Abstract:The aim of this work was to investigate the leaching of chalcopyrite concentrate in hydrochloric acid with hydrogen peroxide as a strong oxidizing agent. The effects of the leaching variables on metal extraction, such as stirring speed, solid-to-liquid ratio, temperature and HCl and H₂O₂ concentrations, were studied. The maximum final copper extraction of 33% was attained with 3.0 mol/L H₂O₂ in 0.5 mol/L HCl at room temperature after 180 min of the reaction. The results showed that the copper extraction was increased in the first 60 min of reaction, after which it essentially ceased due to the fast catalytic decomposition of hydrogen peroxide. Further, solid-to-liquid ratio affected the copper extraction significantly and the highest copper extraction was obtained in the most dilute suspension (i.e., S/L ratio of 1:100). The dissolution process was described by the first order kinetics equation. The apparent activation energy of 19.6 kJ/mol suggested that the dissolution process was under diffusion control. The reaction orders for HCl and H₂O₂ were established to be 0.30 and 0.53, respectively. The results of the XRD and SEM/EDS analysis of the leaching residue indicated the generation of the elemental sulphur on mineral surfaces which tended to inhibit the leaching rate.

Key words: chalcopyrite; leaching; hydrogen peroxide; hydrochloric acid; sulphur