Kinetics of iron leaching from kaolinitic clay, using phosphoric acid

Abstract

Kaolin is important because it has many applications in the paper, paint-coating, functional filler, extender and pigment industries. This material needs to be bleached by iron leaching to be useful for these applications because this element can be the principal cause of its undesirable coloration. In this work, the kinetics of leaching of iron contained in kaolin clays from the community of Agua Blanca Iturbide, Hidalgo, Mexico, was studied. The leaching experiments were carried out using phosphoric acid as the reagent of leaching for the iron dissolution process. Temperature, acid concentration, and particle size were investigated to determine the most important kinetics parameters during iron leaching. It was determined that the rate of iron dissolution increases with increasing of phosphoric acid concentration, the temperature, and decreased particle size of clay. Data obtained showed that iron dissolution from kaolin clay is due to the diffusion of iron through the product layer. The results revealed that the activation energy of the process was 10.18 kJ mol-1.