Molecular insight into water desalination mechanism through g-C3N4 nano- slit membranes: Effect of slit sizes, terminal groups, and number of layers

MR Madhoush and MH Sarrafzadeh and A Hosseinian, JOURNAL OF MOLECULAR LIQUIDS, 392, 123532 (2023).

DOI: 10.1016/j.molliq.2023.123532

Among all novel 2D materials used for membrane separation, graphitic carbon nitride (g-C3N4) has gained more attention in recent years because of its catalytic activity. Density functional theory has revealed that there are three or two types of nitrogen and carbon atoms based on their partial charges in the g-C3N4 structure, which are assumed to interact with water differently. This work used classical molecular dynamics (MD) to elucidate how these different edge atoms interact with water molecules and ions. Results indicated that nitrogen- terminated membranes were superior in all cases, but increasing slit size resulted in independency of water flux from the terminal atoms type. The significant permeability of nitrogen-terminated membranes was ascribed to hydrogen bonding between water and nitrogen atoms, which was proved through various analyses. It also revealed that the more partial charges on some nitrogen atoms attract more water molecules and facile water transport by reducing the energy barrier. These partial charges also affect ions passing based on their charges. Besides this, adding just one layer of g-C3N4 in multilayered membranes could improve salt rejection significantly but lead to a significant decrease in permeability. Briefly, this work proved that g-C3N4 nano-slits have great potential to be utilized as membrane material. In addition, it revealed the water and ions transport mechanism through the nano-slits, which could give more details to proper g-C3N4 membrane design.

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