Zwitterionic copolymer containing diallyldimethylammonium chloride and acrylic acid on carboxylated-MWCNTs

Plenty of procedures have been used to improve the hydrophilicity of membranes. The incorporation of carbon nanotubes has received a great deal of attention for this purpose. In this study, a zwitterionic copolymer, consists of diallyl dimethylammonium chloride, and acrylic acid moieties, was grafted to carboxylated-MWCNT via in-situ polymerization of monomers. The grafted copolymer simultaneously possesses positive and negative charges. The modification is done in a simple way, one step, and increases the hydmphilicity of the carboxylated-MWCNT significantly. FT-IR, FESEM, EDAX, and TGA were used to confirm the modification reactions. Nanocomposite membranes were fabricated by insertion of functionalized MWCNT into the PES casting solution. The effect of additives on membrane properties was investigated by the contact angle, porosity, zeta potential, swelling, morphology, and fouling studies. FESEM analysis showed that the cross-sectional morphology of membranes changed from finger-like to spongy. The hydrophilicity of the membrane surface demonstrated an incremental change afterward adding functionalized MWCNT. As a result of the increased hydrophilicity, the membrane fouling property improved significantly. The performance of the membranes in removing salts, heavy metals, and dyes was studied, and it was found that the membrane which has 5 wt% of the functionalized MWCNT had the best performance and at higher percentages, the efficiency decreased due to the accumulation between the additives. Moreover, the membranes are responsive to pH changes due to the presence of pH-sensitive additives, and studies have shown that the removal efficiency is improved under alkaline conditions.