Kinetics Studies of Sintered Nepheline Syenite Alkaline Leaching under Atmospheric Pressure

The purpose of this study is to develop the kinetic model and to find the optimum leaching conditions for maximum alumina dissolution from sintered nepheline syenite resource in the alkaline solution. About 80% of alumina (smaller than 5% of silica) was effectively recovered at 80 °C, 3 M NaOH, particle size less than 88 μm, agitation speed of 800 rpm, and leaching time of 60 min with a minimum amount of silica dissolution. Based on the kinetic model and the obtained reaction degree of each effective parameter, the experimental data were simulated. The simulation results proved that the leaching process for alumina was controlled by diffusion through the solid product layer and reaction at the interface of unreacted core that was confirmed by the value of activation energy (15.53 kJ/mol). The provided optimum conditions could be effective to decrease the silica dissolution, and to improve the alumina recovery.