Study On The Modification Of PVDF Ultrafiltration Membranes By Grafting Amino-functionalized Graphere Oxide

In this study, we obtained the amine-functionalized graphene oxide (GO-NH2) by thedehydration condensation reaction between graphene oxide (GO) and ethylenediamine (EDA),which introduced amino (-NH2) groups onto the GO. Then the amine-functionalized GO sheetswere grafted onto the surface of polyvinylidene fluoride (PVDF) ultrafiltration membranes, withthe characteristics of dopamine (DOPA) such as self-assemble and chemical activity, presentingthe covalent bonds between the-NH2group and coated polydopamine layer. This modificationmethods improved the hydrophilicity and conduction of the UF membranessignificantly.Therefore,the paper focus on the preparation of GO-NH2and the characterization ofthe modified membranes.Utilizing the sheet structure of GO, it was formed a more dense graphitee separation layer on the surface of UF membranes. Thus, a more sophisticated filtering efficiencywas achieved by the grafted GO layer instead of the pristine membranes.The modified graphene oxide was prepared by the dehydration condensation reaction, and thesynthesized product was detected by fourier transform infrared spectroscopy (FTIR), thermalgravimetric analysis (TGA) and scanning electron microscopy (ESEM).The results indicated thatthe amino successfully grafted onto the GO sheets.We realized the surface modification of GO-garfting via the coated-DOPA on the PVDF membranes. Then the morphological and chemicalconstitution of the modified membrane surface were characterized by ESEM and FTIR, and thehydrophilicity and wettability were analysed via the contact angle measurement. The antifoulingability and stability of the modified membranes were investigated with oil/water emulsion, BSAand SA solution filtration tests.The results showed that both of pore size and porosity decreased, but the hydrophilicity and wettability was increased after the grafting modification. The hydrophilicity and wettabilityincreased with the increase of the GO concentration and grafting time of the grafing reaction,while the pure water flux improved firstly and then declined with the solvent concentration andgrafting time of the grafing reaction. The contact angle of the unmodified membrane is77°,decreased to61°after GO-NH2grafting. The pure water flux of PVDF UF membranes reducedfrom206.8L/(m2.h) to120.4(m2.h).The best grafting conditions is2mg/mL GO-NH2with thegrafting time60min in this investigtion.The antifouling and rejective ability of the modified membranes were investigated withoil/water emulsion, BSA and SA solution filtration tests. The experiment results showed that themodified membranes had a better antifouling and rejective ability. The stability was characterizedby the measurements of pure water flux and contact angle via soaking the membrane samples intoacid and alkali solution for a time. It was found that the modified membrane had a preferableresistance to acid solution, but poor to alkali solution. Moreover, the membranes fouled byoil/water emulsion were cleaned by1%surfactant solution at55?,the flux recovery of the graftedmembranes were above60%. Similar results were obtained in the fouling tests with BSA and SAsolution with1%NaOH solution cleaing at55?.