A large amount of oily wastewater is produced every day during industrial processes,such as petrochemical,daily chemical,leather,textile and steel processes,which caused increasingly serious environmental pollution.In addition,with the everincreasing growth of population and urbanization,freshwater scarcity has become another severe problem in the world especially in water-stressed areas.Recycling the oily wastewater could reduce the environmental pollution and increase the available water supply.Therefore,it is of great significance to develop a highly energy-efficient and broadly applicable approach for effective separation of oil-water mixtures.This study focuses on optimizating the structure of PVDF membrane and improving the separation and antifouling performance of PVDF membrane for the separation of oilwater emulsions.The details are listed as follows:First,this study developed the regulation of preparation conditions on the structure and performance of PVDF membrane via immersion precipitation method.Solvents,pore-forming agent,the concentration of PVDF and the addition of HNTs have been investigated through the analysis of the microstructure of cross sections,the separation performance and the hydrophilicity of PVDF membrane.With the focus of the kind of solvents,it was found that the morphologies and separation performance of PVDF membranes were correlated closely with the solubility parameters of the cast solution.And PVP played an siginificant role in improving the morphologies and separation performance of PVDF membranes.Besides,with the increasing of the concentration of PVDF in casting solution,the average pore size,porosity and pure water flux decreased gradually.The studies of the effect of HNTs showed that the hydrophilicity of PVDF membrane was improved apparently.Second,ILHNTs-PVDF hybrid membranes were fabricated by the addition of room-temperature ionic liquids grafted halloysite nanotubes,aiming at improving the separation and antifouling performance of PVDF membrane further.Herein,HNTs were first functionalized by one-step grafting with 1-methyl-3-(3-triethoxysilypropyl)imidazolium chloride(IL).Fourier transform infrared spectrometer(FTIR),thermogravimetric analysis(TGA)and transmission electron microscopy(TEM)indicated that HNTs had been grafted by room-temperature ionic liquids successfully.Afterwards,the effects of ILHNTs on the morphology,hydrophilicity,filtration and antifouling performance of PVDF membranes were investigated systematically.It can be concluded that the addition of ILHNTs effectively solve the problems of the aggregation and poor dispersion of HNTs in membrane matrix.Besides,ILHNTs enhanced the hydrophilicity and permeability of PVDF membranes,endowing the membranes with better separation and antifouling performance.Tensile test confirmed that PVDF membrane exhibited better mechanical properties with the addition of ILHNTs.Finally,the prepared hybrid PVDF membranes were assessed by the separation of oil-water emulsions.The separation experiments of diesel,petroleum ether,soybean oil,gasoline and n-hexane oil-water emulsions indicated that the membranes exhibited high rejection ratios(RR)when ILHNTs were incorporated.The resistence test implyed that the modified PVDF membranes had a good resistance ability to the diesel oil-water emulsions.In conclusion,ILHNTs play a significant role in improving the separation and antifouling performance of PVDF membranes for oil-water separation. |