Recovery of Alumina from Magnetic Separation Tailings of Red Mud by Na2CO3 Solution Leaching

Abstract

Recovery of alumina from magnetic separation tailings of red mud has been investigated by Na2CO3 solution leaching. X-ray diffraction (XRD) results show that most of the alumina is present as 12CaO·7Al2O3 and CaO·Al2O3 in the magnetic separation tailings. The shrinking core model was employed to describe the leaching kinetics. The results show that the calculated activation energy of 8.31 kJ/mol is characteristic for an internal diffusion-controlled process. The kinetic equation $$ 1 - \frac{2x}{3} - \left( {1 - x} \right)^{\frac{2}{3}} = \left[ {2.548 \times 10^{ - 2} \times { \exp }\left( {\frac{ - 999.04}{T}} \right)} \right] \times t $$ can be used to describe the leaching process. The effects of Na2CO3 concentration, liquid-to-solid ratio, and particle size on recovery of Al2O3 were examined.