Kinetics on leaching of potassium from phosphorus-potassium associated ore in HCl-H3PO4 media

In order to relieve the equipment corrosion, reduce chlorine and increase phosphorus contents in leaching solution, the leaching behavior of potassium from phosphorus-potassium associated ore in the mixed acids of hydrochloric acid and phosphoric acid was investigated. The effects of various factors, such as mass fraction of hydrochloric acid, solid-to-liquid ratio, material ratio (CaF2 dosage (g)/mass of ore (g)) and leaching temperature were comprehensively studied. It was found that the dissolution fraction of potassium can reach more than 86% under the optimum conditions of leaching temperature 95 °C, HCl concentration 10%, leaching time 6 h, solid/liquid ratio 1:5, and material ratio 0.1. In addition, the leaching kinetics of potassium was successfully modeled by a semi-empirical kinetic model based on the classic shrinking core model. The data showed that the leaching process of potassium was controlled by the product layer diffusion and the apparent activation energy for the process was found to be 54.67 kJ/mol over the temperature range from 65 to 95 °C.