A Kinetic Study of the Aqueous Oxidation of ZnS in Dilute Solution at Acidic Media

Abstract

A kinetic study of the aqueous oxidation of ZnS in dilute HCl solution has been made in order to obtain foundamental data of the acidic leaching condition.
Deaerated HCl solution of pH 1∼3 and 10⁻¹∼1 M/L Cl⁻ is used as the acidic medium. The amount of ZnS suspended in the solution is 10⁻²∼10⁻¹ M/L.
The solution is maintained at a constant temperature between 25°∼30°C and stirred at 600 rpm.
The experimental results obtained are as follows:
(1) The main dissolution reaction of ZnS in the acidic solution is a type of H₂S formation and shows a parabolic dissolution behavior.
The reaction is diffusion control.
(2) The effect of pH on the dissolution rate of ZnS is linear and the rate of dissolution decreases as the value of pH increases.
(3) The presence of Cl⁻ ion acts on the dissolution of ZnS, especially at high temperatures.
(4) The relation between the dissolution rate of ZnS and the surface area of ore suspended in the solution is linear. Its rate increases propotionally with increasing area of the ore.
(5) The dissolution of ZnS is large at first and then decreases with the lapse of time. The decreasing rate of dissolution of ZnS is probably due to the increase of Zn²⁺ in the solution.