The Modification And Functionalization Of Polymer Separation Membranes Based On Grahene Oxide And Its Composites

The main research of this dissertation focused on the hydrophilic modification and functionalization of polyether sulfone(PES)and poly(vinylidene fluoride)(PVDF)membranes.PES and PVDF have been widely used in microfiltration and ultrafiltration field for decades.However,there are some limitations,such as low permeation flux and protein fouling due to the hydrophobic property.According to previous research,the surface hydrophilization modification of PES and PVDF porous membranes is considered to be an effective way to enhance the permeability and antifouling resistance of protein.In this paper,the PES and PVDF membranes were hydrophilic modification and functionalization by graphene oxide by blending or self-assembly methods,and the structure and properties such as hydrophilicity,antifouling resistance,antibacterial performance of the modified polymer separation membranes were sysmatically investigated in this paper.The main contents are summarized as following:(1)The graphene oxide(GO)was prepared by Improved Hummers method.And then the structure and chemical composition of GO was characterized by XRD,FTIR.The results proved that the there was abundant hydroxyl,carboxyl and epoxy reactive functional groups on GO surface.Then GO was blended with PES to fabricate the sulfone/graphene oxide(PES/GO)blend membranes via immersion precipitation phase inversion process.And the effect of GO on membranes structure,hydrophilicity,antifouling resistance,and heavy metals and organic dye adsorption performance was systematically explored.The investigation results demonstrated that the hydrophilicity and mechanical properties of the PES/GO membranes were superior to the virgin PES membrane.In addition,BSA static adsorption experiment proved that the PES/GO blend membranes had good protein pollution resistance.At the same time,the heavy metals and organic dye adsorption experiments showed that PES/GO blend membranes had a good adsorption performance of Pb(II),Cr(VI)and methylene blue.Especially removal rate for heavy metal Pb(II)can reach 93.2%,which was far higher than that of PES membrane.(2)The GO-amino acids polymer was successfully synthsised via the condensation reaction between GO and amino acid(lysine,glycine,glutamic acid and tyrosine).TGA,Zeta potential measurement showed that the dispersion stability of GO-lysine polymer was better than that of others.Then the PVDF/GO-lysine membranes were prepared via immersion precipitation phase inverision process with the GO-Iysine polymer as additive.Results demonstrated that the GO-lysine polymer was mainly located on membrane surface and impart the membranes with good hydrophilicity.For instance,the initial contact angle of the blend membrane was decreased to 75°from the 102° of virgin PVDF membrane.Especially,when the weight ratio of GO-lysine in blend membrane was 8%,the contact angle was down to 15° within 6 s.BSA static adsorption experiment and filtering experiment results showed that the PVDF/GO-lysine blend membrane showed good permeability and antifouling resistance.(3)The PVDF membranes were surface modified dopamine(DPA),and then the GO was self-assembly on membrane surface.After that,silver nanoparticles(AgNPS)were immobilized on the surface with the coordination of Ag+ and-COO-obtain the Ag/PVDF-GO membranes.The surface composition and chemical structure was determined with XPS.The SEM characterization showed that the silver nanoparticles was distributed on membrane surface uniformly,and the particle size was around 50-100 nm.The hydrophilicity of PVDF-GO and Ag/PVDF-GO membranes was better than the original PVDF membrane obviously.The bacteriostatic experiment indicated that silver particles can effectively improve the ability of the inhibit bacterial contamination of membrane.And along with the increase of the silver particles on membrane surface,the antibacterial performance got stronger.