Effect analysis on degradation mechanism of dioxins under hydrothermal conditions by molecular dynamic simulation

doi:10.1016/j.cjche.2024.12.004

Abstract

Abstract: The fly ash from waste incineration poses a serious threat to human health due to its high content of dioxins. Hydrothermal treatment is an efficient and clean method on the decomposition and detoxifying of fly ash. To study the degradation mechanism of dioxins, this paper uses molecular dynamics (MD) to simulate the hydrothermal reaction process of polychlorinated dibenzo-p-dioxins (PCDDs) under different conditions, and the degradation mechanism of PCDDs is obtained. The results show that the degradation of PCDDs includes two pathways: the first pathway is the substitution of Cl groups by hydroxyl groups to form low-chlorine substitution products through direct hydrogenation, and the second pathway is the formation of non-toxic benzene ring structures accompanied by the cleavage of C—O bonds. The two degradation pathways of PCDDs well explain the changes in toxicity before and after the hydrothermal treatment of fly ash, which is consistent with experimental results. This study provides theoretical guidance for the harmless treatment process of fly ash via hydrothermal method.

Key words: Fly ash, Dioxins, Hydrothermal reaction, Molecular dynamics method

摘要： The fly ash from waste incineration poses a serious threat to human health due to its high content of dioxins. Hydrothermal treatment is an efficient and clean method on the decomposition and detoxifying of fly ash. To study the degradation mechanism of dioxins, this paper uses molecular dynamics (MD) to simulate the hydrothermal reaction process of polychlorinated dibenzo-p-dioxins (PCDDs) under different conditions, and the degradation mechanism of PCDDs is obtained. The results show that the degradation of PCDDs includes two pathways: the first pathway is the substitution of Cl groups by hydroxyl groups to form low-chlorine substitution products through direct hydrogenation, and the second pathway is the formation of non-toxic benzene ring structures accompanied by the cleavage of C—O bonds. The two degradation pathways of PCDDs well explain the changes in toxicity before and after the hydrothermal treatment of fly ash, which is consistent with experimental results. This study provides theoretical guidance for the harmless treatment process of fly ash via hydrothermal method.

关键词: Fly ash, Dioxins, Hydrothermal reaction, Molecular dynamics method

Zhengyong Xu, Yan Du, Yan Liu, Jintao Ou, Jingwei Chen, Huaming Xie. Effect analysis on degradation mechanism of dioxins under hydrothermal conditions by molecular dynamic simulation[J]. Chinese Journal of Chemical Engineering, 2025, 80(4): 274-280.

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