Adsorption Behavior\nof 2,3,7,8-Tetrachlorodibenzo‑<i>p</i>‑dioxin\nin Activated Carbon by Grand Canonical Monte\nCarlo: Effect of Pore Size and Distribution

Activated carbon with abundant nanoporous structures\ncan effectively\nadsorb 2,3,7,8-tetrachlorodibenzo-<i>p</i>-dioxin (TCDD)\nmolecules. However, an atomistic understanding of its underlying adsorption\nmechanism is still urgently needed because TCDD, given its strong\ntoxicity, requires strict testing conditions in experiments. In this\nwork, a series of grand canonical Monte Carlo (GCMC) simulations were\nperformed to evaluate the effects of the slit width and pore size\ndistribution (PSD) of activated carbons on TCDD adsorption. The microstructural\nanalyses of TCDD within nanoslits demonstrate that when the slit width\nexceeds 0.8 nm, the orientation of TCDD molecules inclines about 30°\nalong the axis’s normal direction, causing the adsorption amount\nto increase rapidly. When the slit width exceeds 2.0 nm, its disordered\norientation causes the adsorption amount to reach a maximum value.\nBased on this understanding, we determined the effective specific\npore volume (or effective specific surface area) for TCDD adsorption.\nIn combination with the full width at half-maximum (FWHM) of the PSD,\nwe propose the experimentally measurable structural parameter <i>V</i><sub><i>H></i>0.8</sub>/FWHM (or <i>S</i><sub><i>H></i>0.8</sub>/FWHM) and use it as an indicator\nto reflect the TCDD adsorption performance of different activated\ncarbons. A high structural parameter of activated carbon can indicate\na high TCDD adsorption amount.