Triple-Layered Nanofibrous Metal–Organic Framework-Based Membranes for Desalination by Direct Contact Membrane Distillation

Water shortage is an emerging growing concern affecting the socio-economic viability of its victims. Varied fronts have been established to combat this problem with the intention of eradication. In this context, a triple-layered nanofibrous membrane consisting of (1) a nanofiber layer electrospun from poly(vinylidene fluoride) (PVDF) blended with hydrophobic SiO2 nanoparticles (NPs), (2) a nanofiber layer electrospun from polyacrylonitrile (PAN)/metal–organic frameworks (MOFs), and (3) a nanofiber layer electrospun from PVDF blended with hydrophilic SiO2 NPs is presented as the membrane for application in desalination by direct contact membrane distillation (DCMD). This novel membrane efficiently produced potable water that meets and surpasses drinking water standards in terms of conductivity. The membrane was characterized by scanning electron microscopy (SEM) and electron dispersive X-ray (EDX) spectroscopy, while the fillers were characterized by transmission electron microscopy (TEM). The electrospun nanofiber composite membrane with a 5 wt % hydrophobic SiO2–PVDF top layer, 1.5 wt % MOF–PAN middle layer, and 1 wt % hydrophilic SiO2–PVDF bottom layer exhibited the highest surface contact angle of 140.8° though the liquid entry pressure of water (LEPw) was relatively low (86.2 kPa). The membrane further exhibited a flux of 4.40 kg/m2h and permeate conductivity as low as 4 μS/cm during a 5 h operation with a transmembrane temperature difference of 30 °C and feed sodium chloride concentration of 35 g/L. The prepared composite nanofiber membranes are very stable in water and are suitable for use in producing pure water by desalination.