Effect of atomic ratio of ions on the particle diffusion and permeability of carbon nanotubes in reverse electrodialysis process using molecular dynamics simulation

Abstract

This study employed molecular dynamics simulations to investigate water transport through a carbon nanotube under an electric current, focusing on how varying ion atomic ratios influence key system parameters. These parameters include electric current intensity, fluid current intensity, maximum density, hydrogen bond count, and interaction energy as ion concentration changed. The research aimed to examine the effects of these changes on ion mobility, water permeability, and ion–carbon nanotube interactions. The study is conducted in two phases: equilibration, followed by the analysis of atomic transformations and the creation of various atomic ratios in samples. In the first phase, the kinetic energy of the atomic sample converges to 0.162 eV, and the potential energy reaches to 2.048 eV after 10 ns, indicating limited structural mobility and attractive forces among atoms. After equilibration, we achieved the atomic transformation process and created different atomic ratios. The results indicate that increasing ion ratios in the fluid led to a rise in electric current intensity, from 5.31 to 5.52 e/ns. Higher ion concentrations resulted in a greater density of charge carriers, enhancing ionic mobility and ion transport through the carbon nanotube. Moreover, higher ionic concentrations not only reduced the maximum density from 4.83 to 4.65 atoms/nm³ but also increases the number of broken hydrogen bonds, which could impact water transport and flow dynamics. Finally, according to the findings, there are 133 broken hydrogen bonds instead of 116, and the strength of the nanofluid flow, as well as the electric current, both increased when the ionic percentage of atoms rose to 5 %.