Study on Efficient Potassium Removal and Lithium Recovery from Potassium-Rich Mother Liquor

The potassium-rich mother liquor generated from the sulfuric acid process for lithium extraction from spodumene cannot be directly used for the production of battery-grade lithium salts, resulting in lithium resource loss. To address the issues of slow reaction rate and high seed crystal dosage in the traditional jarosite process for potassium removal, this paper systematically optimizes the type, dosage, and particle size of seed crystals based on the mechanisms of crystal nucleation and growth, ion occupancy competition, and interfacial crystallization-driven behavior. Results show that potassium jarosite seed offers high crystallographic compatibility, ease of preparation, and the best overall performance. Seed particle size must balance specific surface area and dispersibility; either too large or too small is detrimental to uniform crystal growth. Thermodynamic and kinetic analyses confirm that jarosite precipitation is strongly spontaneous and chemically controlled. Under the optimal process conditions (pH = 1.5, n(Fe3+)/n(K+) = 3.5:1, 1 g of potassium jarosite seed, 95 °C, 1 h), the potassium removal rate reaches (92.60 ± 0.48)%, and the lithium recovery rate is (95.20 ± 0.34)%. Lithium loss mainly arises from precipitate entrainment and insufficient washing; enhanced washing can further improve recovery. This study elucidates seed-mediated crystallization regulation and provides both theoretical guidance and technical reference for efficient potassium removal and high-value lithium recovery from potassium-rich mother liquor.