High performance cross-linked dehydro-halogenated poly (vinylidene fluoride-co-hexafluoro propylene) based anion-exchange membrane for water desalination by electrodialysis

We are reporting synthesis of novel cross-linking agent 1,4-bis(4-vinylbenzyl)-1,4-diazabicyclo[2,2,2]octane-1,4-diium) and cross-linked dehydro-halogenated poly (vinylidene fluoride-co-hexafluoro propylene) (DHPVDF-co-HFP) based anion exchange membranes (AEMs). Reported di-quatemized fluorinated polymer based AEMs are analysed for, stabilities, and different properties to assess their suitability for electrodialysis. Attractive structural features such as multi-cationic side chain, fluorinated main polymer chain, absence of S-N(2) mechanism, and beta-hydrogen elimination, are responsible for their excellent performance. Optimized splendid AEM (Cr-AEM/1.02) exhibited 23.5% water content, 1.02 x 10(-3) equiv/g ion-exchange capacity, and 5.7 x 10(-2) S/cm conductivity at 30 degrees C, which are superior than other 1,4-diazabicyclo[2,2,2]octane/imidazolium functional groups containing AEMs reported in the literature, or commercialized AEMs. Because of di-quatemized nature, high permselectivity (0.94-0.96) of the reported membrane (Cr-AEM/1.02) has been obtained chronopotentiometric and membrane potential studies. Relatively high limiting current density (I-lim) (2.36 mA/cm(2)) of Cr-AEM-1.02 provides a broad window to achieve fast electrodialysis under relatively high applied voltage/current without any electrode reaction. Further, about 95% current efficiency and 3.1 kWhr kg(-1) energy consumption confirmed efficient nature of Cr-AEM/1.02 for salt removal by electrodialysis.