Robust antifouling anion exchange membranes modified by graphene oxide (GO)-enhanced Co-deposition of tannic acid and polyethyleneimine

Three polyphenol-polyamine co-deposition systems containing different polyphenols (catechol (CA), gallic acid (GA) and tannic acid (TA)) and Polyethyleneimine (PEI) were established and used to construct adhesive layer on the surface of anion exchange membranes (AEMs). And graphene oxide (GO) was introduced into co-depositions to construct an antifouling modifying layer. The modified AEMs were characterized and applied in electrodialysis for antifouling experiments. The results showed that the TA-PEI-M with a large depositing amount exhibited more hydrophilic surface than those of CA-PEI-M and GA-PEI-M, but still low value in the negative charge density. The introduction of GO increased the negative charge density of membrane surface and endowed AEMs with enhanced antifouling ability significantly. Furthermore, GO-TA-PEI-M could maintain surface properties and antifouling performance after immersing in NaOH solutions, indicating good alkaline-stability. It was attributed to that the abundant phenolic groups in TA played a vital role in the formation of co-deposition layer. The abundant phenolic groups in TA could provide stronger adhesion and multiple reactive sites to generate more stable covalent structures with PEI. In addition, the hydrogel products produced by the electrostatic interaction of TA and PEI helped increase the depositing amount. This work proposed a novel approach to fabricate surface-modified antifouling AEMs with alkaline stability by polyphenol-polyamine co-deposition.