Catalytic Role of Palladium and Relative Reactivity of Substituted Chlorines during Adsorption and Treatment of PCBs on Reactive Activated Carbon
Catalytic Role of Palladium and Relative Reactivity of Substituted Chlorines during Adsorption and Treatment of PCBs on Reactive Activated Carbon
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DOI：
10.1021/es901298b
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发表时间：
2009-10-01
影响因子：
11.4
通讯作者：
Agarwal, Shirish
中科院分区：
文献类型：
--
作者：
Choi, Hyeok;Al-Abed, Souhail R.;Agarwal, Shirish
多氯联苯（PCBs）的吸附脱氯是活性炭（RAC）的一个独特功能。在这里，我们解决的RAC系统，含有一个可调量的Fe作为一个主要的电子供体加上钯作为电化学催化剂，以潜在的响应污染场地的特性，有效地陷阱和处理各种PCB同系物。RAC反应性的急剧增加与Pd掺杂低至0.01%表明其加速多氯联苯的加氢脱氯的关键作用。讨论了13种多氯联苯同系物的吸附脱氯特性及其在RAC表面的降解途径。重要的发现包括W固有的脱氯敏感性的氯在帕雷位> Meta位>邻位，无论独立或竞争条件以及基板的影响，（ii）有利的减少毒性更大的共面PCB同系物，（iii）优先亲电攻击氯在一个较少取代的苯环和一个孤立的氯，无论空间效应或诱导效应是邻位或Meta位多氯联苯脱氯的主要限制因素，（iv）对较高邻位同系物的脱氯抑制作用显著，但对较高Meta同系物的抑制作用可忽略不计，以及（v）高浓度多氯联苯同系物最终完全脱氯为联苯。
The adsorption-mediated dechlorination of polychlorinated biphenyls (PCBs) is a unique feature of reactive activated carbon (RAC). Here, we address the RAC system, containing a tunable amount of Fe as a primary electron donor coupled with Pd as an electrochemical catalyst to potentially respond to the characteristic of contaminated sites, effectively traps and treats various PCB congeners. A dramatic increase in RAC reactivity with Pd doping at as low as 0.01% suggests its critical role for accelerating hydrodechlorination of PCBs. Characteristic adsorption and dechlorination behavior and ensuing decomposition pathways of 13 selected PCB congeners are discussed with their surface interactions with RAC. Important findings include W inherent dechlorination susceptibility of chlorines in pare > meta > ortho position, regardless of independent or competitive conditions as well as substrate effects, (ii) favorable reduction of more toxic coplanar PCB congeners, (iii) preferential electrophilic attack to chlorines in a less substituted phenyl ring and an isolated chlorine, regardless of the steric or inductive effect as a dominant limiting factor for the dechlorination of ortho or meta PCBs, respectively, (iv) prominent dechlorination inhibition for higher ortho congeners but negligible inhibition for higher meta congeners, and (v) eventual complete dechlorination of higher PCB congeners to biphenyl.