Theoretical investigation of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin adsorption on pristine and iron‐modified carbon nanotubes

Abstract In this study, the adsorption of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) on pristine and Fe‐modified carbon nanotubes (CNTs) was investigated using the GFN2‐xTB method. The adsorption energy, structural parameters, and population analysis were computed to elucidate the nature of the adsorption forces. The results indicate that TCDD adsorption on pristine CNT is predominantly physical, driven by van der Waals interactions. In contrast, TCDD adsorption on Fe‐modified CNTs is identified as a chemical process, with covalent bonding occurring between Fe atoms and Cl atoms of TCDD, and no transition state being involved. The impact of varying Fe content and its distribution on CNTs was examined. It was found that increasing Fe content enhances the adsorption capacity, whereas Fe distribution on the CNT surface did not show a significant effect. The influence of different solvents—water, methanol, and benzene on the adsorption process was also evaluated. For physical adsorption, it was observed that the adsorption capacity decreases with increasing TCDD solubility in the solvent. However, for chemical adsorption on Fe‐CNTs, the effect of solvents was non‐monotonic, suggesting a complex interaction influenced by solvent properties.