in the enargite leaching procedure. It was shown that the diffusion of Cu2+ ions through the product layer on the partially-leached enargite particles is the controlling step of the leach process, and the addition of the AC and AF 5 catalysts did not change the process controlling mechanism. The shrinking core model (SCM) has been used as the general kinetic model to study the enargite leaching kinetics at different temperatures. Scanning electron microscopy images of the partially-leached minerals confirmed that no impermeable elemental sulphur layer was formed on the enargite surface.