Cation Exchange Membranes and Process Optimizations in Electrodialysis for Selective Metal Separation: A Review

Abstract

The selective separation of metal species from various sources is highly desirable in applications such as hydrometallurgy, water treatment, and energy production but also challenging. Monovalent cation exchange membranes (CEMs) show a great potential to selectively separate one metal ion over others of the same or different valences from various effluents in electrodialysis. Selectivity among metal cations is influenced by both the inherent properties of membranes and the design and operating conditions of the electrodialysis process. The research progress and recent advances in membrane development and the implication of the electrodialysis systems on counter-ion selectivity are extensively reviewed in this work, focusing on both structure–property relationships of CEM materials and influences of process conditions and mass transport characteristics of target ions. Key membrane properties, such as charge density, water uptake, and polymer morphology, and strategies for enhancing ion selectivity are discussed. The implications of the boundary layer at the membrane surface are elucidated, where differences in the mass transport of ions at interfaces can be exploited to manipulate the transport ratio of competing counter-ions. Based on the progress, possible future R&D directions are also proposed.

Thorium Removal, Recovery and Recycling: A Membrane Challenge for Urban Mining

“…In electrodialysis, the extraction, reconcentration and substitution operations are carried out without direct intervention of the electrodes [ 197 ]. They are placed at the end of the electrodialysis cells in order to maintain the electric potential difference between the compartments separated by the membranes ( Figure 9 ) [ 197 , 198 , 199 ].…”

Cation Exchange Membrane with Internal-Blocking Sites for Mono/Multivalent Ion Separation

“…25−27 A strategy to design internal-blocking sites/artificial ion channels involves synthesizing hybrid MCPMs using inorganic particles and polymer impurities. 28 The introduction of inorganic particles can achieve the desired perm-selectivity by increasing the compactness of the membrane matrix. enhanced the Na + conductivity under alkaline conditions.…”

Composite Anion Exchange Membranes Based on Quaternary Ammonium-Functionalized Polystyrene and Cerium(IV) Phosphate with Improved Monovalent-Ion Selectivity and Antifouling Properties

“…Much attention has recently been attracted to ion exchange membranes with enhanced monovalent-ion selectivity to solve the above problems, which are addressed in numerous experimental, theoretical, and review publications [ 15 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. Many strategies for designing these highly selective membranes have been developed to date; these strategies can be classified into several groups.…”