Leaching kinetics of iron from low grade kaolin by oxalic acid solutions

Kaolin is a clay with important industrial applications. Unfortunately, with iron oxides depositing on mineral particles during kaolin formation, much of this clay has become unusable for industrial applications. Two of the most important factors that affect the value of this raw material are its iron concentration and brightness. The goal of this work was to examine the leaching kinetics of iron from low grade kaolin using oxalic acid solutions. The effects of particle size, acid concentration, and reaction temperature were studied. It was determined that the iron dissolution rate increases with oxalic acid concentration, temperature, and decreased particle size. Leaching data showed that iron dissolution from low grade kaolin is due to diffusion through the product layer. The activation energy of the process was 46.32 kJ/mol. (C) 2011 Elsevier B.V. All rights reserved.