Selective recovery and efficient separation of lithium, rubidium, and cesium from lepidolite ores

Sulfation and decomposition were proposed to selectively recover lithium, rubidium, and cesium from lepidolite ore. The purpose was to solve the problems of high acid consumption and the difficulty of separating lithium and aluminum in the sulfuric acid method. First, the theoretical feasibility of the process was verified by thermodynamic calculations. The optimal parameters were determined according to the theoretical and experimental results. The extraction rates of lithium, rubidium, and cesium were 90.5%, 91.2%, and 89.4%, respectively, whereas those of aluminum and iron were only 0.08% and 0.02%, respectively. The selective extraction of lithium, rubidium, and cesium was realized, and 90.4% of sulfuric acid could be recycled during the process. Subsequently, the mechanism was discussed by XRD and SEM-EDS analysis. The first-step roasting was the sulfation process of lepidolite, and the second-step roasting was the decomposition process of partial sulfates. The separation of alkali elements and impurity elements could be realized by simple deionized water leaching. The production of Li2CO3 and single-alkali sulfates (K2SO4, Rb2SO4, and Cs2SO4) were obtained through the efficient separation methods of carbonization precipitation and solvent extraction. This process achieved the selective recovery and efficient separation of lithium, rubidium, and cesium from lepidolite ores. At the same time, the recycling of sulfuric acid was realized; it greatly reduced the amount of reagents, such as acid and alkali. It is an efficient, clean, and sustainable process for the utilization of lepidolite ores.