Effect of graphene oxide concentration on the morphologies and antifouling properties of PVDF ultrafiltration membranes

Poly (vinylidene fluoride) (PVDF)/graphene oxide (GO) ultrafiltration (UF) membranes are prepared via immersion precipitation phase inversion process. Raman spectra results indicate the existence of GO in PVDF/GO UF membranes. SEM pictures show that the PVDF/GO UF membranes present developed finger-like pore substructure along with the increased porosity and mean pore size. As revealed by FT-IR spectra, large amount of OH groups are appeared due to the introduction of GO nanosheets that improve the surface hydrophilicity of the modified membrane. In permeation experiment, the water flux is improved after blending GO. With 2 wt% GO content, the pure water flux and permeation flux reach peak values of 26.49 L/m2 h and 14.21 L/m2 h, increasing 79% and 99% respectively. Furthermore, the flux recovery ratio (FRR) and the fouling resistance results suggest that PVDF/GO UF membranes have better antifouling properties than pure PVDF due to the changes of surface hydrophilicity and membrane morphologies. AFM images show that UF membranes have a smoother surface with a higher efficient filtration area, which would enhance antifouling properties.