Italicized carbon nanotube facilitating water transport: a molecular dynamics simulation

Abstract

While the preferential movement of water inside carbon nanotube is appealing for water purification, our understanding of the water transport mechanism through carbon nanotube (CNT)-based membrane is far from adequate. Here we conducted molecular dynamics simulations to study how the alignment of the CNTs in the membrane affects the water transport through the CNT membrane. It was shown that compared to the conventional CNT membrane where the alignment of CNTs was vertical to membrane surface, the “italicized CNT membrane” in which the contact angel between membrane surface and the CNT alignment is not 90° offered a higher transmembrane flux of water. The expanded exposure of more carbon atoms to water molecules reduced the energy barrier near the entrance of this italicized CNT membrane, compared to the vertical one. For water flows through the italicized CNT membrane, the Lennard-Jones interaction between water and nanotube as function of central path of the CNT changes from “U” to “V” pattern, which significantly lowers energy barrier for filling water into the CNT, favoring the water transport inside carbon nanotube. Above simulation indicates new opportunities for applying CNT in water purification or related fields in which water transport matters.