Silver nanoparticle impregnated rechargeable polyethersulfone (PES) membrane for biofouling prevention and water disinfection

Abstract

Abstract BACKGROUND Biofouling severely limits membrane life and performance. To address the twin challenges of biofouling prevention and water disinfection, silver nanoparticle (Ag‐NP) impregnated, sulfonated polyethersulfone (SPES) membrane was chosen. RESULTS By tuning the degree of sulfonation, Ag‐SPES‐1, Ag‐SPES‐2 and Ag‐SPES‐3 membranes were synthesized, having increasing Ag content of 4.1, 8.8 and 15.1 wt%, respectively. Time‐dependent confocal microscopy images of E. coli cells (after the passage of 10 4 CFU mL ‐1 ) show that all attached E. coli cells were killed in 5, 2 and 2 min for Ag‐SPES‐1, Ag‐SPES‐2 and Ag‐SPES‐3 membranes, respectively. However, Ag‐SPES‐2 shows maximum permeability coefficient (452 L m ‐2 h ‐1 bar ‐1 ) of decontaminated water in a cross‐flow module. This is because, Ag‐SPES‐1 takes a longer time for E. coli cell‐death due to its lowest Ag loading, whereas Ag‐SPES‐3 – due to excess Ag loading – results in the formation of an undesirable Ag‐NP layer on the membrane surface, leading to 16.7% decrease in its porosity. The latter translates into lower permeability. Fresh membranes showed the same permeability over six runs. However, to simulate the eventual depletion of Ag in the very long run, the membranes were recharged with Ag, upon which it showed similar permeability to a fresh membrane. CONCLUSION Therefore, the study achieved: (i) optimization of Ag content for highest permeability; (ii) recharging of membrane for prevention of biofouling‐initiation with both fresh and recharged Ag‐SPES membrane, leading to membrane reuse; and (iii) E. coli free disinfected water with Ag concentration (39 μg L ‐1 ), well‐within the permissible limit for drinking‐water (100 μg L ‐1 ). © 2017 Society of Chemical Industry