Dissolution kinetics of iron and aluminium from red mud in sulphuric acid solution

263-268Dissolution kinetics for the removals of iron and aluminium from red mud, a by-product or waste of the Bayer Process, with sulphuric acid were studied. The process parameters studied include calcination temperature, sulphuric acid concentration, particle size, agitation rate, dissolution temperature and time. Temperature and acid concentration had strong influence on the dissolution of iron and aluminium. The mechanism for the dissolution of both iron and aluminium followed first order kinetic model equation (F1), -ln(1-α) = kt, controlled by interfacial chemical reaction, with the apparent activation energies of 61.42 and 7.39 kJ/mol, respectively. Using 6 M acid, the removals of 97.46% iron and 64.40% aluminium were achieved from red mud calcined at 873 K