Present anion exchange
membranes are generally constructed by simple
and positively charged polymers with insufficient organic solvent
resistance, and exhibit a low selectivity in the separation of anions.
Here, dissolving poly(paraphenylene terephthalamide) nanofibers into
small nanofibers and performing a reaction with quaternary ammonium
groups in the one-dimensional small nanofibers, high-performance anion
exchange membranes were successfully fabricated. By increasing the
2,3-epoxypropyl trimethylammonium chloride content, the synthesized
amide nanofiber quaternary ammonium membranes (ANF#QA) exhibited a
higher anion exchange capacity (as high as 1.75 mmol·g–1) and achieved a high electrochemical performance. In electrodialysis,
the ANF#QA-10 membrane showed an exceptional Cl– selectivity in dilute and concentrated cells. Due to the dense structure
and presence of carboxyl groups on the nanofibers, the ANF#QA membranes
exhibited a selective separation of monovalent anions. After 48 h
of immersion in aqueous acetone solutions, the final ANF#QA-10 membrane
exhibited high desalination and concentration efficiency as the initial
membrane. This work highlights the promising use of positive charges
on small nanofibers, and proposes the design of a special anion exchange
membrane, which can be used for electrodialysis in organic solvent
solutions, and to selectively separate monovalent anions.
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