In situ immobilization of silver on polydopamine-coated composite membrane for enhanced antibacterial properties

In this work, the polyethersulfone (PES)-based membranes were prepared via phase inversion technique in the presence of polyvinylpyrrolidone (PVP) as a pore-forming agent. Polydopamine (PDA) coating followed by silver (Ag) immobilization was then carried out on the PES + PVP blend membrane to enhance the membrane wettability and antibacterial property, respectively. In total, four different membrane samples, namely pristine PES (M1), PES + PVP (M2), PDA/PES + PVP (M3) and Ag/PDA/PES + PVP (M4) were produced. The fabricated membranes were characterized with respect to physical morphology, contact angle, pure water permeability (PWP), humic acid (HA) and Escherichia coli (E. coli) rejection as well as antibacterial activity. The pristine PES membrane (M1) was reported to remove 77.81% HA and 96.4% E. coli. With the addition of PVP into the membrane matrix, the HA and E. coli rejection of M2 membrane was further improved to 79.94% and 99.33%, respectively. Upon PDA coating, the M3 membrane recorded much higher rejection rate (89.97% and 99.85%, respectively) owing to the formation of additional layer that reduced membrane pore size. It is interesting to note that complete elimination of E. coli was able to achieve by immobilizing Ag on the M4 membrane. This membrane also exhibited the greatest antibacterial activity and the highest HA rejection among all the fabricated membranes.