Preparation of polyethersulfone ultrafiltration membrane coated natural additives toward antifouling and antimicrobial agents for surface water filtration

Chitosan (CS) and polyphenon 60 from green tea (PGT) as natural additives were used in the preparation of antifouling and antibacterial polyethersulfone (PES) ultrafiltration membranes via the surface coating method. The effect of additive coating on fouling resistance and antibacterial properties were evaluated. The membrane characterizations were carried out using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and surface hydrophilicity by contact angle. The results showed that the optimized modified membrane (1 wt% CS/3 wt% PGT-coated PES, denoted as CS1PGT3) demonstrated better hydrophilicity than the pristine PES membrane. In addition, the CS1PGT3 membrane exhibited high BSA rejection (99.99%), relatively high flux recovery (78.78%), and the highest water flux (46.83 L/m2.h) among all modified PES membranes. After the CS1PGT3 membrane was immersed in different soaking solutions (i.e., acid, alkaline, and neutral) for 21 days, the stability of CS and PGT groups on the PES membrane was also confirmed. Moreover, during examination using surface water filtration, the removal rates of chemical oxygen demand, turbidity, and aromatic compounds were increased from 64.30%, 34.23%, and 62.78% to 88.22%, 64.18%, and 84.21%, respectively. The largest inhibition zone diameter (7.83 mm of E. coli) and highest antibacterial efficiency (99% of E. coli) were achieved, suggesting the outstanding antibacterial properties of the optimized modified membrane. Thus, the incorporation of CS/PGT into PES membrane via the surface coating showed promising method to enhance antifouling and antibacterial properties.