Surface modification of APA-TFC membrane with quaternary ammonium cation and salicylaldehyde to improve performance

• Aromatic polyamide thin film composite membrane was modified with QAC and SA.
• Chlorine resistance was visualized in the modified membrane.
• The modified membrane had perfect stabilities and powerful resistance to biofouling.
• High bacterial adhesion resistance and contact killing could be obtained.

The chlorine resistance and the anti-biofouling properties are the main characteristics of an aromatic polyamide (APA) thin film composite (TFC) membrane in the reverse osmosis (RO) desalination technology. In this work, quaternary ammonium cation (QAC) and salicylaldehyde (SA) were used to modify the membrane surface. QAC and SA can endow the membrane with the durable anti-biofouling properties by acting as the antimicrobial agents and bacteria contact-killers together, while QAC can endow the membrane with the high hydrophilicity by acting as the hydrophilic material, and SA endows the membrane with the high chlorine resistance by acting as the chlorine-consumer. The modified membranes were characterized by the Fourier transform infrared spectroscopy, the zeta potential analyzer, the contact angle analyzer and the scanning electron microscopy. The experimental results showed that the higher density of QAC and SA on the membrane surface led to the higher hydrophilicity, the stronger chlorine resistance and the more powerful anti-biofouling properties of the membrane.