Liquid-phase mass transfer of ZnO-H₂so₄ solution system in an agitated vessel

Experimental and theoretical studies on the initial leaching rate of a spherical pellet of ZnO introduced in H₂SO₄ and H ₂SO₄- ZnSO₄ solution have been conducted to discuss the characteristics of liquid-phase mass transfer for ZnO-H ₂SO₄ solution systems in an agitated vessel. The results obtained are as follows: 1) For the ZnO-H₂SO₄ systems, the leaching rate is proportional to the 0.6th power of the stirring rate. The leaching rate increases with the concentration of H₂SO₄ and H⁺. 2) For the ZnO-H₂SO₄-ZnSO₄ systems, the leaching rate increases with the concentration of ZnSO₄. At a high concentration of H⁺, the rate is independent of the concentration of H⁺. 3) The leaching process for these systems is controlled by the liquid-phase mass transfer rate. 4) For the ZnO-H ₂SO₄ and ZnO-H2SO4-ZnS04 systems, the rates calculated by a mass-transfer model based on a film theory that takes into account diffusion and electrical migration are in good agreement with the experimental values at a low concentration of H⁺. However, the calculated values are not consistent with the experimental values at high concentration. This disagreement might be caused by the effect of chemical reaction at the ZnO surface.