China Nonferrous Metallurgy

It is difficult to achieve industrial production of low rubidium lepidolite because of the large differences in the occurrence forms of Rb. In this paper, the extraction of Li and Rb from rubidium-rich lepidolite ore in Australia was studied by using NaCl-CaCl₂ roasting-water leaching method. The effects of roasting temperature, ingredient ratio, time and leaching liquid-solid mass ratio, leaching time and temperature on the extraction of Li and Rb were investigated. The results show that under the conditions of rubidium-rich lepidolite ore∶NaCl∶CaCl₂ mass ratio of 1∶0.6∶0.4, roasting temperature of 800℃, roasting time of 1.5h, water leaching temperature of 25℃, liquid-to-solid ratio of 4∶1 and leaching time of 15min, the leaching effect of Li and Rb is the best. The leaching rates of Li and Rb were 87.8% and 94.9%, respectively. X-ray diffraction (XRD) analysis of calcinate and leaching residue showed that Li and Rb mineral phases in lepidolite transformed into soluble LiCl and RbCl phases after chlorination roasting, meanwhile KCl and insoluble substances CaAl₂Si₂O₈, NaAlSi₃O₈, CaF₂ were generated. The ΔG^Θ_T-T and ΔH^Θ_T-T diagrams showed that the reaction order of NaCl-CaCl₂ with alkali metal oxides was Rb＞K＞Li. The participation of SiO₂ and Al-O phase in ores promoted the chlorination reaction for alkali metals.