Dissolution Behavior and Kinetics of the Phosphorus–Potassium Associated Ore during Phosphoric Acid Leaching

The comprehensive utilization of the phosphorus–potassium associated ore has become significant to the new energy industry in China. This study proposes a new method for utilization of the phosphorus–potassium associated ore by phosphoric acid leaching. The mineral phase of the phosphorus–potassium associated ore was analyzed by X-ray diffraction and mineral liberation analysis. The leaching characteristics, mechanism, and kinetics of phosphorus, potassium, aluminum, magnesium, and iron were systematically investigated. Phosphorus and potassium leaching processes were controlled by the internal diffusion of the shrinking core model with apparent activation energies of 30.43 and 23.81 kJ/mol. The optimized leaching process conditions were as follows: stirring speed of 400 rpm, particle size of 150–300 μm, phosphorus concentration (P2O5) of 14%, phosphorus-to-calcium ratio of 9.65, reaction temperature of 40 °C, and reaction time of 60 min. The phosphorus leaching rate was 96.18 ± 0.92%, and the potassium leaching rate was 2.60 ± 0.08%. The acid-insoluble residue was mainly composed of potassium feldspar, indicating that effective separation of phosphorus and potassium was achieved through phosphoric acid leaching.