Selective Rubidium Recovery Using Zeolitic Potassium Hexacyanoferrate Nanomaterial Electrode in Capacitive Deionization

Rubidium (Rb) mining from seawater brine is promising as a sustainable renewable resource. Selectively recovering Rb from saline brine is challenging. Capacitive deionization (CDI), an electrosorption process, offers the capacity to extract Rb rapidly with selective electrodes. This study reports CDI electrodes utilizing potassium cobalt hexacyanoferrate (KCoFC‐AC) and ZIF‐embedded KCoFC (KCoFC@ZIF‐AC) nanomaterials for selective Rb uptake. The feasibility of the fabricated Rb‐selective electrodes is established by detail electrochemical characterizations. Compared to conventional carbon electrode, the fabricated electrodes exhibited a notably higher Rb selectivity. Specifically, the Rb uptake capacities of the composite electrodes with single Rb and mixed monovalent solution (Rb, Na, K) ranged from 78 to 127 mg g −1 and 57 to 103 mg g −1 , respectively. The enhanced performance of KCoFC@ZIF‐AC compared to KCoFC‐AC is attributed to the presence of the ZIF component, which promotes Rb penetration into the lattice structure of KCoFC. Moreover, the saturated electrodes demonstrated reusability multiple times with periodic chemical regeneration processes. In seawater, both fabricated electrodes exhibited an excellent Rb extraction rate (≈90%) with minor uptake of major cations (Na, Mg, K, and Ca). The superior Rb selectivity of the fabricated electrodes underscore the role of ion ‐exchange nanomaterial in CDI electrode for achieving rapid Rb extraction from brine.