Leaching kinetics of iron from coal-series kaolin by oxalic acid solutions

Removal of iron from coal-series kaolinite and its kinetics by chemical leaching were investigated in this paper. The optimal removal rate of iron reaches 29.09% (the content of $Fe_2O_3$ decreased from 0.55 to 0.39%) under the conditions of 100 °C, 0.4 M $C_2H_2O_4$, and liquid-to-solid ratio of 4 cm3/g for 120 min. The leaching process was successfully described by the Avrami model and mainly controlled by internal diffusion control of shrinking core model, the apparent activation energy is 18.46 kJ/mol. The experimental results were consistent with the internal diffusion control of shrinking core model, improving acid concentration and leaching temperature could promotes the removal of iron from coal-series kaolin.