LEACHING KINETICS FOR RECOVERING ALUMINA FROM WASTE TRICALCIUM ALUMINATE GENERATED AFTER FILTRATION OF BAYER'S LIQUOR

摘要

A study was performed on the leaching kinetics to recover the alumina from Tricalcium aluminate (TCA) generated as waste after removalrnof suspended red mud particles in the Bayer process by different concentrations of Na_2CO_3 solution at different temperatures andrnsolid:liquid ratios. The influences of initial sodium carbonate and stirring speed on reaction rate constant were examined and therncorresponding apparent activation energy was calculated. The results indicate that the leaching process is a first order reaction, and thernreaction rate constant 8.64×10~(-6) mol/(L.m). Optimization of recovery and minimization of Na_2CO_3 in liquor were studied, and therndissolution rate of TCA and conversion of CaCO_3 also increases. The apparent activation energy is 52.86 kJ/mol, and temperature has greatrninfluence on the leaching rate of TCA. The leaching rate is controlled by diffusion of reacting reagents in the solid product layer. A higherrnleaching rate of TCA is obtained by higher temperature and/or lower solid g/l during leaching process..