Statistical Modelling of Sulphuric Acid Leaching of TiO 2, Fe 2O 3 and A1 2O 3 from Red Mud

Abstract

Sulphuric acid leaching of Ti, Al and Fe (which make up the ‘Red mud’ waste from Etibank Seydisehir Aluminium Plants, Turkey), has been studied using statistically designed experiments. The effects of five factors, namely: temperature, leaching time, acid normality, solid-to-liquid ratio, stirring rate on leaching yield of TiO2, Al2O3 and Fe2O3, have been investigated. Experiments have been planned by factorial design and orthogonal central composite design methods. The following models have been obtained by means of variance analysis at 92.5% confidence level. • YTiO2= 64.1087 − 5.2264 X1 + 22.6566 X2 − 1.3085 X3 − 9.2821 X4 + 1.4675 X5 − 7.0354 Xl2 − 5.8515 X22 + 1.2055 X42 + 8.9975 X1X2 - 2.6113 X1X4 − 1.7837 X1X5 + 1.5350 X2X3 + 1.9550 X2X5 + 2.9287 X3X4 − 1.3838 X3X5 • YFe2O3 = 13.2686+ 8.9664 X1+ 16.7172X2 − 10.2664 X4 + 3.2134 X5+ 6.9270 X22 + 4.2107 Xl + 9.9694 X1X2 − 4.7119 X1X4 − 7.6144 X2X4 + 2.5906 X2X5 − 5.5756 X3X5 • YAl2O3 = 68.2351 + 8.4249 X1 + 2.1984 X2 + 1.9705 X3 + 4.0853 X5 + 3.9794 Xl + 4.2312 X1 X2 − 2.7225 X1X4 + 3.1000 X2X3 + 2.5750 X2X5 where X1 is temperature, X2 is acid concentration, X3 is stirring speed, X4 is solid-to-liquid ratio, and X5 is reaction time