The effect of functional group of Graphene-based woven filter on the desalination performance

Abstract

Abstract Graphene-based braided filter membranes (GWFM) are becoming increasingly crucial in seawater desalination because of their excellent performance, moving from research to practical use and helping to tackle water scarcity. However, the mechanisms associated with GWFMs functionalized by functional groups are unclear. This paper demonstrates that graphene strips are intricately integrated into a filtration membrane characterized by X-functional groups (GWFM-X). Molecular dynamics (MD) simulations are effective for calculating water flux, assessing salt discharge effects, and understanding the physical mechanisms in seawater desalination, making them crucial for optimizing and advancing desalination technology and salt rejection rate of four types of GWFM-X, namely GWFM-1.2nm-COOH, GWFM-1.2nm-NH2, GWFM-1nm-COOH, and GWFM-1nm-NH2, which were designed with different functional groups and nanopore diameters. These results demonstrate the superior performance of GWFM-X in water filtration applications. Salt rejection efficiency of four distinct variants of GWFM-X, namely GWFM-1.2nm-COOH, GWFM-1.2nm-NH2, GWFM-1nm-COOH, and GWFM-1nm-NH2, is designed with different functional groups and nanopore diameters. The test membrane shows exceptional water flux, significantly outperforming current commercial reverse osmosis membranes, with measurements of 30.00±0.49 L cm−2 day−1 MPa−1, 35.41±0.71 L cm−2 day−1 MPa−1, 9.31±0.31 L cm−2 day−1 MPa−1, and 20.66±0.21 L cm−2 day−1 MPa−1, respectively. The free energy profiles of GWFM-X reveal a pronounced disparity in free energy barriers between water molecules and Na+/Cl− ions, with a difference of up to 14.26 kBT. The simulation results show that the seawater desalination system maintains over 75% efficiency at pressures between 10 and 500 MPa, highlighting its effectiveness and versatility. Moreover, advancements in nanofabrication technology are paving the way for new membrane materials that could improve desalination methods and help address water scarcity.