Leaching behaviors of copper and arsenic from high-arsenic copper sulfide concentrates by oxygen-rich sulfuric acid leaching at atmospheric pressure

Abstract

High arsenic copper sulfide concentrates (HACSC) are becoming increasingly common in the world. Copper pyrometallurgy brings a series of problems, such as arsenic-containing dusts and waste acids that are difficult to treat. Hydrometallurgical process is an attractive alternative to treat HACSC. This work dealt with the leaching behaviors and kinetics of copper and arsenic from HACSC by oxygen-rich acid leaching at atmospheric pressure systematically. The leaching temperature, oxygen flux, liquid-solid ratio, sulfuric acid concentration and time have significant effect on the leaching of copper and arsenic. However, the effects on the copper leaching efficiency were much greater than that on the leaching efficiency of arsenic. The experimental optimization conditions were obtained as follows: temperature 80 °C, liquid-solid ratio 20:1, stirring speed 400 r·min-1, oxygen flux 2 L·min-1, sulfuric acid concentration 270 g·L-1. Under these conditions, > 99% copper was leached within 18 h, > 95% arsenic was leached within 36 h. The X-ray diffraction (XRD) and Scanning Electron Microscope/ Energy Dispersive Spectrometer (SEM/EDS) studies confirmed that the changes in the phases and morphologies before and after the leaching processes corroborated the leaching behavior of copper and arsenic. Furthermore, copper leaching kinetic model followed the shrinking core model of the couplings control of diffusion and surface chemical reaction. The activation energy was 36 kJ/mol. The kinetic equations for the effect of leaching temperature, oxygen flux and sulfuric acid concentration were obtained, respectively. The overall kinetic equation which can be applied in solids with particle families of limited size was also developed.