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Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone
Published on: February 23, 2017
Hierarchical Membrane for Photoelectrostatically Gated Monovalent-Divalent Ion Separation
Enis Oğuzhan Eren1, Xuesong Xie2, Zhi Li2
1Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany.
Abstract:
Monovalent-divalent ion separation remains a significant challenge for the selective recovery of ions from aqueous solutions. Here, we report a hierarchical membrane composed of a poly(ionic liquid) photo-grafted onto a carbon nitride thin film supported on porous anodic aluminum oxide. Under concentration gradient-driven natural diffusion, the membrane establishes a baseline level of monovalent-divalent selectivity. However, upon application of light and bias as external stimuli, the hierarchical membrane enables light-assisted modulation of ion transport, resulting in a significant increase in monovalent-divalent selectivity by over 200 times for Li+/Mg2+ and over 500 times for K+/Mg2+. Ion selectivity arises from hydration-dependent mobility and electrostatic confinement within charged nanochannels. This work establishes a simple method to prepare hierarchical membranes for dynamically regulating ion transport and provides design principles for advanced monovalent-divalent ion separation.
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