Evaluation of the physical properties and filtration efficiency of PVDF/PAN nanofiber membranes by using dry milk protein

Abstract

In engineering applications, especially ultrafiltration (UF) applications, it is very important to use polyacrylonitrile (PAN) and poly (vinylidene fluoride) (PVDF) nanofiber membranes. In this study, membrane nanofibers made of pure PAN, PVDF: PAN blends, and pure PVDF (M1, M2, M3, M4, M5, and M6), were produced by the electrospinning technique with different contents of PVDF in each blend. The prepared membranes were characterized by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), contact angle measurements, x-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrophotometry, and differential scanning calorimetry-thermogravimetric analysis (DSC-TGA). In terms of the physical properties, the viscosity of the membranes increased with an increase in the content of PVDF in the blends compared with the viscosity of the pure polymer solutions. This led to increases in nanofiber diameter, pore size, and porosity by 261.664%, 875.107%, and 114.41%, respectively, when the content of PVDF increased from 20% (M2) to 80% (M5); this was also accompanied by an increase in the surface wettability of the membrane depending on its contact angle. In addition, the thermal properties and crystallinity of PAN improved after increasing the PVDF content from 20% (M2) to 60% (M4). Moreover, the filtration efficiency of the membranes was measured to determine the per cent reduction in pure water flux, reduction in mean depth (RMD) before and after using dry milk protein, the flux recovery ratio and porosity, giving values of 15.68%, 82.51%, 84.32%, and 67.79%, respectively, for the M4 membrane.