Unveiling the promotional mechanisms of N-doping on the adsorption behaviors of dioxins from sintering flue gas by coconut shell-derived hierarchical porous carbon

Abstract

The heteroatom doping into the activated carbon (AC) has been proved to be one of powerful tools to remove dioxins from sintering flue gas. However, the fact that the intrinsic enhanced mechanism of specific nitrogen species still remains unanswered makes the choice and design of AC suitable for dioxins elimination difficult. Herein, nitrogen-doping AC with alterable N species were prepared by melamine modification to in-depth illuminate the promotional roles of N-containing groups on the adsorption of chlorobenzene (CB) (a model compound for dioxins) over ACs through experimental and density functional theory (DFT). The results demonstrated that the N-doping was obviously conducive to CB adsorption, and pyrrole N group with the strongest adsorption energy (−0.84 eV) between AC-pyrrole and CB was determined to be the key adsorption sites for CB. ACM600 with more pyrrole N group prominently improved the chemical adsorption of total adsorption amount from 8.18 % to 15.12 %. The adsorption mechanism of CB onto ACs was governed by physical adsorption and weak chemical adsorption, which was attributed to the synergistic effects of π-π stacking interaction and hydrogen bonds, and the π-π stacking interaction dominated the adsorption interactions. The introduction of heteroatom N enhanced the adsorption capacity by promoting the chemical reactivity and π-electron density distribution of AC, and forming more significant π-π stacking interaction with the π-acceptor. The study provided a sound theoretical guideline and scientific foundation for the design and estimation of carbonaceous materials for dioxins abatement.