Molecular Dynamics of Benzoic Acid Adsorption on Carboxylated Carbon Nanotubes

We investigate, through molecular dynamics computer simulation, the adsorption behavior of single-walled carbon nanotube relative to degree of surface carboxylation. A model contaminant species in the form of benzoic acid is uniformly distributed in water creating a solution that is then allowed to adsorb on the tube. We control for tube chirality in two sets of starting systems. An iterative manual replacement of depleted regions was used to guarantee creation of at least one adsorption shell in each system. Aggregation trends in the adsorption shell reveal that uniformity of adsorption correlates well with amount of surface modification. We also assess the competitive adsorption between water and benzoic acid structurally by use of density, orientation, and hydrogen bonding analyses, and dynamically through diffusion calculations. Furthermore, limitations in the current simulation setup direct toward the usefulness of dissociation based analysis as gleaned from a corresponding experimental work that indicates charge-assisted hydrogen bonding might underlie an enhanced benzoic acid adsorption on carboxylated carbon nanotubes relative to the observed behavior on neat counterparts.