Purification and rapid dissolution of potassium sulfate in aqueous solutions

Abstract

Water soluble potassium sulfate dissolves rapidly and completely in water. Its main characteristics are purity and dissolution rate. In this study, the purification and rapid dissolution of potassium salt (K₂SO₄) separated from potassium brine deposits collected from Lop Nur basin of China (referred to as LN K₂SO₄) were studied for utilization in agricultural farming as a potash fertilizer. First, the dissolving-crystallizing process was conducted to remove the insoluble content and improve the purity of K₂SO₄. Second, physical modification of K₂SO₄ surfaces was accomplished based on the Noyes–Whitney equation. The results showed that the water insoluble content could be completely removed and the purity of K₂SO₄ reached 100% in the purification process. The dissolution rate was significantly improved with the help of environmentally-friendly additives such as sodium tripolyphosphate (STPP)/urea phosphate (UP). These additives ameliorated the diffusion coefficient (D) and the diffusion layer thickness (h) for K₂SO₄. Results also demonstrated that a larger K₂SO₄ surface area (S) induced a higher dissolution rate.