Leaching kinetics of potassium and aluminum from phosphorus-potassium associated ore in HCl-CaF2 system

The leaching behaviours of potassium and aluminum from phosphorus-potassium associated ore in HCl-CaF2 media were investigated at temperature from 60 to 90 degrees C. The higher dissolved fraction of potassium compared with aluminum was found in this study though they were mainly incorporated into the same mineralogical phase of potash feldspar in the ore. Moreover, the dissolved fraction of potassium was always higher than aluminum in all the investigated conditions due to the existence of secondary precipitation phase such as amorphous aluminosilicate or the formation of insoluble AlF complex in the leaching process. In addtion, the leaching kinetic data were successfully examined by a semiempirical kinetic model based on the classical shrinking core model. It was found that there are two distinct stages in the leaching process and the kinetics of both stages follows the semiempirical kinetic model with chemical reaction being the rate-controlling step. The activation energies for potassium and aluminum from the ore were 39.031 and 44.260 kJ.mol(-1) at first leaching stage, and 59.274 and 62.944 kJ.mol(-1) at second leaching stage, respectively.