title: Dissociative adsorption of 2,3,7,8-TCDD on the surfaces of typical metal oxides: a first-principles density functional theory study.
abstract: The initial dissociative adsorption step of the 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) molecule on the surfaces of MgO, CaO, and CuO has been studied by density functional theory (DFT) using periodic slab models. It is found that the 2,3,7,8-TCDD molecule undergoes a similar dissociative adsorption step during the decomposition over the three metal oxide surfaces. The adsorption configuration of 2,3,7,8-TCDD first converts from a parallel mode into a vertical one, then a nucleophilic substitution process takes place, where the surface oxygen atom attacks the aromatic carbon to form a surface phenolate with the chlorine atom moving to the top of the nearest surface metal atom. The calculated apparent activation energy of the dissociation increases in the order of CuO < CaO < MgO. The reaction heat is -0.67 eV, -0.75 eV, and 0.45 eV for CuO, CaO, and MgO, respectively, suggesting the thermodynamic tendency of MgO < CuO < CaO, which parallels the trend of the nucleophilicity of surface oxygen atoms. This study suggests that metal oxides with more nucleophilic and less tightly-bonded surface oxygen atoms might be more promising for the decomposition of polychlorinated dibenzo-p-dioxins and dibenzofurans.
authors: Key Laboratory of Environmental Pollution Process and Standard, Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China. maxd@nankai.edu.cn.
authors: Shuo
authors: S
authors: Zhao
authors: Xiaodong
authors: X
authors: Ma
authors: Qin
authors: Q
authors: Pang
authors: Hongwen
authors: H
authors: Sun
authors: Guichang
authors: G
authors: Wang
mesh_terms: D000327:Adsorption; D002248:Carbon Monoxide / Q000737:chemistry*; D002563:Cerium / Q000737:chemistry*; D008277:Magnesium Oxide / Q000737:chemistry*; D000072317:Polychlorinated Dibenzodioxins / Q000737:chemistry*; D011789:Quantum Theory; D013499:Surface Properties
chemical_list: D000072317:Polychlorinated Dibenzodioxins; D002563:Cerium; D008277:Magnesium Oxide; C030583:ceric oxide; D002248:Carbon Monoxide