Effects of Particle Morphology On the Anti-Microbial and Anti-Adhesion Performances of Silver Embedded Polysulfone Membranes and Rate of Silver Leaching

Effects of Particle Morphology on the Anti-microbial and Anti-adhesion Performances of Silver Embedded Polysulfone Membranes and Rate of Silver Leaching

Meng Hu¹, Kai Zhong², Sheryl H. Ehrman², and Baoxia Mi¹

¹Department of Civil and Environmental Engineering, University of Maryland

²Department of Chemical and Biomolecular Engineering, University of Maryland

Keywords: silver nanoparticle, silver nanowire, silver microparticle, antimicrobial property, antifouling strategy, UF

Membrane technology has been gaining increasing attention due to water scarcity and the need for more sustainable water purification techniques. Biofouling, however, is a critical barrier to the wide application of membrane processes.  Silver, metal or ions, is an excellent anti-microbial agent. Composite membranes embedded with silver nanoparticles (npAg) have been reported to be able to alleviate biofouling and increase water flux by widening the finger-like structure in the cross-section. However, there are drawbacks such as high cost of silver nanoparticles and environmental/heath concerns caused by the release of silver ions/particles from membranes. Silver leaching also shortens membrane life. Therefore, it is imperative to find a way to maximize the anti-biofouling performance of silver while minimizing silver leaching.

This research evaluated three forms of silver, including npAg, silver nanowires (nwAg), and cage-like silver microparticles (mAg). The goal was to find how the morphology and area/volume ratio of silver particles may affect the antimicrobial/anti-adhesion performances of silver embedded membranes and the rate of silver leaching from the membranes. The silver embedded membranes were made via a phase separation process, by first blending polysulfone (PSf) polymer solution with npAg, nwAg, and mAg, then casting the solution on a support mesh, and subsequently soaking in a coagulation bath. Membrane morphology and topography were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Incorporation of silver particles in PSf membranes changed pure water flux and rejection rates, and slightly affected the hydrophilicity of the membrane. The membrane anti-microbial property was assessed with a model bacteria (Escherichia coli) using both the disk diffusion method and the colony counting approach. High anti-microbial efficiency was observed for membranes that incorporated each type of silver. The anti-adhesion performances of the silver embedded membranes were evaluated using a window-cell membrane filtration system coupled with a fluorescent microscope. The rates of silver leaching were also characterized and compared among the three membranes. This comprehensive comparison study will provide insights into the selection of silver particles with different morphologies as anti-biofouling additives in membranes.