Potassium Recovery from Feldspar: Activation Routes, Dissolution Kinetics, Agronomic Performance, and Techno-Economic Assessment

Potassium feldspar has emerged as a strategic alternative source of potassium fertilizer, amid rising global demand and increasing reliance on imported soluble salts. This review critically analyzes research from 2016 to 2025 on the mechanisms of feldspar activation and potassium release, focusing on process kinetics, agronomic effectiveness, and economic viability. Recent improvements in activation techniques—including thermal and hydrothermal treatments, alkaline or chloride fusion, acid digestion, mechanochemical activation, and biolixiviation—have greatly enhanced feldspar reactivity, achieving potassium solubility levels of 80–95% under optimal fusion or chlorination conditions. Dissolution kinetics are primarily governed by surface reactions and diffusion, which are influenced by temperature, crystallinity, and the composition of the alkali flux. Agronomic tests demonstrate that fused or thermally activated feldspar can achieve 80–90% efficiency compared to KCl, offering sustained nutrient release and lower leaching losses. Cost estimates for processing vary from USD 60–100 per ton of K₂O using mechanochemical or hydrothermal methods, to over USD 200 per ton for fusion or chlorination, emphasizing the need for energy optimization. Environmentally, low-temperature and biological processes have the lowest carbon footprints and effluent outputs. Overall, feldspar activation methods present a promising path for sustainable potassium recovery, with future research likely to focus on integrated kinetic modeling, large-scale validation, and comprehensive life-cycle assessments to facilitate industrial implementation.