Integration of silver nanoparticles and microcurrent for water filtration

Silver nanoparticles (AgNPs) have been incorporated into water filtration membranes as an effective agent for biofouling control. However, the antimicrobial efficacy of silver will be substantially reduced after sulfidation caused by sulfur species that are naturally present in many waters. To minimizing silver oxidation and flux loss, this paper proposed a novel strategy which integrates AgNP-impregnated membranes with low intensity electrofiltration technology. Polysulfone membranes incorporated with AgNPs or polyaniline nanofibers were fabricated by wet phase-inversion method. The membranes were connected to the cathode of a low intensity direct current source to form an electric field which facilitated electrophoretic force to direct aqueous ions. Without the presence of AgNPs, the low intensity electric activation alone did not exert a significant effect on membrane filtration efficacy or biofilm resistance. However, the combined effect of AgNP and electric activation resulted in a substantial biofilm reduction against both gram-positive and gram-negative bacterial strains over 24 h. The mass spectrometry and X-ray photoelectron spectroscopy showed that the cathodization preserved the metallic state of AgNPs for long period, and thus led to a superior performance than passive AgNP membranes. The integration of AgNP and electrofiltration extended the duration of biofouling resistance and minimized the silver leaching. It is a low-input, innovative approach that addresses the primary limitations of silver-based membrane technologies.