Graphene Oxide Nanofiltration Membranes Containing Silver Nanoparticles: Tuning Separation Efficiency via Nanoparticle Size.

Three types of graphene oxide/silver nanoparticles (GO/AgNPs) composite membranes were prepared to investigate size-effect of AgNPs on nanofiltration ability. The size of AgNPs was 8, 20, and 33 nm, which was characterized by UV-visible spectroscopy and transmission electron microscopy. The morphology and structure of GO and GO/AgNPs composite membranes were characterized by atomic force microscopy, scanning electron microscopy, and X-ray diffraction. The filtration performance of membranes were evaluated on a dead-end filtration device. When the size of AgNPs is 20 nm, the GO/AgNPs composite membrane has the highest water flux (106.1 L m-2 h-1 bar-1) and rejection of Rhodamine B (RhB) (97.73%) among three types of composite membranes. The effect of feed concentration of dye solution and the flux of common solvent was also investigated. The mechanism was discussed, which demonstrated that both interlaying spacing and defect size influence the filtration ability of membrane, which is instructive to future study.

The Preparation and Study of Ethylene Glycol-Modified Graphene Oxide Membranes for Water Purification.

In this work, graphene oxide (GO)/ethylene glycol (EG) membranes were designed by a vacuum filtration method for molecular separation and water purification. The composite membranes were characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The interlayer spacing of GO membranes (0.825 nm) and GO/EG membranes (0.634 nm) are measured by X-ray diffraction (XRD). Using the vacuum filtration method, the membrane thickness can be controlled by selecting the volume of the solution from which the membrane is prepared, to achieve high water permeance and high rejection of Rhodamine B (RhB). The membrane performance was evaluated on a dead-end filtration device. The water permeance and rejection of RhB of the membranes are 103.35 L m-2 h-1 bar-1 and 94.56% (GO), 58.17 L m-2 h-1 bar-1 and 97.13% (GO/EG), respectively. The permeability of GO/EG membrane is about 40 × 10-6 L m-1 h-1 bar-1. Compared with the GO membrane, the GO/EG membrane has better separation performance because of its proper interlayer spacing. In this study, the highest rejection of RhB (99.92%) is achieved. The GO/EG membranes have potential applications in the fields of molecular separation and water purification.