The Leaching Behavior of Potassium Extraction from Polyhalite Ore in Water

The extraction of potassium from polyhalite ore (K₂SO₄·MgSO₄·2CaSO₄·2H₂O) can help alleviate potassium resource shortages in China. In this study, the leaching behavior of potassium extracted from polyhalite ore in water was investigated using leaching experiments and kinetic analysis. The effects of various factors, such as liquid-to-solid ratio, leaching temperature, leaching time, and polyhalite ore particle size were comprehensively studied. It was found that high temperatures improved the reaction rate and efficiency at the beginning (1-15 min) but reduced the final leaching efficiency of potassium. And this phenomenon is discussed from the aspects of the dissolution-reprecipitation of potassium, newly formed solid products during the leaching process, and leaching thermodynamics. The leaching of potassium followed the Avrami model, with an apparent activation energy of 26.29 kJ/mol. Additionally, it was determined that the mixed controlled step (surface chemical reaction and diffusion) was the controlling step during potassium leaching. This study clarified the leaching mechanism of the polyhalite in water, and the causes of hindering the leaching of potassium were analyzed. The research results can provide theoretical reference and solutions for parameter design for the enhanced leaching process and selection of leaching agents in the future.