Removal of dioxane pollutants from water by using Al-doped single walled carbon nanotubes

The detection and fast enrichment of toxic organic pollutants are challenging issues in the field of environmental science. We have studied the adsorption of dioxane on perfect, defected, and Al-doped CNTs by DFT calculations adopting the vdW forces corrections (vdW-DF). The accuracy of the vdW-DF results have been evaluated against the state-of-the-art B3LYP-D3 level of theory and it was shown that there is good agreement between the two respective methods. It was found that the dioxane adsorption ability of Al-CNT is much better (stronger) than perfect and defected CNTs. Calculations of the adsorption behavior of water molecules as a solvent demonstrate the existence of a stronger interaction between dioxane and Al-CNT in comparison with water molecules. Finally, we studied the interaction of dioxane molecules with CNT and Al-CNT in the presence of water molecules in ambient conditions using a DFTB-MD simulation. We showed that dioxane in the presence of water molecules is weakly bound (physisorption) to the outer surface of CNTs while it can be adsorbed on the Al-CNT system stronger than the water molecules as a competitor. Our study provides a molecular level understanding of the interactions between dioxane and CNTs and may be instructive for toxicity agent adsorption and detection from environment.