Water desalination through charged graphene nanoslits: Role of edge chirality and electrostatic effects

XJ Xu and CC Lu and Y Zhang and SC Li and Y Yu and JH Zhao and N Wei, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 725, 137653 (2025).

DOI: 10.1016/j.colsurfa.2025.137653

Two-dimensional lamellar membranes, with nanoslits as key functional elements, hold significant promise for desalination applications. Optimizing the filtration performance of these nanoslits is essential for advancing desalination technologies. In this study, we systematically investigate the effects of chirality, charge distribution, and slit width on the desalination performance of graphene nanoslit membranes using molecular dynamic simulations. Our results reveal that increasing the absolute charge value (|q|) on armchair nanoslits enhances water permeation. For zigzag nanoslits, water permeation increases with decreasing negative charge (q < 0) but decreases once q drops below -0.4e. For positive charges (q > 0), both water permeation and salt rejection decrease as charge increases. Notably, the effect of charge distribution on water flux remains unaffected by slit size. The scalability of these findings is confirmed by evaluating the filtration performance of nanoslits in different two- dimensional materials, with results consistent with the prediction of charge distribution. We further analyze the thermal and dynamic properties of water in the nanoslit, including density maps, potential of mean force, hydrogen bond network, and diffusion coefficients, to better understand the water transport mechanism. Salt ion characteristics are also comprehensively examined. These findings suggest that modestly increasing charge density or incorporating negatively charge surfaces at the pore edges can significantly enhance reverse osmosis membrane performance, thereby advancing desalination technologies.

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