Enhancement of leaching efficiency for Li by phase transformation from lithium aluminum silicate (LAS) glass-ceramics

The mechanism of Li leaching from lithium aluminum silicate glass-ceramics was investigated to facilitate the recovery of Li. The experimental process was divided into the phase transition of the crystal structure through heat treatment and the Li leaching process using NaOH. Phase transition of the crystal structure based on the reaction temperature and heat treatment time was examined through X-ray diffraction analysis. The effects of the NaOH concentration, particle size, stirring speed, reaction temperature, solid/liquid ratio, and reaction time on Li leaching from heat-treated LAS was investigated. The results show that the crystal structure of lithium aluminum silicate glass-ceramics transitioned from hexagonal to tetragonal, and the efficiency of Li leaching from lithium aluminum silicate glass-ceramics before and after heat treatment was 68% and 99.6%, respectively. Accordingly, heat treatment increased the Li leaching efficiency by approximately 1.5-fold. To investigate the cause of the improvement of leaching efficiency, we calculated the lattice constant by using the interplanar spacing and Miller indices obtained from the X-ray diffraction analysis results for the respective powder samples. The results show that the crystal structure expanded approximately four-fold, and the reactivity with NaOH increased.