Controllable modification of polymer membranes by LDDLT plasma flow: Antibacterial layer onto PE hollow fiber membrane module

A high-density and uniform network-like antibacterial poly(methacryloxyethyl benzyl dimethyl ammonium chloride) (PDMAE-BC) layer was covalently constructed onto polyethylene (PE) hollow fiber membrane surface in a module scale via long-distance and dynamic low-temperature (LDDLT) plasma flow irradiation and subsequent graft polymerization. After the stepwise construction using this surface plasma chemical engineering method, the hydrophilicity of membrane surface was enhanced greatly due to implantation of numerous oxygen-containing groups. Meanwhile, the surface microstructures and chemical composition distributions were more uniform along with the axial distance from the module inlet and no significant damage/etching in membrane surface was observed. And even more prominent, the obtained PDMAE-BC membrane module can effectively destroy and/or inhibit bacteria by antibacterial layer, thereby preventing the formation of biofilms. It not only exhibited a high antibacterial activity against Gram-negative Escherichia coli, but also had an antifouling property, an increased water flux and an easy-cleanability. The antibacterial efficacy reached about 92.4% in the membrane module with only 10 PE-PDMAE-BC fibers and can be further improved by increasing the fiber packing density. In the long-term running, both original and PDMAE-BC membrane modules showed a 100% rejection ratio for E. coli. Moreover, the PE-PDMAE-BC membrane module can endure general water rinsing with little loss of antibacterial efficacy and exhibited an excellent antibacterial stability. This PE-PDMAE-BC membrane module should prove useful in actual water (mainly drinking water and wastewater) treatment.