Membrane technologies for monovalent/divalent cation separation

Efficient separation of monovalent/divalent cations is highly demanded in various industrial processes such as water softening, lithium extraction from salt-lake brine, the production of edible salt and the comprehensive treatment of acidic wastewater. Research on the above membrane materials used in these separation systems has advanced significantly in recent years. This paper presented a comprehensive review of the membrane-based technologies for monovalent/divalent cation separation, including selective cation exchange membranes, nanofiltration membranes, supported liquid membranes and ion imprinting membranes. The optimization strategies and underlying mechanisms for the membrane selectivity were highlighted. The characteristics and applicable scenarios of the above membrane processes were compared. Considering this, it was proposed that the selective ion separation was one of the key areas for membrane separation technology. Clarifying the formation and evolution mechanism of the separation layer at the molecular scale was crucial for improving the controllability of interfacial polymerization reactions. Highly selective ion screening can be realized by controllably constructing recognition sites and mass transfer channels for target ions inside the membrane matrix. Novel membrane materials contained intrinsic and regular pore architectures, such MOFs, COFs, two-dimensional layered membranes, etc., had good development potential for fine ion selection. © 2024 Chemical Industry Press Co., Ltd.. All rights reserved.