Simulation study on real laminar assembly of g-C3N4 high performance free standing membrane with bio-based materials

Abstract

The complex transport mechanism of water and ions in the membrane hinders the design of free standing membranes. The mechanism of the mass transport characteristics of traditional nanofiltration membranes is no longer applicable to free standing membranes due to the change of the driving force in the membrane. In this study, the vacuum filtration of the g-C3N4 suspension was simulated to form a free standing membrane model for the first time by using the molecular dynamics (MD) simulations. In the nanochannels formed by the g-C3N4 nanosheets, the water molecules rapidly penetrated across the free standing membrane due to ultra-low friction. On the other hand, the hydrated Na+ and Mg2+ ions needed energy to partially dehydrate and penetrate across the free standing membrane. Moreover, the MD simulations indicated that the speed of Mg2+ ions penetrating across the g-C3N4 nanochannels was lower than that of Na+ ions. Combined with the computational works, salt retention experiments were conducted to demonstrate the correctness of the proposed model. Further, the developed membranes exhibited excellent non-swelling stability and antibacterial activity in aqueous solutions. The g-C3N4 free standing membranes prepared in this study can effectively realize the separation of monovalent and divalent ions, accompanied with high permeability.