Comparison of chalcocite dissolution in the oxygenated, aqueous sulfate and chloride systems

Abstract

The dissolution of chalcocite in oxygenated, acid solution was studied in the sulfate and chloride systems. First stage chalcocite dissolution occurs at a rate seventy times faster in chloride solution compared to sulfate solution. This large difference is attributed to the formation of the CuCl 3 −2 complex which allows copper to be extracted into solution without oxidation of Cu +1 to Cu +2 at the particle surface. The first stage dissolution rate in the sulfate system is directly proportional to oxygen pressure and initial surface area. The activation energy of 31.5 kJ/mol is associated with oxygen adsorption on the particle surface. The first stage dissolution rate in the chloride system is directly proportional to chloride concentration and initial surface area. The activation energy of 22.6 kJ/mol is associated with chloride ion diffusion through the solution boundary layer to the chalcocite surface. The second stage dissolution rate in the chloride system is independent of all system variables except temperature. The activation energy for the second stage is 34.6 kJ/mole and is associated with a step in the anodic dissolution process.