Advances in emerging separation technologies for rubidium recovery from seawater brines

The recovery of rubidium (Rb) from unconventional sources, including seawater and brine, is becoming attractive due to its growing global demand. Although seawater brine presents a sustainable alternative to traditional mining, the ultra-trace concentrations of Rb and competing alkali metals make the selective extraction particularly challenging. This review provides a concise overview of recent advances in sorbent design, including inorganic material-based sorbents, nanostructured sorbents such as metal-organic frameworks (MOFs), ion-imprinted polymers, and supramolecular sorbents, as well as integrated membrane-based recovery systems. First, existing brine mining technologies are summarized to provide a critical overview. Second, inorganic material-based pristine and hybrid sorbents are evaluated, which indicate that these sorbents offer improved selectivity due to tailored surface functionalities and structural adaptability. Notably, hybrid sorbents, especially those integrating inorganic sorbents with polymeric or magnetic supports, demonstrate improved stability, enhanced regeneration, and operational robustness. Third, the performance of emerging nanostructured sorbents and membrane-based integrated modules is critically analysed with regard to sorption capacity, selectivity, and scalability. Fourth, challenges and future research opportunities are outlined to bridge the gap between lab-scale performance and industrial implementation. The findings of this review provide a foundational framework for future innovation in sustainable Rb recovery and outline the broader potential of multifunctional sorbents in extracting Rb from complex matrices such as seawater brines.