Dissolution kinetics of kaolin mineral in acidic media for predicting optimal condition for alum production

The dissolution kinetics and mechanisms of reaction of Batagbon Kaolin in sulphuric and fluosilicic acids were studied. Leaching temperature, acid concentration, particle size, solid-to-liquid ratio, and stirring speed were selected as process parameters. It is observed that the dissolution rate increases with decreasing particle size and solid-to-liquid ratio, and increases with stirring speed, acid concentration, and leaching temperature. The experimental results indicate that the dissolution rate is of mixed control via hydrogen ion [H+] action, with reaction order of 0.813 and the reaction kinetics can be expressed as K(m)t=[1-(1-x)(1/3)+ y/6[(1-x)(1/3)+1-2(1-x)(2/3)]. The activation energy of the process is determined to be 21.6 kJ/mol. The level of the product quality is also evaluated.