Multilayer graphene with a rippled structure for water desalination

On the Choice of Different Water Model in Molecular Dynamics Simulations of Nanopore Transport Phenomena

The water transport through nanoporous multilayered graphene at 300k is investigated using molecular dynamics (MD) simulation with different water models in this study. We used functionalized and non-functionalized membranes along with five different 3-point rigid water models: SPC (simple point charge), SPC/E (extended simple point charge), TIP3P-FB (transferable intermolecular potential with 3 points-Force Balance), TIP3P-EW (transferable intermolecular potential with 3 points with Ewald summation) and OPC3 (3-point optimal point charge) water models. Based on our simulations with two water reservoirs and a porous multilayered graphene membrane in-between them, it is evident that the water transport varies significantly depending on the water model used, which is in good agreement with previous works. This study contributes to the selection of a water model for molecular dynamics simulations of water transport through multilayered porous graphene.

Novel adjustable monolayer carbon nitride membranes for high-performance saline water desalination

In this study, via molecular dynamic simulations, we showed that the latest described graphene-like carbon nitride membranes, such as g-C₄N₃, g-C₆N₆, and g-C₃N₄ single-layers, can be used as high-performance membranes for water desalination. In addition to having inherent nanopores and extraordinary mechanical properties, the carbon nitride membranes have high water permeability and strong ion rejection (IR) capability. The important point about carbon nitride membranes is that the open or closed state of the pores can be changed by applying tensile stress and creating a positive strain on the membrane. The effect of the imposed pressure, the tensile strain, the ion concentration, and the effective pore size of the membranes are reported. It is demonstrated that, with the applied tensile strain of 12%, the g-C₆N₆ membrane is the best purification membrane, with a water permeability of 54.16 l cm^-2 d^-1 MPa^-1 and the IR of 100%. Its water permeability is one order of magnitude greater than other one-atom-thick membranes.

Disinfection byproduct formation and toxicity of graphene oxide in water treatment system

Graphene oxide (GO) is a structural analog of graphene and contains numerous O-containing functional groups. As rapidly increasing production and usage of GO, it is inevitable to flow into the water and wastewater treatment system and finally oxidized by disinfectants to form DBPs. Meanwhile, as GO is a nano sized carbon material, it may also break the human digestion system when it was absorbed by human body. This study explored the DBP formation when only GO was present. Effects of Br^- were also considered during the DBP formation. Both trihalomethanes (THMs) and haloacetic acids (HAAs) were formed during the chlorination and chloramination procedure, but the total concentration of THMs was at least three times higher than that of HAAs. Irradiation can significantly enhance the DBP formation via the formation of radicals. The wrinkled appearance and decomposition of aromatic ring may both be effective on the DBP formation via chlorination or bromination. The findings of this study advance knowledge on the DBP formation of GO in water treatment systems and provide insight on the toxic effects of the transformation products of GO.