Preparation Of New Flexible Organosilicon Composite Films And Their Dehydration Properties With Isopropanol

Bridged organic-inorganic hybrid silica(refers to organosilica)materials are usually prepared via sol-gel hydrolysis and condensation with the bridged sesquisiloxane as silica source precursor.Owing to excellent thermal stability,adjustable pore size and surface properties,they were usually applied to the gas separation,reverse osmosis desalination,pervaporation dehydration and the separation of organic solvents.However,almost all of these organosilica membranes are prepared on flat or tubular inorganic supports such as Al₂O₃,which limits the applications of them due to the high cost of the support materials and complex fabrication processes,which results in scale-up difficulties.To overcome these potential disadvantages,a new approach to the application of organosilica layers using a relatively low-cost polymeric support was proposed.In this work,using 1,2-bis(triethoxysilyl)ethane(BTESE)as a precursor,a continuous and defect-free BTESE separation layer was deposited onto the surface of a polymeric nanofiltration membrane via a facile,reproducible and scalable sol–gel spray coating followed by the heat-treatment process.The experimental results show that the structure and properties of the hybrid silica membranes can be effectively controlled by adjusting the membrane preparation conditions such as solvent type,sol concentration,spraying spacing and spraying amplitude,and finally the polymer-supported flexible organosilica hybrid membrane with high performance can be obtained.The surface characteristics,thickness distribution,membrane structure and properties of flexible organosilica composite membranes were characterized and analyzed by means of field emission scanning electron microscope(SEM),contact Angle tester,atomic force microscope(AFM),gas chromatograph and ellipsometer(SE).The major research focuses on the following:(1)Preparation and characterization of dense polysulfone supported flexible organosilica composite filmsThe dense polysulfone supported flexible organosilica composite thin film was successfully prepared by sol-gel spray coating method.First,the coating conditions were explored by means of ink staining experiment,and then the affinity behavior of BTESE organosilica sol on the surface of polysulfone film and the change relationship between the concentration of BTESE sol and the thickness of BTESE coating were explored.Through ink dyeing experiment and other methods,the conditions of spray coating were determined:spraying height of 12 cm,spray spacing of 16.7 mm,flow rate of 0.1 m L/s,nozzle moving speed of 100 mm/s,ambient(15?20?).Under the joint influence of solvent evaporation rate and Marnagoni effect,the good homogeneity of PSF-BTESE thin film was obtained when using isopropanol or n-propanol as the solvent.(2)Preparation and isopropanol dehydration performance of porous polysulfone supported flexible organosilica composite membranesIn this section,we reported a facile and technologically scalable approach for the fabrication of flexible organosilica membranes,where a thin and uniform organosilica active layer was deposited onto porous commercialized polymeric nanofiltration membranes(NTR series:NTR7410)via the sol-gel spray coating process with a single-pass method.Firstly,the optimal deposition conditions were investigated and established,including sol concentrations and the type of the alcoholic solvent which is used to prepare organosilica sol.SEM and the spectra of both XPS and FTIR confirmed that a BTESE-derived organosilica layer was successfully formed on NTR surface,thus-produced flexible organosilica membranes exhibited superior dehydration performance of isopropanol/water solutions(IPA:90 wt%)in the vapor permeation process,and show a high water flux(4.0 kg/(m² h))and a separation factor of about 1000.