Abstract
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•Li, Rb, Cs and K were co-extracted effectively from lepidolite with rejection of Al.•A chlorination process using the mixed agent of CaCl2 and NaCl was investigated.•A leachate with few impurities was obtained, benefiting subsequent purification.•The mechanism and phase transformation of the chlorination process was explored.
Lepidolite is a precious multi-metal resources of lithium, rubidium, cesium and potassium. A chlorination process for efficient co-extraction of Li, Rb, Cs and K from lepidolite concentrate was investigated in this study. The lepidolite concentrate was roasted with a mixed chlorination agent of CaCl2 and NaCl at moderately high temperature followed by water leaching. The following optimal process conditions were identified: mass ratio of 30% CaCl2 and 20% NaCl to lepidolite concentrate, roasting temperature of 750 °C, roasting time of 45 min, water leaching temperature of 25 °C and liquid-to-solid ratio of 3:1. Under the optimal conditions, the extraction efficiencies of Li, Rb, Cs and K reached 92.49%, 98.04%, 98.33% and 92.90%, respectively. During chlorination roasting, the alkali metals in the lepidolite were transformed into water soluble chloride salts, along with the generation of insoluble phases, such as CaAl2Si2O8, CaF2 and NaAlSi3O8. After water leaching, a leachate with 5.15 g/L Li and few impurities such as aluminum was obtained, which was beneficial for subsequent leachate purification and metals recovery. This chlorination process is technologically feasible and potential for practical application.