Study On Superhydrophobic Modification Of Polypropylene Hollow Fiber Membrane

Currently, inspired by the self-cleaning and hydrophobic properties of lotus leaf, researchers have increasing interest in the basic theory and application of bionic superhydrophobic surface.Due to the advantages of non-wetting, self-cleaning and corrosion resistance, bionic superhydrophobic surface has been extensively applied in paints, building materials, bio-medicine. In this article, polypropylene hollow fiber membrane was used as the original matrix and modified to be a superhydrophobic material. The manufacturing processe of polypropylene hollow fiber membrane is mature and low-cost. However, its superhydrophobic modification process is more difficult compared to the flat membrane. The reports about the superhydrophobic modification of the polypropylene hollow fiber membrane is rare.In this article, a preparation method of superhydrophobic coating solution was offered, as the precursor, TEOS was hydrolyzed to the SiO2 ball, then was randomly copolymerized with the hydrolysate of MTES and the non-condensed TEOS. Then the SiO2 particle was fabricated and there was plenty of -CH3 groups on the surface which was the main reason of lower surface energy and contact angel higher than 160. Afterwards, the SiO2 particles and ethanol was added into the PVDF solution, the 3D network structure was prepared utilizing the method of phase separation. This fabrication method helped to build the structure of 3D network enhancing the toughness of the surface and immobilize the SiO2 particles on the surface, creating the superhydrophobic property. The method of surface coating on hollow fiber membrane raising the coating efficiency, therefore, the superhydrophobic property of hollow fiber membrane was improved and the contact angel was enhanced from 110° to 160°. The properties of material was characterized by measurement of contact angles、 FTIR、SEM. The influence of the concentration of MTES、PVDF、SiO2 and the coating times on the superhydrophobic property of material were discussed. The corrosive resistance was tested through dipping the modified hollow fiber membrane in the solutions of which the pH were 1-14.The superhydrophobic polypropylene hollow fiber membrane can be applied in the membrane distillation, the Vacuum Membrane Distillation was utilized to test the performance of the superhydrophobic membrane, the results showed that the flux of modified hollow fiber membrane dropped slightly, the retention rate improved significantly, up to 99.9% with a increased using longevity. Ultimately, the influence of water temperature、vacuum degree、brine rate、the concentration of water on the Vacuum Membrane Distillation were determined.