RESUMO
Graphene-based membranes exhibit enormous potential in water desalination and purification because of their ultrathin structure, superhigh water flux, tunable physicochemical properties and precise ionic and molecular sieving performance. However, the transport behavior and mechanism of water, ions and other molecules across nanopores and nanocapillaries in the separation process, especially the confined mass transport, remain unclear, imposing severe limitation on many applications. Therefore, extensive experimental studies and theoretical calculation simulations have been carried out to investigate their unique structure and separation properties, particularly to explore the associated confined mass transport mechanism. Herein, an overview of the theory and simulation developments of graphene-based separation membranes based on confined mass transport is provided, attempting to open up an avenue for designing graphene-based materials as a new generation of separation membranes in the water purification field. This perspective focuses on five topics: (1) membrane transport models and simulation methods; (2) comparison between membrane simulations and experiments; (3) confined mass transport studies of graphene-based membranes with the assistance of molecular dynamics (MD) simulations; (4) fabrication of multifunctional composite membranes; and (5) future research trends in graphene-based membranes.
RESUMO
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.
RESUMO
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.
