Leaching behaviour of a Bayer electrofilter fines in sulphuric acid

Sulphuric acid leaching of electrofilter fines Bayer Plant was investigated at different temperatures, using various particle size fractions and acid concentrations. Results showed that extraction was affected by acid concentration, initial particle size fraction and temperature of leaching. Aluminium dissolution in sulphuric acid increases as temperature does. At 90 °C, the increase in both acid concentration and reaction time has a positive effect on the extraction rate, which is also favoured by the decrease in particle size and solid:liquid ratio.The results of a leaching kinetic study are presented. Heterogeneity of the residue implies the existence of two different kinetics, the first one fundamentally due to the dissolution of the hydrate and the second one, being the case in study, due to the dissolution of transition alumina. The data obtained for the leaching kinetics in this second case, indicated that the dissolution of aluminium is a diffusion controlled reaction.