Photodegradation of hexachlorobenzene and theoretical prediction of its degradation pathways using quantum chemical calculation

Yamada, Shingo; Naito, Yuta; Takada, Makoto; Nakai, Satoshi; Hosomi, Masaaki

doi:10.1016/j.chemosphere.2007.06.039

Cited by 40 publications

(24 citation statements)

References 12 publications

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“…The major hydrodechlorination pathways were determined by identifying the major intermediates at each stage of the process. 34 Thus, based on the amounts obtained for the detected PCN isomers, the predominant hydrodechlorination pathway of CN-75 on the prepared micro/nano Fe 3 O 4 likely involved CN-75 → CN-73 → CN-66/67 → CN-52/60---→CN-8/11, as highlighted in Scheme 1b. The degradation of CN-75 to CN-73 proceeded via elimination of a chlorine atom at one of the α-positions in CN-75.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Thermal Degradation of Octachloronaphthalene over As-Prepared Fe₃O₄ Micro/Nanomaterial and Its Hypothesized Mechanism

Lü

Zhang

et al. 2014

Environ. Sci. Technol.

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Decomposition of octachloronaphthalene (CN-75) featuring fully substituted chlorines was investigated over asprepared Fe 3 O 4 micro/nanomaterial at 300°C. It conforms to pseudo-first-order kinetics with k obs = 0.10 min −1 as comparable to that of hexachlorobenzene and decachlorobiphenyl. Analysis of the products indicates that the degradation of CN-75 proceeds via two competitive hydrodechlorination and oxidation pathways. The onset of hydrodechlorination producing lower chlorinated naphthalenes (CNs) is more favored on α-position than β-position. Higher amounts of CN-73, CN-66/67, CN-52/60, and CN-8/11 isomers were found, while small content difference was detected within the tetrachloronaphthalene and trichloronaphthalene homologues, which might be attributed to lower energy principle and steric effects. The important hydrodechlorination steps, leading to CN-73 ≫ CN-74 in two heptachloronaphthalene isomers contrary to that in technical PCN-mixtures, were specified by calculating the charge of natural bond orbitals in CN-75 and the energy of two heptachloronaphthalene radicals. On the basis of the molecular electrostatic potential of CN-75, the nucleophilic O 2− , and eletrophilic O 2 − and O − , present on the Fe 3 O 4 surface, might attack the carbon atom and π electron cloud of naphthalene ring, producing naphthol species with Mars−van Krevelen mechanism, and formic and acetic acids.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Thermal Degradation of Octachloronaphthalene over As-Prepared Fe₃O₄ Micro/Nanomaterial and Its Hypothesized Mechanism

Lü

Zhang

et al. 2014

Environ. Sci. Technol.

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“…5, the hydrodechlorination pathways diverged widely. The major hydrodechlorination pathways were determined by identifying the major intermediates at each stage of the hydrodechlorination process [41]. Based on the relative amounts of the PCB isomers detected (Table S3) The yields of the compounds depend on the rates of not only production but also consumption of these compounds.…”

Section: Activity Testmentioning

confidence: 99%

Degradation of polychlorinated biphenyls using mesoporous iron-based spinels

Huang¹,

Su²,

Zhang³

et al. 2013

Journal of Hazardous Materials

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h i g h l i g h t s• The NiFe 2 O 4 had the highest activity in degradation of CB-209, followed by Fe 3 O 4 .• Hydroxyl species, organic acids, PCBs and chlorobenzenes were identified as products.• Three degradation reactions and one combination reaction competitively occurred.• Hydrodechlorination of CB-209 was more favored over Fe 3 O 4 than NiFe 2 O 4 .• Oxidation reaction of CB-209 was more favored over t r a c tA series of mesoporous iron-based spinel materials were synthesized to degrade polychlorinated biphenyls (PCBs), with CB-209 being used as a model compound. The materials were characterized by X-ray powder diffraction (XRD), pore structure analysis, and X-ray photoelectron spectroscopy (XPS). A comparison of the dechlorination efficiencies (DEs) of the materials revealed that NiFe 2 O 4 had the highest DE, followed by Fe 3 O 4 . Newly produced polychlorinated biphenyls, chlorinated benzenes, hydroxyl species and organic acids were detected by gas chromatography-mass spectrometry, high performance liquid chromatography-mass spectrometry and ion chromatograph. Identification of the intermediate products indicates that three degradation pathways, hydrodechlorination, the breakage of C C bridge bond and oxidative reaction, accompanied by one combination reaction, are competitively occurring over the iron-based spinels. The relative amounts of produced three NoCB isomers were illustrated by the C Cl BDEs of CB-209 at meta-, para-and ortho-positions, and their energy gap between HOMO and LUMO. The consumption of the reactive oxygen species caused by the transformation of Fe 3 O 4 into Fe 2 O 3 in the Fe 3 O 4 reaction system, and the existence of the highly reactive O 2 −• species in the NiFe 2 O 4 reaction system, could provide a reason why the oxidation reaction was more favored over NiFe 2 O 4 than Fe 3 O 4 .

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“…Because of the extremely low water solubility, HCB photodechlorination were mainly conducted in organic solvent or surfactant solutions [85][86][87]. In addition, organic solvent and surfactants are also washing agents for HCB remediation, and the washing liquid dissolving HCB need further treatment.…”

Section: Photodechlorination Of Hcbmentioning

confidence: 99%

Physiochemical technologies for HCB remediation and disposal: A review

Tong

Yuan

2012

Journal of Hazardous Materials

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Photodegradation of hexachlorobenzene and theoretical prediction of its degradation pathways using quantum chemical calculation

Cited by 40 publications

References 12 publications

Thermal Degradation of Octachloronaphthalene over As-Prepared Fe₃O₄ Micro/Nanomaterial and Its Hypothesized Mechanism

Thermal Degradation of Octachloronaphthalene over As-Prepared Fe₃O₄ Micro/Nanomaterial and Its Hypothesized Mechanism

Degradation of polychlorinated biphenyls using mesoporous iron-based spinels

Physiochemical technologies for HCB remediation and disposal: A review

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Photodegradation of hexachlorobenzene and theoretical prediction of its degradation pathways using quantum chemical calculation

Cited by 40 publications

References 12 publications

Thermal Degradation of Octachloronaphthalene over As-Prepared Fe3O4 Micro/Nanomaterial and Its Hypothesized Mechanism

Thermal Degradation of Octachloronaphthalene over As-Prepared Fe3O4 Micro/Nanomaterial and Its Hypothesized Mechanism

Degradation of polychlorinated biphenyls using mesoporous iron-based spinels

Physiochemical technologies for HCB remediation and disposal: A review

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Thermal Degradation of Octachloronaphthalene over As-Prepared Fe₃O₄ Micro/Nanomaterial and Its Hypothesized Mechanism

Thermal Degradation of Octachloronaphthalene over As-Prepared Fe₃O₄ Micro/Nanomaterial and Its Hypothesized Mechanism