Efficient extraction of Li and Rb from zinnwaldite via thermal activation and acid leaching

Lithium and its associated rubidium are regarded as the strategic metal resource, which have a wide use in many commercial products. Nowadays, the continuing growth in demand for Li resources, propelling the object of industrial exploitation will focus on low-grade, complex minerals composition and unwieldy ores. Zinnwaldite has received increasing attention as a potential lithium-containing resource in recent years. However, there are a lack of effective extraction processes for zinnwaldite. Hence, this paper proposes an effective method to extract metal cleanly and efficiently from zinnwaldite by using CaO and B2O3 as thermal activation additives and H2SO4 as the leaching agent. The results showed that the destruction of Fe-O and Si-O-Si bonds led to increased extraction efficiency. The breathing vibrations of oxygen atoms symmetric in 4- and 3-membered rings and Si-O symmetric stretch could influence the Li separation from silica skeleton. Ultimately, the 91.32 % Li, 93.09 % Rb, 81.14 % Fe, 95.00 % Al and 71.12 % K were recovered under the optimal conditions. Meanwhile, about 10 % F escaped into the air during thermal activation and the concentration of F in the leaching solution was lower than 2 mg/L. The use of B2O3 provides a valuable reference for the efficient and clean treatment of lepidolite using the salt roasting method.