Solubility of LiOH·H 2 O in KOH Solutions from 333.15 to 353.15 K: Pitzer Modeling and Optimized Evaporative Crystallization for Lithium Recovery

Lithium hydroxide monohydrate (LiOH·H 2 O) is a critical alkaline lithium salt for battery applications. The solubility behavior of LiOH·H 2 O in KOH solutions and its evaporative crystallization process were systematically investigated in this study. Solubility was measured from 333.15 to 353.15 K, and a Pitzer model was developed for this system, demonstrating an excellent correlation with the experimental data. In the LiOH–KOH–H 2 O ternary system, LiOH·H 2 O solubility increased with temperature but decreased with KOH concentration at fixed temperatures. During evaporative crystallization experiments, the effects of mixing intensity of the solution, heat-transfer temperature difference, evaporation temperature, and mother-liquor KOH concentration on both the purity of LiOH·H 2 O and lithium recovery rate were systematically examined. Optimized conditions (evaporation temperature: 343.15 K, heat-transfer temperature difference: 15.0 K, stirring rate: 300 rpm, and KOH concentration in mother liquor: 30 wt %) yielded a lithium recovery rate of 55.6% and product purity of 98.3%. This study provides thermodynamic insights and process guidelines for the efficient separation and purification of lithium hydroxide from alkaline solutions.