| Membrane distillation process is a high efficiency membrane separation process,which based on the hydrophobic microporous membrane as separation medium.In recent years,it has received widespread attention in the field of water treatment.Improving the hydrophobic of the membrane is the key factor to further improve the performance of membrane distillation.The immersion phase inversion method has broad application prospects in the preparation of hydrophobic membrane.So the membrane distillation performance would be improved greatly if the superhydrophobic membrane could be prepared by immersion phase inversion method.For the above objective,this study focused on the preparation of superhydrophobic membrane for membrane distillation.The main research contents and results as follows:The silica particle with different size was prepared by sol-gel method and added in PVDF dope solution in this paper.The PVDF flat sheet hydrophobic membrane was prepared by immersion phase inversion method.The hydrophobicity and flux of the membrane are enhanced greatly when the silica size is 251 nm,surface hydroxyl content is 0.94 mmol/g and concentration is 1.5 wt.%.The results showed that the contact angle of water reached 152.6° and the flux of membrane distillation reached 27.4 kg/(m2-h).The flux was 1.7 times higher and the stable operation time was 2 times than that membrane without silica.The interaction between silica and PVDF chains and the mechanism of silica in the phase inversion process were studied by XRD,FTIR and DSC methods.Hydrogen bond was formed between surface hydroxyl group of silica and PVDF,which induced the polymer crystallization.Then a superhydrophobic surface with micro-nano spherical structure was obtained on the bottom surface.At the same time,the earlier phase inversion process was accelerated by the surface hydroxyl of silica which increased hydrophilicity of dope solution,and the pore size and porosity increased. |
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