Synthetic Alkali Aluminosilicate-Hydroxide Systems as an Analogue to Optimize Lithium Recovery from LCT Pegmatites

Abstract

In a study focusing on alternate energy-efficient approaches to recover lithium from LCT pegmatites, we demonstrated that single-stage decomposition of α-spodumene in caustic media can be achieved below 450 °C without the conventional pretreatment at temperatures exceeding 1000 °C, typically required to induce a phase transition to the more reactive β-form (Gamage McEvoy et al. in Energy technology 2023, TMS Springer, pp 81–87, 2023). Considering the challenges in characterizing and monitoring the evolution of lithium, an experimental phase stability study using synthetic sodium aluminosilicates analogues along the NaAlO₂-SiO₂ join (e.g. carnegieite: NaAlSiO₄) exposed to melted KOH was undertaken. The findings will be discussed in the context of optimizing the extent of alkali exchange and effective partitioning of silica and alumina in the solid residue that has implications for achieving selective lithium recovery in the pregnant leach solution.