20 Years Advances in Preparation of Potassium Salts from Potassic Rocks: A Review
Long‐term research on key techniques of clean utilization of potassic rocks from over twenty localities has been performed to settle the shortage of soluble potassium resources in China. The results show that K‐feldspar as the principal mineral enriched in potassium could be decomposed in the media of Ca(OH)2, NaOH, KOH‐H2O solution via hydrothermal treatment, into tobermorite, hydroxyl‐cancrinite, and kalsilite respectively. By further processing, these compounds are feasible for being as slow‐release carrier of potassium nitrate, extracting alumina, and preparing farm‐oriented fertilizers of potassium sulphate and nitrate. Correspondingly, the filtrate is KOH, (Na, K)2SiO3, and K2SiO3 solution, from which potassium carbonate, sulphate, nitrate, and phosphate could be easily fabricated. As NaOH and KOH are recycled in the processing chains by causticizing sodium and/or potassium metasilicate solutions, the hydrothermal alkaline techniques as developed in this research have several advantages as lower consumption of disposable mineral resources and energy, maximized utilization of potassic mineral resources, as well as clean productions etc. Based on the approaches presented in this paper, the technical system of efficiently utilizing insoluble potassium resources has been established. The hydrothermal alkaline methods are feasible to be industrialized on a large scale, thus resulting in decreasing imports of potash fertilizers, improving the pattern of potassium fertilizer consumption, and enhancing the supplying guarantee of potassium resource in China.
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