Preparation And Characterization Of Composite Nanofiltration Membrane Based On Interfacial Polymerization And Sol-gel Method

After more than half a century of development,nanofiltration membranes have been widely used in various fields and have achieved large-scale commercial production.The organic composite membrane prepared by interfacial polymerization method is currently the main product,but in practical applications,there are still many deficiencies such as poor fouling resistance,heat resistance and mechanical property.Therefore,it is of great significance to research and develop high-performance composite membrane through innovations of membrane materials and preparation technology.In this study,the composite nanofiltration membrane was prepared by interfacial polymerization coupled with sol-gel process,and the microstructure and separation performance of the separation layer obtained by interfacial polymerization were secondarily regulated by in-situ sol-gel to prepare high-performance composite nanofiltration membrane.Firstly,the nanofiltration membrane was prepared by interfacial polymerization and sol-gel method.Polyvinyl alcohol(PVA)and piperazine(PIP)were used as the monomers of aqueous phase,and trimesoyl chloride(TMC)and Tetraethyl orthosilicate(TEOS)were included in organic phase.Membrane with the separation layer containing TEOS was prepared by interfacial polymerization.Then the membrane structure and separation performance were modulated by sol-gel of TEOS.The effects of TEOS hydrolysis time and concentration,heat treatment temperature and time on microstructure and separation performance of nanofiltration membrane were systematically investigated.The appearance of new peaks of Si-O-Si and C-O-Si appear in infrared spectra and the increase of C/O and Si/O elemental ratios in the EDS spectra indicated the successful sol-gel of TEOS within the separation layer formed by interfacial polymerization and the chemical bonding with PVA.Compared with the nanofiltration membrane prepared by interfacial polymerization method with similar water flux,the Na2SO4 rejection increased from 75.8%to 91.4%,and the roughness decreased from 35.89 nm to 12.37 nm.Secondly,the separation performance of the composite membrane was comprehensively investigated.The results revealed that the desired membrane fabricated via method of interfacial polymerization and sol-gel possessed a molecular weight cut-off(MWCO)of 1130Da,corresponding to a pore radius of 0.84nm.The operating pressure of the nanofiltration membrane was positively correlated with the water flux,but had less effect on rejection.The feed concentration was negatively correlated with membrane flux and rejection.40-h continuous filtration demonstrated that the composite membrane prepared by the method of interfacial polymerization and sol-gel method possessed better performance stability.The removals of membrane to different dyes followed the order of R congored(99.9%)>Ralizarinyellow(99.5%)>R victoria blue B(98.3%)>R neutral red(72.3%).Finally,the anti-fouling performance of prepared membranes was investigated and compared.Compared to the membrane fabricated via interfacial polymerization with similar water permeability,the adsorption of bovine serum albumin(BSA)of the membrane fabricated via interfacial polymerization and sol-gel decreased from 66.32 ug/cm2 to 42.64 ug/cm2,the flux reduction ratio(RFR)decreased from 54.6%to 43.4%,the flux recovery ratio(FRR)increased from 67.4%to 81.7%and the total fouling ratio(Rt)declined from 50.3%to 41.9%,showing better anti-fouling property.