<br>水泥窑预分解炉中 BDE-209 热解形成自由基：模拟和 DFT 研究,Science of the Total Environment

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水泥窑预分解炉中 BDE-209 热解形成自由基：模拟和 DFT 研究
Science of the Total Environment ( IF 8.2 ) Pub Date : 2023-09-18 , DOI: 10.1016/j.scitotenv.2023.167145
Jinzhong Yang ₁ , Bo-Tao Zhang ₂ , Lu Tian ₃ , Qingqi Die ₃ , Fei Wang ₃ , Haihui Fu ₃ , Yufei Yang ₃ , Qifei Huang ₃

Affiliation

为深入了解含多溴二苯醚（PBDE）废物热处理过程中多溴二苯并对二恶英/呋喃（PBDD/Fs）的形成机理，本文研究了 PBDD/Fs 形成过程中关键中间体（自由基，FRs）的形成途径。以环境中最常见的 PBDE BDE-209 为研究对象，通过模拟温度（850 °C）和铁基等关键条件来分析 FR 的形成含 PBDE 的废物进入水泥窑预分解炉时的材料。采用电子顺磁共振（EPR）波谱和密度泛函理论（DFT）计算研究反应。模拟实验结果揭示了碳中心自由基，DMPO-OH 分析进一步证实了 FR 的产生。研究结果证实了先前的计算，预测在 BDE-209 形成 PBDD/Fs 过程中存在自由基中间体。DFT 计算显示 BDE-209 中存在内部正位 CBr 键。BDE-209 键断裂的优先顺序为乙键、内部正位 CBr 键和外部正位 CBr 键。BDE-209 还可以形成三种 FRs，即单苯环的氧心自由基、单苯环的碳心自由基和双苯环的碳心自由基。推断了 FR 形成的具体过程：高温均匀裂解化学键、电子转移和化学吸附，其中电子转移和化学吸附可能是更重要的途径。 BDE-209 中提出的内部正位切割为 PBDE 的降解和 PBDD/Fs 的形成提供了新的见解;关于 BDE-209 生成自由基的结果进一步阐明了二恶英的合成机制，这对于在处理和处置含 PBDE 的废物过程中控制二恶英的产生和排放非常重要。

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Free radical formation via BDE-209 thermolysis in the precalciner of a cement kiln: Simulation and DFT study

To deeply understand the formation mechanism of polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) in the thermal disposal process of polybrominated diphenyl ether (PBDE)-containing waste, this paper studied the formation pathways of key intermediates (free radicals, FRs) in the formation process of PBDD/Fs. BDE-209, the most common PBDE in the environment, was selected as the object of study to analyze FR formation by simulating the key conditions such as temperature (850 °C) and Fe-based materials when PBDE-containing waste entering cement kiln precalciner. Electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) calculations were used to study the reaction. The result of simulation experiments revealed carbon-centered radicals, and DMPO-OH analysis further confirmed the generation of FRs. The findings confirmed previous calculations predicting the existence of radical intermediates during the formation of PBDD/Fs from BDE-209. DFT calculations revealed the existence of an inner ortho-position CBr bond in BDE-209. The priority order of the bond breaking of BDE-209 was ether bond, inner ortho-position CBr bond, and outside ortho-position CBr bond. BDE-209 can further form three kinds of FRs, namely, oxygen-centered radicals of single benzene rings, carbon-centered radicals of single benzene rings, and carbon-centered radicals of double benzene rings. The specific processes of FR formation were inferred: high-temperature homogeneous cleavage of chemical bonds, electron transfer, and chemisorption, where electron transfer and chemisorption may be more important pathways. The proposed inner ortho-position cleavage within BDE-209 provides new insights into the degradation of PBDEs and the formation of PBDD/Fs; the results regarding BDE-209 generation radicals further elucidate the synthesis mechanism of dioxins, which is important for controlling dioxin generation and emission during the treatment and disposal of waste containing PBDEs.

更新日期：2023-09-18

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