Dissolution of sphalerite in ferric chloride solution

The dissolution of sphalerite in acidic ferric chloride solution of polished flat surfaces and of spherical particle surface was investigated. Tests were conducted on sphalerite to study rate of dissolution by the effects of stirring speed, temperature, ferric and ferrous concentrations, purity, and particle size.

Kinetic investigations were conducted in a nitrogen atmosphere with temperature ranges of 44°C to 90°C. The activation energy for the dissolution process is -11.2 ± 2.7 Kcal per mole.

The kinetics show chemical reaction as being important at the initial stages of leaching, and ion diffusion through a product layer as being important during the later stages of reaction. The mixed-control equation is an excellent description of the rate of dissolution of a sphalerite particle.

 K_rt = 1 - (1-R)^1/3 + B [1 - 2/3 R - (1-R)^2/3] where K_r = dissolution rate, min.^-1, t = leaching time, minutes, R = fraction of sphalerite converted, %, B = constant for mixed-control model.

The basic kinetic data of this investigation could be applicable to engineering design of the leaching process.