Amino Acids Functionalized Graphene Oxide for Enhanced Hydrophilicity and Antifouling Property of Poly(vinylidene fluoride) Membranes

Herein, functionalized graphene oxide（GO） was prepared by the covalent functionalization with amino acids（lysine, glycine, glutamic acid and tyrosine） in this study. Zeta potential results demonstrated that covalent functionalization of GO with amino acids was favourable for their homogeneous dispersion in water and organic solvents. Based on the higher absolute value of zeta potential and the better dipersion stability of GO-lysine, the PVDF/GO-lysine hybrid membranes were then prepared via the phase inversion induced by immersion precipitation technique. SEM images showed a better pore diameter and porosity distribution on the PVDF/GO-lysine membrane surface. The zeta potential absolute value of the PVDF/GO-lysine membrane surface was higher than that of the virgin PVDF membrane. Furthermore, the PVDF/GO-lysine membranes surface exhibited good hydrophilicity. The water flux of PVDF/GO-lysine membranes can reach two times of that of the virgin PVDF membrane. And the BSA adsorbed amount on PVDF/GO-lysine surface was decreased to 0.82 mg/cm^2 for PVDF/GO-lysine-8% membrane. Filtration experiment results indicated that the fouling resistance was significantly improved for the PVDF/GO-lysine membranes. As a result, lysine functionalized GO will provide a promising method to fabricate graphene oxide based hybrid membranes with effective antifouling property and hydrophilicity.

Excellent Hydrophilic and Anti-bacterial Fouling PVDF Membrane Based on Ag Nanoparticle Self-assembled PCBMA Polymer Brush

A silver nanoparticles-poly（carboxybetaine methacrylate） （AgNPs-PCBMA） nanocomposite was prepared on poly（vinylidene fluoride） （PVDF） membrane surface to improve its hydrophilicity and antifouling properties. Firstly, the PVDF membranes were grafted by PCBMA via physisorbed free radical grafting technique. Then Ag＋ coordinated to the carbonyl group on PCBMA and subsequently was reduced to silver nanoparticles. The hydrophilicity of the PVDF-g- PCBMA/Ag membrane was enhanced with the increasing fixed degree （FD） of AgNPs, and the original water contact angle of membrane was reduced to 33.97°. Additionally, water flux recovery ratio （FRR） and bovine serum albumin （BSA） rejection ratio of PVDF-g-PCBMA/AgNPs membrane were improved from 52% to 93.32% and 28.12% to 91.12%, respectively. Further, the PVDF-g-PCBMA/AgNPs membranes exhibited the more pronounced inhibition zone. The study demonstrated that compared with pure AgNPs or the PCBMA polymer brush, the synergistic effect of PCBMA and AgNPs made PVDF membranes have better hydrophilicity and anti-bacterial performances.