Superhydrophilic-underwater superoleophobic polyvinyl alcohol membranes for oily water treatment

Polyvinyl alcohol (PVA) and potato starch-based porous hydrogels have been fabricated and studied for their wettability. The starting material was crosslinked by glutaraldehyde performed via co-polymerization reaction at room temperature and low temperature (freeze–thaw). The gels were characterized by Fourier transform infrared (FT-IR), field emission scanning electron microscope (FE-SEM), thermogravimetric (TG), and powder X-ray diffraction (PXRD) analysis. The wetting studies of the gels were evaluated at ambient and submerged conditions by considering both oil and water drops as probe liquids. The gels tend to absorb oil and water in air, however, water-wet gels demonstrated a very high oil contact angle (>150°). The gels demonstrated superoleophobicity, and the underwater oil CA >172° as the concentration (wt%) of PVA was increased in the gels. Overall, the freeze–thaw gels demonstrated higher underwater oil CA, however, both (room temperature and freeze–thaw fabricated) gels demonstrated similar affinity for under-oil–water absorption and separation. The hydrogel can retain water easily and thus remove water (even dye dissolved in water) with high separation efficiency and recyclability.