Tailored PVDF ultrafiltration membranes with quaternary ammonium salt for enhancing antibacterial efficacy

Abstract

Municipal sewage purification is an important means to alleviate water shortage. Polyvinylidene fluoride (PVDF) is a kind of ultrafiltration membrane widely used in water treatment but easy to incur biological contamination in the membrane separation process. Herein, a sequence of PVDF-based ultrafiltration membranes grafted with varying quaternary amines were designed to obtain fabulous antibacterial performance. Firstly, the antibacterial block copolymer composed of PVDF and quaternary ammonium salts is synthesized using the atom transfer radical polymerization technique. Subsequently, the copolymer is integrated into the matrix membrane through a phase inversion method. With a gradient change of alkyl chain lengths, we further explore the relationship between substituent structure and antibacterial properties. All functionalized membranes showed exceptional antibacterial activity with the highest efficiency of 83.3 % to E. coli and 69.1 % to E. faecalis. The as-anticipated properties were ascribed to the puncture effect shared by alkyl group and protective effect imparted by hydrophilic layer. During a series of cross-flow filtration experiment lasting for 10 h, the normalized flux retention was increased by a maximum of 1.52 times compared to pristine PVDF membrane. These results further highlight that the PVDF-based membrane functionalized by quaternary ammonium salt grafting is capacity of praiseworthy antibiofouling ability. Overall, our research provides a promising strategy to fabricate fouling-resistant ultrafiltration membranes and substantiates their potential utility in the realm of wastewater treatment.