pH-Dependent thermoresponsive poly[2-(diethylamino)ethyl acrylamide]-grafted PVDF membranes with switchable wettability for efficient emulsion separation

Plenty of oily wastewater discharged from industrial and domestic sewage has deteriorated the environment severely, so stimuli-responsive membranes with switchable wettability have been of considerable attraction for its potential application in oil/water separation. In this work, a novel pH-dependent thermoresponsive membrane fabricated by grafting the poly[2-(diethylamino)ethyl acrylamide] (PDEAEAM) from the poly(vinylidene fluoride) (PVDF) membrane via surface-initiated atom transfer radical polymerization is explored to achieve the oil/water separation. The PDEAEAM- g -PVDF membrane shows hydrophilicity at room temperature under neutral condition while hydrophobicity at 50°C under alkaline condition. Wettability of the membrane at different temperatures is dominated by the lower critical solution temperature (LCST) of PDEAEAM, and the LCST of PDEAEAM is pH dependent. Due to the LCST of PDEAEAM, the membrane shows a variation of separation efficiency for separating hexadecane/water emulsion with temperature and pH. Typical separation efficiencies are 97.10% at 25°C under neutral condition and 30.26% at 50°C under alkaline condition.