Mixed matrix membranes based on morpholinium-functionalized CardoPES and MgAl-LDH: Structures, properties and electrodialysis performance

Abstract

A simple, inexpensive, and effective method based on the MMMs prepared from morpholinium-functionalized CardoPES and MgAl-LDHs is proposed to improve the ED capabilities of AEMs. The microphase separation and ED performance of mixed matrix AEMs were substantially enhanced by LDH introduction, which was attributed to the surface OH groups of the LDH nanosheets; these interactions induced polymer chain self-assembly. The AEM with 8 % LDH exhibited the highest salt flux (92.5 mg/m2·s) during ED, which was 19.6 % and 14.1 % greater than those of the commercial Type 10 membrane and the mixed matrix AEM, respectively. Hydrogen bonding interactions and the ED capabilities of the AEMs were readily regulated by adjusting the feed ratios of the LDH and morpholinium groups. With increasing LDH content, the Rm and ED performance increased, while the hydrophilicity and mechanical properties initially decreased. When the OH content of an LDH nanosheet was higher than the morpholinium content, as the LDH content increased, the Rm and ED performance decreased, while the hydrophilicity and mechanical properties increased, which may be attributed to internal structural discrepancies between the complete and incomplete core-shell structures of the AEMs caused by different hydrogen bonding patterns.