Fabrication of highly hydrophobic or superhydrophobic electrospun PVA and agar/PVA membrane materials for efficient and selective oil/water separation

Efficient and selective separation of oily substances from water or oil-water emulsions is a very important issue in the treatment processes of oily wastewater to prevent environmental pollution. In this study, for the effective treatment of water polluted with oils or organic solvents, highly hydrophobic or superhydrophobic water-insoluble eco-friendly electrospun poly(vinyl alcohol) (PVA) and agar/PVA membrane materials were successfully prepared via (i) electrospinning technique, (ii) cross-linking approach with glutaraldehyde and (iii) coating process with methyltrichlorosilane (MTCS) in petroleum ether. Membrane materials were characterized with contact angle, water solubility, FT-IR, SEM and XPS measurements. Water contact angle (WCA) of PVA and agar/PVA membranes was measured as 148.1° and 150.1°, respectively. Membrane materials were able to separate selectively the toluene and chloroform droplets from water and showed good oil and organic solvent absorption capacity (5.5–22.8 g g−1 for PVA membrane and 4.1–21.7 g g−1 for agar/PVA membrane). For chloroform-water mixture (1:1, v/v), the flux value of PVA and agar/PVA membranes was determined to be 1234 L m−2 h−1 bar−1 and 1136 L m−2 h−1 bar−1, respectively. In addition, the developed membrane materials displayed excellent separation efficiency (≥99.9%) for chloroform-water mixture. PVA and agar/PVA membranes exhibited a good water-in-oil/organic solvent (water-in-toluene, water-in-chloroform and water-in-diesel) emulsion separation performance (≥97.5%). PVA and agar/PVA membrane materials prepared in this study are environmentally friendly and have an affordable price and the potential in practical applications for the treatment of wastewater polluted with oils and organic solvents and for the separation of oily substance-water mixtures.