Acid leaching kinetics of zinc plant purification residue

The leaching processes of zinc plant purification residue in sulfuric acid solution were investigated with respect to the effects of sulfuric acid concentration, reaction temperature, and particle size. A particle size of 75-80 μm was required to leach 99.8% cobalt and 91.97% zinc at 70 °C for 20 min when the sulfuric acid concentration was 100 g/L and the ratio of liquid to solid was 50?1 (mL/g). The leaching kinetics of zinc plant purification residue in sulfuric acid solution system conformed well to the shrinking core model, and the dissolution rates of cobalt and zinc were found to be controlled by diffusion through a porous product layer. The apparent activation energy values of cobalt and zinc reaction were calculated to be 11.6931 kJ/mol and 6.6894 kJ/mol, respectively, according to the Arrhenius formula equation. The results show that diffusion through the inert particle pores is the leaching kinetics rate-controlling step.