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Improvement of Antifouling and Antimicrobial Abilities on Silver–Carbon Nanotube Based Membranes under Electrochemical Assistance

Fan, Xinfei, Liu, Yanming, Wang, Xiaochen, Quan, Xie, Chen, Shuo
Environmental science & technology 2019 v.53 no.9 pp. 5292-5300
antifouling activities, antimicrobial properties, asymmetric membranes, bacteria, biofilm, biofouling, carbon nanotubes, drinking water, electric potential difference, electrochemistry, nanosilver, organic matter, silver, water treatment
Excellent fouling resistance to various foulants is crucial to maintain the separation performance of membranes in providing potable water. Antimicrobial modification is effective for antibiofouling but fails to mitigate organic fouling. Improving surface charges can improve the resistance to charged foulants, but the lack of antimicrobial ability results in bacterial aggregation. Herein, a silver nanoparticle modified carbon nanotube (Ag-CNT)/ceramic membrane was prepared with enhanced antifouling and antimicrobial properties under electrochemical assistance. The presence of silver nanoparticles endows the composite membrane with antimicrobial ability by which biofilm formation is inhibited. Its steady-state flux is 1.9 times higher than that for an unmodified membrane in filtering bacterial suspension. Although the formation of organic fouling did weaken the biofouling resistance, the negatively charged bacteria and organic matter can be sufficiently repelled away from the cathodic membrane under electrochemical assistance. The flux loss under a low-voltage of 2.0 V decreased to <10% from >35% for the membrane alone when bacteria and organic matter coexisted in the feedwater. More importantly, silver dissolution was significantly inhibited via an in situ electroreduction process by which the Ag⁺ concentration in the effluent (<1.0 μg/L) was about 2 orders of magnitude lower than that without voltage. The integration of antimicrobial modification and electrochemistry offers a new prospect in the development of membranes with high fouling resistance in water treatment.