Abstract
Li(3)PO(4) is a promising raw material for the low-cost synthesis of high-performance LiFePO(4). Reactive crystallization from low-concentration lithium-rich brine is a key process for the efficient preparation of high-quality Li(3)PO(4) products. The effect of operating conditions (temperature/supersaturation/impurities/ultrasonic) on the induction time was investigated using a focused beam reflectance measurement. The evaluation of the primary nucleation, growth kinetics, and parameters for the extraction of Li(3)PO(4) from low-concentration lithium-rich brine was conducted using an induction time method. The dominant mechanisms at different stages were inferred through online monitoring of the particle size distribution during the Li(3)PO(4) crystallization process. Results show that induction time decreases with increasing operating conditions (temperature/supersaturation/ultrasonic frequency), indicating that their increases all promote nucleation. Impurities (NaCl/KCl) did not significantly affect the induction time, whereas Na(2)SO(4) and Na(2)B(4)O(7) significantly increased it, with Na(2)B(4)O(7) showing the most notable effect. Classical nucleation theory was applied to determine kinetic parameters (nucleation activation energy/interfacial tension/contact angle/critical nucleus size/surface entropy factor). Results indicate that Li(3)PO(4) mainly nucleates through heterogeneous nucleation, with a temperature increase weakening the role of heterogeneous nucleation. Fitted models indicate that Li(3)PO(4) predominantly follows the secondary nucleation and spiral growth mechanism. Our findings are crucial for crystallization design and control in producing high-quality Li(3)PO(4) from lithium-rich brines.