Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305-4020, USA.
Environ Sci Technol. 2010 Nov 1;44(21):8236-42. doi: 10.1021/es101601s.
The debromination of selected polybrominated diphenyl ethers (PBDEs) by nanoscale zerovalent iron particles (nZVI) was studied to investigate the degradation pathways and the reaction kinetics of the PBDEs. The primary PBDE investigated was 2,3,4-tribromodiphenyl ether (BDE 21) to assess degradation pathways. nZVI could effectively debrominate the selected PBDEs into lower brominated compounds and diphenyl ether, a completely debrominated form of PBDEs. The susceptibility of the meta-bromine by nZVI was observed from the debromination tests for PBDEs with single-flanked (2,3-diBDE and 3,4-diBDE) and unflanked (three mono-BDEs) bromines. The stepwise debromination from n-bromo- to (n-1)-bromodiphenyl ether was observed as the dominant reaction process, although simultaneous multistep debromination seemed to be plausible for di-BDEs having two bromines adjacent on the same phenyl ring. The reaction rate constants were estimated by assuming the reaction between PBDEs and nZVI was a pseudo-first-order reaction and the rates decreased with fewer bromine substituents. The reaction rate constants were correlated with the heat of formation and the energy of the lowest unoccupied molecular orbital of the corresponding compounds, and these appear to be useful descriptors of relative reaction rates among PBDE homologue groups.
研究了纳米零价铁颗粒（nZVI）对选定的多溴二苯醚（PBDEs）的脱溴反应，以探究 PBDEs 的降解途径和反应动力学。主要研究的 PBDE 是 2,3,4-三溴二苯醚（BDE 21），以评估降解途径。nZVI 可有效将选定的 PBDEs 脱溴为低溴化化合物和二苯醚，这是 PBDEs 的完全脱溴形式。通过对具有单侧（2,3-二溴和 3,4-二溴）和无侧链（三个单溴代二苯醚）溴的 PBDEs 的脱溴试验，观察到 nZVI 对间位溴的敏感性。观察到从 n-溴代到（n-1）-溴代二苯醚的逐步脱溴是主要的反应过程，尽管对于具有两个相邻在同一苯环上的溴的二溴代二苯醚，似乎同时进行多步脱溴是合理的。通过假设 PBDEs 与 nZVI 之间的反应是准一级反应，并随着溴取代基的减少而降低速率，来估算反应速率常数。反应速率常数与相应化合物的生成热和最低未占据分子轨道的能量相关联，这些似乎是 PBDE 同系物组之间相对反应速率的有用描述符。
