Leaching of Zinc Oxide in Acidic Solution

Abstract

Leaching mechanism of zinc oxide is important not only to understand zinc smelting process but also to develop of new zinc recycling process. Recycling of zinc is mainly done by treatment of electric arc furnace dust (EAF dust). In Japan pyro metallurgical process is enhanced for EAF dust treatment, however only zinc oxide can be recovered by pyro metallurgical process. Hydro metallurgical process makes it possible to recover high purity zinc directly from EAF dust. One of the main components of zinc included in EAF dusts is zinc oxide. Thus the mechanism of zinc oxide leaching is important to develop the new hydro metallurgical zinc recycling process. Leaching test of zinc oxide in hydrochloric acid and sulfuric acid solution has been carried out kinetically. Zinc oxide disk was used for leaching test which the reaction area is clear. The experimental parameters of pH, temperature, leaching time and rotating speed of the disk specimen were varied. The results obtained are as follows;
\\ oindent(1) The activation energy of leaching reaction by sulfuric acid was 17.5 kJmol⁻¹ and 11.6 kJmol⁻¹ by hydrochloric acid solutions.
\\ oindent(2) The leaching rate increases in proportion to the square root of rotating speed of test specimen.
These results indicate that the rate controlling factor of zinc oxide leaching reaction in acidic solution is mass transportation.