Control one-dimensional length of rectangular pore on graphene membrane for better desalination performance

Abstract

At present, there is a general contradiction between permeability and selectivity of reverse osmosis (RO) membranes for desalination; a membrane with higher water permeability will give a lower salt rejection or selectivity, and vice versa. In this work, single-layer nanoporous graphene is used as RO membrane to investigate the effects of pore shape to reduce this contradiction by molecular dynamics (MD) simulations. Two kinds of pores (round and rectangular pores) with different sizes are simulated. For round pore, although the water permeability increases with the increase of the pore size, the salt rejection rate drops rapidly. For rectangular pore, reasonable designed pore structure can achieve improved water permeability and high salt rejection of graphene membrane by keeping one-dimensional length (i.e., the width) of the pore less than the size of the hydrated ions and increasing the other dimensional length. The restriction of one dimension can prevent the passage of hydrated ions through the pore effectively. This “one-dimensional restriction” provides a simple strategy for designing RO membrane with variable pore structures to obtain a better desalination performance.

Effect of Layer Orientation and Pore Morphology on Water Transport in Multilayered Porous Graphene

“…As mentioned earlier, we used two different pore shapes (circular and non-circular). As the transport of the water molecules varies based on the pore shapes [ 40 ], this is not a direct comparison between two pore shapes; rather, this study is aimed to get a better understanding of the variations of patterns and angles in both the circular and non-circular pore shapes.…”

Effective cross-linking strategy for graphene oxide membrane with high structural stability and enhanced separation performance

“…Compared with other wastewater treatment technologies, membrane separation is considered a promising method of wastewater treatment due to its unique benefits, which include low energy consumption, convenient operation, small occupied area and environment-friendly [1,2]. In recent years, graphene oxide (GO) has attracted great interest as a competitive candidate for use as a novel membrane material in wastewater treatment due to its low cost, simple fabrication, distinguished chemical stability, good hydrophilicity and unique sieving performance [3][4][5]. Foremost, unlike three-dimensional materials, GO nanosheet with a special two-dimensional lamellar structure and a thickness of less than 1 nm could be used to build an ultrathin GO membrane on various substrates via appropriate methods, including vacuum filtration, self-assembly, spraying and spin coating [6][7][8].…”