Review on K-Feldspar Mineral Processing for Extracting Metallic Potassium as a Fertilizer Resource

The K-feldspar mineral is an insoluble potassium resource with a high potassium content and the most extensive and abundant reserves. To address the insufficient supply of soluble potassium fertilizers in China, the application of appropriate processing methods to extract potassium from K-feldspar and transform it into a soluble potassium fertilizer is of great significance. To date, various techniques have been developed to extract potassium from K-feldspar and produce a soluble potassium fertilizer. This review summarizes the main methods, i.e., the hydrothermal, high-temperature pyrolysis, microbial decomposition, and low-temperature methods, for potassium extraction from K-feldspar. The mechanisms, efficiencies, impact parameters, and research progress of each potassium extraction method are comprehensively discussed. This study also compares the merits and drawbacks of the individual methods in terms of potassium extraction efficiency and practical operating conditions. The species of additives, reaction temperature, reaction time, particle size of K-feldspar, and dosage of additives significantly affected the potassium extraction efficiency. Moreover, the combination of different methods was very effective in improving the potassium extraction efficiency. This review elaborates the research prospects and potential strategies for the efficient utilization of the K-feldspar mineral as a fertilizer resource.