Abstract
Polymeric ion-exchange membranes have come a long way since their invention, benefiting a wide range of processes, ranging from desalination to fuel cells. However, challenges such as alkaline stability, monovalent ion selectivity, cost-effectivity, and process sustainability largely persist. This work showcases alkaline stable anion-exchange membranes made by hot-pressing of a polyelectrolyte complex of poly(styrenesulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA). This completely aqueous production approach leads to especially dense (non-porous) saloplastic films with an excess of cationic groups, demonstrating good stability even at high salinities (up to 2 M NaCl). On key performance indicators for anion exchange membranes, such as water uptake (~40%), permselectivity (up to 97%), ion exchange capacity (1.01 mmol g−1), and resistance (2.3 O·cm2) the membranes show comparable values to commercial membranes. A drop in permselectivity at high salinities, however, indicates that the charge density of the membranes could be further improved. Still, what really sets these membranes apart is their natural long term (up to 60 days) stability at extreme acidic (pH 0) and alkaline conditions (pH 14) and a relevant monovalent selectivity of up to 6.3 for Cl− over SO42−. Overall this work showcases PDADMA/PSS based saloplastics as highly promising and stable anion-exchange membranes, that can be produced by a simple, scalable, and sustainable approach.
Highlights
The context of NASA’s Mars mission strategy - ‘‘Follow the water” is a world away, both literally and metaphorically, it precisely describes the very story of human settlements throughout history [1]
We propose that dense polyelectrolyte complexes could be very relevant as a new generation of sustainable ion exchange membranes, relevant for electrically driven processes
The objective of this study was to determine if a polyelectrolyte complex based plastic prepared by hot (80 °C) pressing (200 bar) a polyelectrolyte complex of Polystyrene sulfonate (PSS) and PDADMA can be used as an anion exchange membrane in electrodialysis
Summary
The context of NASA’s Mars mission strategy - ‘‘Follow the water” is a world away, both literally and metaphorically, it precisely describes the very story of human settlements throughout history [1]. Many technologies [4] have been developed to make potable water [5] and/or harness renewable energy [6] One such technology assisting man in both these spheres is electrodialysis, being used for seawater desalination [7,8,9] as well as for sustainable salinity gradient power [10,11], among other applications [12] Ion exchange membranes, which are mostly polymeric, make electrodialysis possible by selectively allowing certain ions to pass through them depending on their nature. While many commercial ion-exchange membranes have been developed, there is still a pressing need for more sustainable, pH stable [13,14], and economically viable membranes Such membranes could play a key role in energy storage, for example, in alkaline fuel cells.
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