Functionalized graphene oxide (f-GO) was synthesized by a simple covalent functionalization with 3-aminopropyltriethoxysilane (APTS). The hybrid polyvinylidene fluoride (PVDF) ultrafiltration membranes were then prepared by adding different ratios of graphene oxide (GO) and f-GO via phase inversion induced by immersion precipitation technique. Zeta potential demonstrated that covalent functionalization of GO with APTS was favorable for their homogeneous dispersion in organic solvents. SEM images showed that very large channel appeared in top-layer by the addition of additives. Furthermore, the PVDF/f-GO membranes exhibited superior hydrophilicity, water flux, BSA flux and rejection rate than nascent PVDF membranes and PVDF/GO membranes. Filtration results indicated that the fouling resistance parameters were significantly declined due to higher hydrophilicity of hybrid membranes. An atomic force microscope (AM) analysis with a BSA-immobilized Lip revealed that the adhesion forces between membrane and foulants increased in the following order: PVDF/f-GO < PVDF/GO < PVDF. After a ternary cycle BSA solution inner fouling process, PVDF/f-GO membranes exhibited higher water flux recovery ratio (ERR) value than that of PVDF/GO. Meanwhile, tensile strength and elongation-at-break of PVDF/f-GO membranes were increased by 69.01% and 48.38% compared with those of PVDF/GO membranes, which is believed to be attributed to the strong interfacial interaction between f-GO and matrix by covalent functionalization of GO. As a result, GO functionalization will provide a promising method to fabricate graphene-based hybrid membranes with effective reinforced permeation, antifouling and mechanical performance. (C) 2014 Elsevier B.V. All rights reserved,