Kinetics of leaching of zinc ferrite in aqueous hydrochloric acid solutions

The dissolution of synthetic samples of zinc ferrite in aqueous hydrochloric acid is stoichiometric. The rate appears to be controlled by a chemical reaction on the solid surface, and dependence of the dissolution rate on hydrochloric acid activity is of the first order. Activation energy of 83 kJ mol^-1 was found. Zinc ferrite leaching is a slow solubilization process in the hydrochloric acid treatment of dead-roasted Iberian pyrite ashes. The most favorable conditions are 0.5-1 M HC1 at 90 to 100 ‡C, when preferential solubilization of the spinel phases takes place on the hematitic matrix. Extensive extraction of zinc (~90 pct of total zinc) in one to two hours and low solubilization of iron (~8 pet of total iron) results under these conditions.