Formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) by precursor pathways in oxidation of pesticide alpha-cypermethrin

Effect of NiFe2O4 on PCDF byproducts formation during thermal degradation of decachlorobiphenyl

“…As reported, polyaromatic hydrocarbons with biphenyl-like structures produce high amounts of PCDF and low amounts of PCDD. 16 Similar results were obtained in the oxidative process of pesticide a-cypermethrin at 300-650 C, 17 thermal treatment of model waste incinerator y ash in the presence of oxygenated-PAH (polyaromatic hydrocarbon) at 250-350 C, 18 and thermal treatment of sediments containing polychlorinated biphenyls. 19 The characteristic mid-ring structure of PCDD consists of a hexagonal ring bonded to two oxygen atoms, whereas that of PCDF consists of a pentagonal ring bonded to one oxygen atom.…”

“…Large R DF/DD ratios were also reported when PCDD/Fs were formed using biphenyl-like compounds as precursors. 16,17,19,49 Evaluation of the formation pathways of PCDD/Fs should therefore not only take into account the R DF/DD value, but also the reaction conditions and type of matrix.…”

“…Fullana et al 16 demonstrated that biphenyl and uorine can be easily converted into PCDFs at 300 C. Similar results were obtained in other studies that examined biphenyl-like compounds as precursors. 17,18 Zhao et al 19 reported that considerable amounts of PCDFs were formed when sediments containing polychlorinated biphenyls (PCBs) were subjected to thermal processes.…”

Gas Phase Thermal Oxidation of Endosulfan and Formation of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans

“…PCDD/Fs may be formed as byproducts in the manufacture and combustion of chlorinated pesticides or through incineration of municipal wastes and bushfires. , However, release of PCDD/Fs into the environment from pesticide use is poorly understood compared to other mechanisms. Although there does not appear to be any previous reports of emission of PCDD/Fs from endosulfan or related cyclodiene pesticides, our group has previously reported on the oxidation of chlorinated pesticides such as captan and alpha-cypermethrin, and we have postulated on the origin of PCDD/F emissions in terms of precursor pathways. , This study contributes to the calculation of PCDD/F emissions in thermal oxidation of endosulfan. Two distinct generic pathways have previously been proposed for production of PCDD/Fs in thermal processes.…”

Mechanism and thermal rate constants for complete series reactions of bromochlorophenols with H

“…Dioxins are formed via two general pathways: de novo synthesis and precursor pathways. Diversify precursors have been demonstrated, such as catechol, 28 captan pesticide, 29 polycyclic aromatic hydrocarbons (PAHs), 30 cypermethrin, 31 and polybrominated biphenyls. 32 Among various precursors, halogenated phenols are generally considered as the predominant precursors of dioxins and implicated as key intermediates in the de novo synthesis.…”