Lithium Extraction from Lithium-Bearing Clay Minerals by Calcination-Leaching Method

Lithium is a significant energy metal. This study focuses on the extraction of lithium from lithium-bearing clay minerals utilizing calcination combined with oxalic acid leaching. The relevant important parameters, leaching kinetics analysis, and the lithium extraction mechanism were deeply investigated. The results demonstrate that a high lithium recovery of 91.35% could be achieved under the optimal conditions of calcination temperature of 600 °C, calcination time of 60 min, leaching temperature of 80 °C, leaching time of 180 min, oxalic acid concentration of 1.2 M, and liquid-to-solid ratio of 8:1. According to the shrinkage core model, the leaching kinetics of lithium using oxalic acid followed a chemical reaction-controlled process. XRD, TG, and SEM analysis showed that the kaolinite, boehmite, and diaspore phases in raw ore transformed into corundum, quartz, and muscovite phase in calcination products when the calcination temperature was higher than 600 °C. Moreover, the expansion of the interlayer spacing of minerals during the calcination process could promote the lithium release. During the leaching process, lithium present in the layered silicates was efficiently recovered through ion exchange with the dissociated H+ from oxalic acid. This study could provide a promising guide for lithium extraction from lithium-bearing clay minerals.