Direct and efficient in situ rubidium extraction from potassium chloride salts

Rubidium (Rb) is a valuable rare alkali metal that plays a crucial role in various high-tech applications, but extracting Rb from conventional sources poses sustainability challenges. A considerable amount of Rb is found in potassium chloride (KCl) salts, which can serve as a sustainable source depending on the extraction methods. Current liquid-phase methods are problematic due to the low Rb/K separation factor and high consumption of energy, water and chemicals. Extracting Rb directly from solid KCl salts is a promising approach, but achieving efficient recovery remains a challenge. Here we propose a crystal ripening microextraction strategy that enables in situ extraction of Rb from solid KCl salts with high selectivity, simplicity and high efficiency. By applying this strategy, we recovered 92.37% of Rb from KCl salts with an initial Rb content of 113 ppm. Compared with liquid-phase extraction, our approach results in a 97.57% reduction in energy consumption, a 22.24% increase in recovery efficiency and a 13.46-fold higher Rb/K separation factor, which substantially enhance environmental and economic benefits. In addition, this approach is suitable for recovering other target metals needed for various industrial applications directly from different solid metallic salts, providing a pathway to improve the sustainability of critical metal supply. Sustainably extracting rubidium (Rb), a valuable critical metal, from alternative sources remains challenging. Here the authors report a crystal ripening microextraction strategy that allows efficient Rb extraction from potassium chloride salts, with large environmental and economic benefits.