A review paper on the extraction of potassium from non-soluble resources with the use of acid and alkaline solution and molten salts

Abstract

Fertilizers have been given significant attention due to their critical need for agriculture yield to meet the demand for food growth arising from population growth. The demand for potassium fertilizer (metric tons of K2O) has increased by 12% between 2015 and 2020. Therefore, the concern about the limited availability of soluble potassium resources in the southern hemisphere has become a key research focus for identifying alternative resources and technologies. This study presents a review of the fundamental knowledge of alternative technologies, such as acid leaching, hydrothermal and molten salt technology, as well as different alternative K-bearing silicate resources (ultrapotassic syenite, nepheline syenite, glauconitic sandstone and mica). Studies on fluxing agents proposed for the extraction of K+ based on different methods were analysed and compared. This paper offers a detailed overview of experimental kinetic analysis, kinetic and mechanism reactions, aims to improve the extraction technology and address relevant industry challenges. This review also reports on thermodynamic analysis of the mineral-salt/acid/alkaline systems, providing insights into the basis of industrial applications. Finally, the review provides opportunities and challenges of each technique and has shown that further techno-economic and process analysis are required to better identify the viability of each technique for large-scale industrial demonstration.