Strained single-layer C2N membrane for efficient seawater desalination via forward osmosis : a molecular dynamics study.

• Main Authors: Liu, Bo, Law, Adrian Wing-Keung, Zhou, Kun
• Other Authors: School of Civil and Environmental Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Environmental engineering; Seawater Desalination; C2N Membrane
• Online Access: https://hdl.handle.net/10356/141060
• Institution: Nanyang Technological University

Forward osmosis (FO) has proven to be a promising membrane separation technology for seawater desalination. However, advanced porous membranes are highly demanded to improve the efficiency of FO process. The single-layer C2N, also known as nitrogenated holey graphene, has recently emerged as a promising material for nanofiltration due to its intrinsic porous structure and robust mechanical strength. In this study, molecular dynamics simulations have been conducted to investigate the seawater desalination performance of the single-layer C2N membrane in the FO process by tuning its pore size using tensile strain. The results show that with a biaxial tensile strain larger than 4%, the C2N membrane becomes permeable to the water molecules but completely impermeable to the salt ions. At the strain of 12%, a water flux as high as 14.36 L cm−2 h−1 can be obtained at the moderate temperature of 338 K. Interestingly, the permeation water flux shows a nonmonotonic dependence on the osmosis pressure difference across the membrane. To understand the underlying mechanism, the potential mean force profile, water density distribution and hydrogen bonding dynamics are analyzed to investigate both the diffusion of the water molecules near the membrane and in the bulk salt solution. This study is helpful for the understanding of the water permeation behavior through the C2N membrane and promoting its application in seawater desalination.