Enhanced water transport through a carbon nanotube controlled by the lateral pressure

Abstract

The transport of water through carbon nanotubes (CNTs) is now of great importance in bionanotechnology and of considerable interest for potential nanofluidic applications. In this paper, we show by molecular dynamics simulations that the permeation of single-file water molecules through a CNT can be significantly improved by means of tuning the direction of pressure difference, i.e. introducing an additional lateral pressure to the longitudinal one. The water flow exhibits an interesting maximum behavior with the change of lateral pressure, deciphered by the breakdown of single-file water chain inside the CNT. The translocation time decreases monotonously with the increase of lateral pressure and exhibits a clear bifurcation due to the longitudinal pressure, corresponding to the flow enhancement. Therefore, the lateral pressure will increase the difficulty for water entering, while promotes the water conduction inside the CNT, whose competition ultimately leads to the flow maximum behaviors. Along with the water reducing inside the CNT, the CNT switches between the filling and empty states with the unique distributions of water dipole orientation, density and H-bond number. Our results indicate that tuning the direction of pressure difference should be a significant new strategy for enhancing the water permeability, where the key lies in the breakdown of single-file water chain and are thus insightful for future studies.

Beyond the Pore Size Limitation of a Nanoporous Graphene Monolayer Membrane for Water Desalination Assisted by an External Electric Field

“…With growing demand for energy-efficient , water desalination, some schemes have been explored to enhance water permeability such as pore edges passivated with a chemical functional group, ,, a charged nanoporous graphene membrane, and polarized pore atoms . The enhancement of the transport of water through nanochannels by an axial electric field has also been extensively studied. − Recent developments of novel membranes mainly focus on improving water permeability rather than enhancing salt rejection. − Via oxygen plasma irradiation on monolayer graphene, the created membrane with nanopores (∼1 nm) exhibits high water flux but poor salt rejection . Because of the pore size limitation, solving the permeability–selectivity trade-off is still a challenge.…”

Flow through Deformed Carbon Nanotubes Predicted by Rigid and Flexible Water Models

“…For perfect zigzag nanotubes and large pressure gradients, the increase of pressure increases the flow . In the presence of any disturbance such as additional ions or asymmetric pressure, the behavior of the flow rate with pressure is monotonic. , This suggests that at small pressure gradients or in the presence of deformations, the flow rate is the result of a competition between the pressure and the local arrangements that attempt to make the water molecules form a single file.…”

Analysis of Mg2+/Li+ separation mechanism by charged nanofiltration membranes: visual simulation

“…Amir Razmjou et al [33,34] deeply investigated the effect of different nanochannels (surface charge, size, morphology and the driving force) on the separation of Li + ions from other ions. Currently, there are some reports on the theoretical prediction of NF membrane filtration and salt rejection, but their calculation process is complicated, abstract and difficult to understand [35][36][37][38]. Importantly, few reports have investigated how the charge capacity of the NF membranes can affect the separation performance of Mg 2+ and Li + quantitatively.…”