Preparation And Properties Of Guanidyl-functionalized Graphene/polysulfone Mixed Matrix Ultrafiltration Membranes

Ultrafiltration technology has received increased attention due to its numerous advantages and that has experienced rapid development over the past few decades.It has a relatively high removal rate for organic matter,bacteria and viruses.However,the membrane fouling problem existing in the actual application process has hindered its wide application.Graphene-based nanomaterials are regarded as a very promising nanomaterial for improving membrane properties owing to its superior hydrophilicity,mechanical stability and antibacterial propreties.At present,mixed matrix membranes prepared by blending a membrane matrix material with graphene-based nanomaterials exhibit great potential in water and wastewater treatment.In order to solve the complex biological pollution problems faced by ultrafiltration membranes in long-term use,a new synergistic antibacterial guanidyl-functionalized graphene/polysulfone?GFG/PSF?hybrid matrix ultrafiltration membrane was prepared by non-solvent induced phase separation method.The bacteriostasis of nanocomposites is explained by two aspects:partially reduced graphene oxide?GO?nanosheets with sharper edges to create a stronger interaction with the bacterial cell membrane to destroy the bacteria;the induced bidendate binding between guanidyl groups and phosphate groups on the cell wall can make high sterilization rate even at low concentrations.The guanidyl-functionalized graphene nanosheets are obtained by a two-step grafting process of amination and guanidination.The alkyl chain grafted by the amination modification process can be used as a soft segment to increase the flexibility of the guanidyl group,so that GFG and the PSF matrix can be better mixed.In this study,Fourier transform infrared spectroscopy?FTIR?,X-ray photoelectron spectroscopy?XPS?and other test methods were used to prove the successful preparation of GFG.The sedimentation experiment showed the high dispersibility of GFG in the casting solution,which solves the problem of poor dispersion of GO in organic solvent.Energy dispersive X-ray spectroscopy?EDX?test showed that the distribution of GFG on the surface of the membrane is relatively uniform,indicating the good compatibility between GFG and the polymer matrix.In addition,scanning electron microscopy?SEM?,contact angle tester,porosity and pore size test,permeation experiment,antifouling and antibacterial experiment were used to characterize and study the properties of different membranes.The results show that after the hydrophilic GFG nanosheets are mixed into the membrane,the pure water flux of the mixed matrix membrane is greatly increased.Compared with the pure PSF membrane,the maximum flux of the GFG/PSF-0.5 blend membrane increased to 217Lm^-2h^-1,which is about 2.2 times that of the pure PSF membrane.The GFG/PSF mixed matrix membranes not only exhibited excellent rejection to bovine serum albumin?BSA?and remarkable antifouling properties,but also shown excellent antibacterial activity and long-term antibacterial effect against Escherichia coli and Staphylococcus aureus.