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

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.