The effect of the iron content of sphalerite on its rate of dissolution in ferric sulphate and ferric chloride media

Abstract

Fifteen sphalerite samples having solid solution iron contents ranging from 0.04 to 14.7% Fe were leached at 20–90%C in both 0.3 M Fe(SO 4 1.5−0.3 M H 2SO 4 and 0.3 M FeCl 3-0.3 MHCl media. Linear kinetics were observed for all the sphalerites in both leaching systems. The sphalerite leaching rate increased in a linear manner with increasing iron content. At 80°C in the ferric sulphate system, the rate, as defined by k=(1 −1 (1 − α) 1 3 )/t , increased from 0.38 gg −1 m −2 h −1 to 4.33 g g −1 m −2 h −1 as the iron content of the sphalerite increased from 0.04 to 12.5% Fe; the corresponding values in the ferric chloride system went from 0.26 g g −1 m −2 h −1 to 9.73 g g −1 m −2 h −1. Activation energies in the 39–81 kJ/mol range were observed in both systems. The activation energy decreased as the iron content of the sphalerite increased. The kinetics of sphalerite dissolution are similar in both the Fe(SO 4) 1.5H 2SO 4 and FeCl 3HCl system, and the sphalerite leaching reaction seems to be controlled by charge transfer at the sphalerite surface.