| Nanofiltration?NF?is a kind of membrane separation process between ultrafiltration and reverse osmosis,which was developed on the basis of reverse osmosis in the 1980s,and has got rapid development in membrane technology.At present,interfacial polymerization is a more mature method for industrialized production of composite NF membranes.This paper added hydrophilic nanoparticles in polysulfone membrane for blending modification,then prepared composite NF membrane by interfacial polymerization.The primary tasks are as following:At first,the sol-gel process was used to prepare Ti O2 sol.Then the Ti O2 sol was added in the polysulfone?PSF?casting membrane solution to prepare polysulfone/Ti O2hybrid membrane by L-S phase inversion method.The effects of Ti O2 sol on PSF membrane's hydrophilicity,intercepting ability and porosity were studied.The rejection of bovine serum albumin?BSA,67000?represented intercepting ability.The water contact angle stood for hydrophilicity.Secondly,the polypiperazine-amide composite nanofiltration?NF?membranes were prepared on PSF/Ti O2 hybrid membranes by interfacial polymerization.Piperazine and trimesoyl chloride were used as monomers in aqueous phase and organic phase,respectively.Different preparation conditions affecting the separation performances of NF membrane were discussed,including piperazine concentration,trimesoyl chloride concentration,reaction time,heat treatment temperature and time.The chemical structure characterizations of polyamide composite membrane were tested by attenuated total reflectance infrared?FTIR?.The surface images and cross sections were observed by scanning electron microscope?SEM?and atomic force microscopy?AFM?.The results showed that the addition of Ti O2 sol changed the salt rejection slightly,but the water flux was three times than that of the polyamide membrane on the PSF support membrane.Polyamide NF membrane prepared under the optimum condition exhibited Na2SO4rejection of 96.94%and water flux of 12.84 L·m-2·h-1.According to the intercepting experiments of polyethylene glycols,the molecular weight cut-off?MWCO?of the resulting membrane was under 600 Da.In addition,the resulting composite nanofiltration membrane had good antifouling property,solvent resistance,acid resistance and high temperature resistant performance.Lastly,the prepared polyamide/Ti O2 composite NF membrane was applied to remove hexavalent chromium?Cr-VI?.The removal effect was good by means of changing p H of feed liquid,Cr concentration,etc.When p H was 8,the rejection of Cr-VI was over 98%.Because the composite layer has decisive impact on composite NF membrane separation performance,researchers always focus on the modification of composite layer to improve its hydrophilicity,antifouling property,thermal stability,etc.The research of blending modification of support membrane to increase the hydrophilicity is rarely reported.This study prepared a novel kind of polyamide/Ti O2 composite NF membrane with high water flux,high salt rejection and good removal of hexavalent chromium by interfacial polymerization on the basis of blending modification of PSF membrane. |
PDF Full Text Request