Anti-bacterial PVA@Ag/PVDF NF Membrane Made by Filtration-Coating Plus In-Situ Reduction of NPs for Dye Removal

In this study, a filtration-coating method was developed to create a PVA layer on a PVDF membrane, and then silver nanoparticles (Ag NPs) were introduced by in-situ reduction to form an antibacterial PVA@Ag/PVDF NF membrane. The relationship between the rejection of dye by the membrane, the morphology of the coated PVA layer and its coating process parameters, such as polymer concentration, crosslinking ratio, vacuum pressure, and time, was investigated. The filtration-coating method facilitated the infiltration of PVA molecules into the porous channel of PVDF membrane, thus improved the stability of coated PVA. Meanwhile, it was observed that high vacuum pressure (1bar), high polymer concentration (2%), and short filtration time (5min) have a similar effect to low polymer concentration (1%) and long filtration time (10min), which results in the formation of a dense layer structure (2-5 μm) on the membrane surface and leads to a high rejection rate but low flux. While filtration at low vacuum pressure (0.1bar) leads to a thin PVA layer (<0.2μm), and PVA turns to appear on the entrance and surface of pore channel of membrane. The coated membrane showed a stable performance during 72 hrs filtration. Furthermore, Ag NPs were incorporated into PVA layer by the in-situ reduction method, the obtained membrane showed an enhanced dye rejection (92% for methyl blue), and a low salt rejection (NaCl 18%) and moderate flux (17.2L·m-2·h-1 at 1bar). Moreover, the composite membrane demonstrated excellent antibacterial properties (Staphylococcus aureus and E. coli). Overall, this work may present a novel approach to prepare new NF membrane.