Recovery of rubidium from brine sources utilizing diverse separation technologies

A rare alkali metal, rubidium (Rb) has significant economic value and emerging industrial applications including biomedical research, solar cells, atomic clocks, and electronics. Primarily Rb is recovered as an intermediate product during cesium or lithium extraction from pollucite or lepidolite, respectively. The rarity of Rb and its specific industrial usage have necessitated the development of new processes and the identification of alternative sources of Rb. As a result, alternative sources of Rb are becoming more appealing, primarily in the form of seawater brine and salt lakes. Researchers have utilized solvent extraction, precipitation, adsorption, and hybrid membrane-sorption technologies to recover Rb. A more in-depth evaluation of different separation technologies is imperative for achieving selective Rb recovery from complex brines. Hence, this assiduous review focuses on various Rb recovery technologies from brine. A specific emphasis is placed on Rb recovery by ion exchange-adsorption process in view of its efficiency, selectivity, and cost-effectiveness. Efforts to enhance adsorption are also discussed, including metal-organic framework grafting and encapsulation. This review will provide in-depth strategies for developing efficient and sustainable pure Rb recovery technologies having maximum adsorption capacity with improved kinetics, re-usability, and easier re-generation of the spent adsorbent from alternative brine sources.