Improved anti-biofouling performance of polyamide reverse osmosis membranes modified with a polyampholyte with effective carboxyl anion and quaternary ammonium cation ratio

Publication date: Available online 4 October 2019Source: Journal of Membrane ScienceAuthor(s): Zhe Yang, Daisuke Saeki, Ryosuke Takagi, Hideto MatsuyamaAbstractBiofouling is a serious problem in reverse osmosis (RO) membrane processes. In this paper, a polyamide RO membrane was modified with a polyampholyte composed of anionic 2-carboxyethyl acrylate (CAA) and cationic [2-(acryloyloxy)ethyl] trimethyl ammonium chloride (TMA) by surface-initiated atom transfer radical polymerization, in order to improve its anti-biofouling properties. The anti-biofouling properties of membranes with different CAA/TMA surface ratios were evaluated by protein adsorption, static bacterial attachment, and long-term dynamic biofouling filtration experiments. It was found that an electrostatic attraction resulted in a severe biofouling, even if the water contact angle was 5–20° and the membrane hydrophilicity was sufficiently high. However, the RO membrane with CAA/TMA surface ratio of 1:1, fabricated from a mixed monomer solution with 3:1 CAA/TMA ratio showed an excellent anti-biofouling performance even in long-term dynamic biofouling filtration experiments. These good anti-biofouling properties derive from the high hydrophilicity of the membrane surface, resulting from its large content of ionic groups, and the almost complete lack of electrostatic attractions with charged bacteria, because the net surface charge is close to zero.
Source: Journal of Membrane Science - Category: Materials Science Source Type: research