Dual superlyophobic zeolitic imidazolate framework-8 modified membrane for controllable oil/water emulsion separation

Abstract

The oil/water emulsion separation has become a thorny problem worldwide. Membrane separation based on superwetting materials has attracted immense attention in the domain of oil/water separation, while the single wettability severely limits their applications for treatment of different types oily wastewater. In this work, ZIF-8 modified membrane (RC@PDA/ZIF-8) is prepared via coordination-driven in situ self-assembly ZIF-8 on polydopamine (PDA) coated regenerated cellulose membrane (RC). The surface wettability of resultant membrane can be switched between underwater superoleophobicity and underoil (super)hydrophobicity by water or oils prewetted without additional external stimuli, which is suitable for controllable oil/water emulsion separation. Moreover, this membrane also displays superior separation capacity as high as above 99% and good flux for various oil-in-water and water-in-oil emulsions. Furthermore, the membrane shows good recyclability that it can retain high separation efficiency (98.5%) and flux after at least 10 times cycles. Also, the controllable emulsion separation mechanisms are analyzed and elucidated in detail. This ZIF-8 modified membrane with easy preparation and simple operation exhibits excellent separation efficiency and recyclability for controllable oil/water emulsion separation. Our work demonstrates MOFs-based membrane has potential applications including controllable oil/water separation and fuel purification.