Predicting adsorption of organic pollutants onto carbon nanomaterials (CNMs) and understanding the adsorption mechanisms are of great importance to assess the environmental behavior and ecological risks of both organic pollutants and CNMs. We computed the adsorption of cyclohexane, benzene derivatives, and polycyclic aromatic hydrocarbons (PAHs) on (8,0) single-walled carbon nanotubes by the M05-2X of density functional theory (DFT). Results show the computed adsorption energies (Ea) in the aqueous phase are lower than those in the gaseous phase, indicating that the adsorption in the aqueous phase is more favorable. The computed Gibbs free energy changes for the adsorption correlate significanty with the experimental values (r = 0.97, p &lt; 0.01). The contribution of π-π interactions and the enhancing effect of a −NO2 substituent on the adsorption were quantified. π-π interactions contribute about 24% of the total interactions as indicated by Ea. −NO2 enhances the π-π interactions due to its electron withdrawing effects, and contributes 24% to the value of Ea. To get an overall estimation on the contribution of different interactions, we further calculated the adsorption of 38 organic molecules (aliphatic hydrocarbons, benzene and its derivatives, and polycyclic aromatic hydrocarbons) onto pristine graphene in both gaseous and aqueous phases with DFT. Polyparameter linear free energy relationships (pp-LFERs) were developed for the adsorption energies. Based on the pp-LFERs, contributions of different interactions to the overall adsorption were estimated. The pp-LFERs indicate that the gaseous adsorption energies are mainly governed by dispersion and electrostatic interactions, while the aqueous adsorption energies are mainly determined by dispersion and hydrophobic interactions. It was also revealed that curvature of single-walled carbon nanotubes (SWNTs) exhibits more significant effects than the electronic properties (metallic or semiconducting) on gaseous adsorption energies, and graphene has stronger adsorption abilities than SWNTs. We also calculated the adsorption energies of C60 on relevant reference compounds of dissolved organic matter (DOM) and found the presence of DOM can increase the apparent water solubility of C60. The developed models may pave a promising way for predicting adsorption of environmental chemicals onto CNMs with in silico techniques.

Simulating and predicting adsorption of organic pollutants on carbon nanomaterials

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.