Manipulating F/O Ratio of Fluorinated Graphene Oxide to Improve Permeability and Antifouling Properties of Poly(vinylidene fluoride) Hybrid Membranes

Hybrid membranes blended with graphene oxide (GO) suffer from low modification efficiency due to the fact that plenty of GO are aggregated or embedded in the polymer matrix during the blending process. Herein, we designed different F/O ratios (R-F/O) of fluorinated graphene oxide (FGO) by plasma treatment (3, 5, 10, 15 and 20 min), and prepared novel poly(vinylidene fluoride)/FGO (PVDF/FGO) hybrid membranes via the phase inversion method. After a prolonged plasma treatment, the R-F/O of FGO was increased from 0 to 3.54 and the viscosity values of PVDF/FGO casting solution gradually improved, indicating the increasing dispersion of FGO with matrix. Moreover, water contact angle of membranes increased from 60.5 degrees (PVDF/GO) to 62.5 degrees (PVDF/FGO-10) (GO treated for 10 min, R-F/O = 1.35) and 67.5 degrees (PVDF/FGO-20, R-F/O = 3.54) because the migration ability of FGO, which contains a few oxygen-containing groups, decreased during phase inversion process. The dispersion and migration of FGO in membranes could be finely tailored by changing the R-F/O of FGO. As a result, water flux and flux recovery rate of PVDF/FGO (R-F/O = 1.35-1.7) (similar to 406.9 L.m(-2).h(-1) and similar to 88.9%) outperformed PVDF/GO (243.23 L.m(-2).h(-1) and 77.2%) and PVDF/FGO-20 membranes (266.9 L.m(-2).h(-1) and 71.7%). The bovine serum albumin rejection of modified membranes was still maintained above 80%, except PVDF/GO. Therefore, this study presented a novel strategy to reach the maximum performance of hybrid membranes via manipulating the ratio of hydrophilic and hydrophobic functional groups of nanomaterials to maintain moderately dispersion and migration ability in membranes.