Influence of ultrasound on the adsorption of single-walled carbon nanotubes to phenol: A study by molecular dynamics simulation and experiment

Abstract

In this article, the effect of ultrasound on the adsorption of single-walled carbon nanotubes (SWNTs) to phenol was investigated by performing an all-atom molecular dynamics (MD) simulation. During the simulation process, a novel convenient method based on segmented simulation was proposed to realize the loading of ultrasonic boundary condition in MD simulation, which was realized by controlling the pressure changing as the positive and negative square wave. For evaluating the adsorption effect, structural parameters, interaction energies, hydrogen bond and number density distribution of water molecules were examined, and then an experiment was performed for verifying the conclusions of MD simulation. The results show that the external ultrasound can increase the amount of phenol around SWNTs, enhance the interaction energy between SWNTs and phenol molecules and weaken the hydrogen bond between phenol hydroxyl group and water molecules. These results indicate that the presence of ultrasound can promote the adsorption of carbon nanotubes to phenol. The experimental results for verification show that under ultrasound action, the concentration of the phenol solution is lower after adsorbed by SWNTs, which means that the adsorption of SWNTs to phenol has been promoted. In addition, the density distribution of water molecules decreases significantly only when the ultrasound generates negative pressure in the aqueous solution, which proves the correctness of the ultrasonic loading method proposed in this study.