Purifying surface waters contaminated with natural organic matters and bacteria using Ag/PDA-coated PES membranes

Abstract

Polymeric membrane is susceptible to fouling particularly when it is used to treat surface water contaminated by natural organic matters and bacteria. Surface modification may address the issue by imparting antifouling and antibacterial properties to the membrane. In this study, a neat polyethersulfone (PES) membrane (denoted as membrane P1) was prepared by phase inversion method followed by polydopamine (PDA) coating to improve its membrane hydrophilicity. Thereafter, the physicochemical properties of the PDA-coated PES membrane (denoted as membrane P3) were further improved by in situ reduction of silver (Ag) onto its surface to impart antibacterial properties (denoted as membrane P4). All membranes were instrumentally characterized while their filtration performance against humic acid (HA) and antibacterial properties were evaluated. Results showed that membrane P1 removed 77.81% of HA and achieved a fouling recovery rate (FRR) of 65.72%. Upon Ag immobilization, the HA rejection of membrane P4 was further improved to 95.14% with FRR recorded at 92.17%. This membrane also demonstrated good stability and excellent antibacterial properties over other fabricated membranes (P1, P2 and P3) in this study. Moreover, it exhibited a lower total flux decline and higher contaminant removal performance over membrane P1 in treating surface water samples.