Effects of Monomer Type on Polyphenol-Amine Codeposition and Its Application in Antifouling Modification of Anion Exchange Membranes (AEMs)

Abstract

Based on similar chemical structures and reactive sites with dopamine, polyphenols and some amines can react and generate adhesive polymers through oxidation and Michael addition/Schiff base reactions. In this study, four kinds of polyphenol-amine codeposition solutions were applied in surface modification of anion exchange membranes used in electrodialysis (ED). Catechol (CA)/tannic acid (TA) and m-phenylenediamine (MPD)/polyethylenimine (PEI) were respectively selected as polyphenol monomer and amine monomer, with chemical structural differences in the length of the carbon chain, the number of benzene rings, and functional groups. The effects of monomer type on copolymerization and codeposition process were investigated. Results showed that polyphenol types had important influences on chemical reactions and deposition. The codeposition solutions containing CA, especially the CA-MPD solution with two small molecular monomers, exhibited active and fast reaction rates, reflected in the changes in solution color and UV–visible absorption. By contrast, the flocculent between macromolecular monomers of TA and PEI changed the presence of solution, intermediates, and polymeric products, promoting deposition rates. In ED experiments, all modified AEMs maintained the desalination efficiency and demonstrated a better antifouling ability. However, the modified AEMs could not totally resist foulants and protect from the negative effects of fouling; regulating and improving codeposition modification need more investigation.