Surface functionalization via synergistic grafting of surface-modified silica nanoparticles and layered double hydroxide nanosheets for fabrication of superhydrophilic but relatively oleophobic antifouling membranes

Membrane fouling impedes the sustainable development of membrane-based separation technology. This study proposes a synergistic functionalization strategy via simultaneously tethering surface-modified SiO2 (M-SiO2) nanoparticles and layered double hydroxide (M-LDH) nanosheets to the membrane surface. A novel superhydrophilic but relatively oleophobic polyvinylidene fluoride membrane, which achieved a remarkable antifouling capability, was fabricated on the basis of this strategy. The synergistic functionalization with different nanomaterials brought about a heterogeneous and hierarchical membrane surface hence unique interfacial characteristics. The grafted spherical M-SiO2 nanoparticles and lamellar M-LDH nanosheets served as the superhydrophilic base and oleophobic barrier, respectively, thereby rendering the membrane surface superhydrophilic but relatively oleophobic. The functionalized membrane achieved an about 1.5 times higher permeability without loss of its selectivity as compared with the pristine membrane. Moreover, a series of ten-cycle fouling filtration tests were conducted with practical membrane bioreactor mixed liquor (containing activated sludge). As a result, the synergistic functionalization endowed the membrane with an up to 155% improvement in terms of flux recovery after cleaning, indicating a remarkable capability in resisting membrane fouling.