Abstract

Cupric chloride leaching is an attractive alternative for the treatment of pyritic refractory gold ores. In this context, the kinetics of pyrite dissolution was studied in cupric chloride solutions containing 4 M NaCl. Pyrite leaching experiments were conducted in a stirred tank reactor for 250 h. The effect of temperature was evaluated at 45 degrees C, 60 degrees C and 75 degrees C, while the effect of [Cu (II)] was evaluated with solutions containing 0.054, 0.252 and 0.512 M. The results showed that the increase in temperature and [Cu (II)] improved the rate of pyrite dissolution. The fraction of pyrite oxidised to sulphate ranged from 52% to 75%. Sulphate formation correlated well with the number of holes and cracks formed on leached pyrite particles. The kinetics of pyrite dissolution fitted well to the shrinking core model with chemical reaction control (T <= 60 degrees C and [Cu (II)] <= 0.054 M) or mixed control (T > 60 degrees C and [Cu (II)] > 0.054 M). The activation energy was 73.102 kJ/mol and the dependence of [Cu (II)] was proportional to [Cu(II)](0.230).