Kinetics of dissolution of zinc sulphide in aqueous ferric chloride solution

Studies on the kinetics of dissolution of chemical grade zinc sulphide powder in aqueous ferric chloride solutions of concentration range of 0.2 to 0.8 mol dm-3 at temperatures ranging from 30 to 70° C are reported. The dissolution rate follows a parabolic equation which fits well with the model of Crank-Ginstling and Brounschtein. The activation energy of the dissolution process has been found to be 90.0 ± 12.5 kJ mol-1. It is suggested that a film of elemental sulphur is formed on the zinc sulphide surface during its dissolution with ferric chloride. Inward diffusion of the ferric ion through this layer has been suggested to be the rate-controlling step