Antisolvent crystallization of lithium hydroxide monohydrate: Significant factors and kinetics analysis

Abstract Crystallization is the final stage in lithium hydroxide monohydrate (LiOH · H 2 O) production, and antisolvent crystallization offers a lower‐energy route compared with evaporative methods. In this study, we investigated bench‐scale ethanol‐based antisolvent crystallization of LiOH · H 2 O, and identified the significant impact parameter via a four‐factor, three‐level Box–Behnken design (29 runs). Effects of agitation rate (100–250 rpm), ethanol concentration (80–100 vol.%), organic‐to‐aqueous volumetric ratio (O/A ratio) (0.4–0.8), and temperature (20–40°C) on yield were reported. Statistical analysis showed that these factors acted independently rather than through combined interactions. The O/A ratio was the most dominant one: yield increased from ~10% at O/A of 0.4 to ~30% at O/A of 0.8. Ethanol concentration also had a strong effect with yield increasing from 5% at 80 vol.% to 26% at 100 vol.%. X‐ray diffraction (XRD) confirmed LiOH · H 2 O in all products, and scanning electron microscopy (SEM) showed that, unlike the compact blocky crystals formed by evaporative crystallization, ethanol antisolvent crystallization produced elongated plate‐like crystals featuring side projections. Crystallization kinetics were studied in a non‐seeded LiOH‐EtOH‐H 2 O system between 10 and 40°C. The %yield versus time at different temperatures were fitted well to the Avrami equation ( R 2 = 0.96–0.99) with very low exponents ( n = 0.14–0.5). This indicates that the ethanol antisolvent crystallization can be characterized by rapid nucleation followed by diffusion‐limited growth. Early‐time kinetics analysis using parabolic diffusion law produced a transport rate constant k p that decreased as temperature increasing. It indicates that ethanol antisolvent crystallization of LiOH · H 2 O is governed primarily by thermodynamics through supersaturation, rather than by simple diffusion.