Plasma-Modified ZIF-8-Incorporated PVDF Membrane for Efficient Removal of Antibiotics from Water

To improve the performance of the polyvinylidene difluoride (PVDF) ultrafiltration membrane, a novel plasma-modified zeolitic imidazolate framework-8 (ZIF-8) filler was incorporated into it. This is the first time that defect engineering of a metal-organic framework filler with plasma modification is being explored in the case of water purification membranes. Through plasma modification, ZIF-8 developed metal deficiency, and that led to reorganization of the three-dimensional framework into a planar stacked one with increased surface charge. By virtue of adding the filler with surface charge, the hydrophilicity and porosity of the membrane were increased, as evidenced by water contact angle and scanning electron microscopy studies. Incorporating plasma-modified ZIF-8 into the PVDF matrix at optimum loading leads to a 43.05% increase in pure water flux, from 307.85 L/m² h to 432.56 L/m² h. The rejection rate for levofloxacin reached a maximum of 88.8%, while for ciprofloxacin, it was 79.3% in comparison to 73.60% and 58.47%, respectively, for the pure PVDF membrane. The probable mechanism of action was found to be increased hydrophilicity and dielectric repulsion from the membrane surface. This is by virtue of the induced beta phase increment due to repulsive interactions between the surface of the filler and the electron-rich C-F bond as understood through Fourier transform infrared spectroscopy and X-ray diffraction studies.