Study on the roasting and leaching behavior of high-sulfur bauxite using ammonium bisulfate

High sulfur content is one of the many challenges in processing the refractory bauxites of China. A new method to prepare Al2O3 from high-sulfur bauxite with the NH4HSO4 roasting process was studied. The paper offers a possible alternative method for desulfurization of bauxite that may improve overall process economics and environmental impact. The roasting mechanism and various parameters including the amount of the ammonium bisulfate addition, roasting temperature and roasting time were investigated. The results showed that the control step of the roasting process was chemical control and the apparent activation energy was 65.74 kJ/mol over the reaction temperature range from 623 to 648 K. The leaching kinetics of the sintered clinker by water was investigated, which was affected by temperature, mass ratio of liquid to solid and time. Analysis of the kinetic data indicates that the dissolution of bauxite ore was controlled by the shrinking core with surface reaction model. The apparent activation energy of the leaching process was found to be 37.94 kJ/mol from 323 to 363 K. The maximum aluminum dissolution ratio reaches about 93% under the optimal condition. This paper aims at giving some revelation and instruction for the further research and practice on high sulfur bauxites development and application.