Thorough extraction of lithium and rubidium from lepidolite via thermal activation and acid leaching

Abstract

• A novel process combined with thermal activation and acid leaching was presented. • This process extracted 99.79% Li, which is far beyond that generally reported. • The collaborative efficient extraction of Rb (99.55%) was also obtained. • The content of Li and Rb in residues could be as low as 0.0031% and 0.0096%. • High ratio rate calcium sulfate whiskers were prepared using leaching residues. Currently, with the increasingly stringent requirements of carbon emissions and the rapid development of the new energy industry, the strategic position of lithium and rubidium has been elevated unprecedentedly. The higher extraction rate of lithium and rubidium from lepidolite mineral is of great significance for improving the production efficiency of their related chemicals from the source. In this study, the lepidolite was treated by the combined process of thermal activation and sulfuric acid leaching. The mechanism was discussed. The results showed that the lattice structure of lepidolite was destroyed and converted to the activated state during thermal activation. Afterwards, water quenching forced the activated slags to remain in this state, which was conducive to the subsequent acid leaching. The effect of various parameters on extraction efficiency was investigated. Under the optimal conditions, this process achieved the lithium extraction rate of 99.79%, which was far beyond the 90% generally reported in current researches, and also obtained an efficient extraction of rubidium (99.55%). The content of lithium and rubidium in residues could be as low as 0.0031% and 0.0096%, respectively. Additionally, the leach residues were reprocessed to the preparation of high aspect ratio calcium sulfate whiskers which not only reduced the generation of solid waste but also improved the economic value of the process. This process provided a novel and thorough technology for the extraction of lithium and rubidium from lepidolite.