Membranes for separation of alkali/alkaline earth metal ions: A review

Abstract The alkali metal and alkaline-earth metal elements, located in the adjacent main-groups of the periodic table, always have similar electronic structures and chemical properties. Thus, they are usually coexisting in ores or water resources. The separation of alkali metal ions and alkaline-earth metal ions has significant application prospect in seawater desalination, resource recovery and energy storage, which are paramount for the sustainable development of the environment, resources and energy. Membrane technologies have been investigated extensively in this area and have attracted widespread attention because of their advantages of environmental friendly and energy efficient. Accordingly, this work reviews recent advances in various types of membranes focused on the separation of alkali and alkaline earth metal ions, including organic membranes, inorganic membranes and mixed matrix membranes. Moreover, this review provides insights into the design and fabrication of membranes, the separation mechanisms, and the advantages and current challenges of each membrane.