Surface-concentrated chitosan-doped MIL-100(Fe) nanofiller-containing PVDF composites for enhanced antibacterial activity

Antibacterial properties are a major issue for the membrane-based wastewater treatment since the biofilm on membranes generated by bacterial growth can significantly reduce water flux. Here, the surface-concentrated MIL-100(Fe)/chitosan (MIL100-CS)-embedded polyvinylidene fluoride (PVDF) composite membranes (i.e., PVDF-S/MIL100-CS) were successfully fabricated by the newly developed fabrication method, so-called solvent-assisted nanoparticle embedding (SANE). The SANE method was modified from the conventional nonsolvent-induced phase separation method by the addition of an intermediate step for the selective arrangement of hydrophilic nanofillers on top of the nascent PVDF film. The additional step in the SANE method enabled the surface-selective filler distribution with the open surface of fillers, resulting in the hydrophilic surface. Also, it facilitated to form the sponge-like pore structures mostly due to the dilution effect of additional solvent. The PVDF/MIL100-CS microfiltration (MF) composite membranes acquired by SANE exhibited the higher antibacterial activity and the substantially enhanced biofouling resistance for E. coli cells than those of the pristine PVDF due to the surface-selective arrangement of MIL100-CS fillers which include both hydrophilic and biocidal properties. The live/dead test for antibacterial activities with E. coli cells further confirmed the enhanced suppression of the biofouling resistance in the asymmetric PVDF/MIL100-CS composite membranes relative to that of PVDF. Our current study offers a new platform for fabricating asymmetric MF composite membranes with enhanced antibacterial activity and biofouling resistance.