Development of highly permeable and antifouling poly(vinylidene fluoride) hybrid membranes tailored with ZIF-8 metal-organic frameworks for water treatment

This study deals with the making of poly(vinylidene fluoride) (PVDF) hybrid ultrafiltration (UF) membranes incorporated with zeolitic imidazolate framework-8 (ZIF-8) nanocrystals. The surface morphology and roughness of ZIF-8 are explored in terms of atomic force microscopy (AFM) and scanning electron microscopy (SEM) whereas their distribution in PVDF matrix and antibacterial activity are probed by energy dispersive X-ray (EDX) analysis and zone of inhibition test. The chemical functionality of ZIF-8 is verified by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectroscopic studies. The permeability of hybrid membranes is raised to 2 wt% addition of ZIF-8 into the PVDF matrix owing to an enhancement in hydrophilicity and porosity. The FESEM images of the top and cross-section view make visible the formation of macrovoids with the addition of ZIF-8. On account of high porosity and surface hydrophilicity, the pure water permeation of hybrid membranes is increased to 278.6 Lm(-2) h(-1). The hybrid membranes showed higher rejection and permeate flux of bovine serum albumin (BSA; 92.8 Lm(-2) h(-1)) and humic acid (HA; 94.3 Lm(-2) h(-1)) owing to the synergetic effect of their enhanced hydrophilicity and surface roughness. This is confirmed by the higher flux recovery ratio (FRR) and lower irreversible fouling characteristics of hybrid PVDF membranes. The atomic absorption spectroscopy (AAS) revealed the long-standing stability of ZIF-8 in the PVDF matrix. Among all, the PVDF hybrid membrane with 2 wt% of ZIF-8 showed excellent permeability, antifouling, and antibiofouling ability and was found to be more effective in water treatment applications.