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Updated: Oct 11, 2026

Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone
Published on: February 23, 2017
Hydration channel engineering in Tröger's base-POP membranes for mono/multivalent cation and anion discrimination
Haopan Sun1, Ning Gan1, Baolong Wu1
1National Engineering Research Center for Comprehensive Utilization of Salt Lake Resources, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China.
Abstract:
Sustainable recovery of critical resources from complex aqueous streams is constrained by membranes that fail to combine rapid ion transport with precise mono/multivalent discrimination. Here, we report Tröger's base-derived porous organic polymer (POP) membranes with rigid, covalently crosslinked microporous frameworks that stabilize angstrom-scale transport channels while suppressing hydration-induced swelling. These membranes render rapid monovalent-ion transport with near-complete exclusion of multivalent cations and anions, including Mg2+, Al3+, SO42-, and PO43-. Experiments and simulations show that steric confinement, dehydration penalties, and electrostatic interactions cooperatively raise migration barriers for multivalent ions in confined channels. The membranes achieve comprehensive mono/multivalent discrimination across both cationic and anionic systems. In multistage electrodialysis, they enable stage-amplified lithium enrichment from high-Mg brines with stable long-term operation and downstream recovery of crystalline Li2CO3. They also facilitate high-purity NaCl enrichment from simulated seawater. Overall, this platform offers a durable and energy-efficient route to selective resource recovery from complex aqueous streams.
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