Efficient separation of O/W and W/O micro-emulsion by thermally responsive superantiwetting PVDF membrane

ABSTRACT Efficient separation of both oil-in-water (O/W) and water-in-oil (W/O) micro-emulsion was accomplished by a novel thermally responsive PVDF membrane. PNIPAAm–PVP–VTES micro-hydrogel was elaborately synthesized and incorporated into PVDF membrane, which was validated by transmission election microscopy (TEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transformed infrared spectroscopy (FTIR-ATR), laser confocal microscopy and thermogravimetric respectively. The thermally responsive mechanism of the engineered PVDF membrane was proposed from aspects of molecule structure, micro-hydrogel, membrane topology and membrane performance. The permeability and separation efficiency for pure water, both O/W and W/O micro-emulsions were modulated by temperature. The engineered PVDF membrane exhibited superantiwetting, outstanding permeability, high separation efficiency (>   99.90%), excellent antifouling property and reliability for long-term application. Moreover, multistage separation of oil-in-water micro-emulsion was achieved at nano-scale. Dispersed micro-emulsion droplets bigger than 20   nm and 40   nm were completely removed by manipulating the temperature below and above LCST , respectively. The engineered PVDF membrane highlights its great potential in micro-emulsion separation.