Iron dependent oxidative remediation of chloethylenes

氯化乙烯是超级基金场址地下水中常见的一类环境污染物，已成为清理技术应用的目标。在不同的治疗方法中，依赖于氧化还原过程的原位抗生素修复有望成为一种有效且经济的替代“泵和处理”策略或依赖微生物的修复。原则上，氯化乙烯可以有效地脱氯为无害的碳质产物和无机氯化物，如果依次应用还原和氧化脱氯化学。随着引入由特定的零铁填充的可渗透反应处理壁，绿有机物的原位还原处理已经相当先进。还原性处理最适合于高氯化的氯乙烯类成员，目前需要氧化处理（空气喷射）的支持，以降解氯化程度较低的氯有机物和非氯化石油碳氢化合物。本提案研究了一种新的氧化方法，该方法依赖于氯乙烯的催化氧化/脱氯，在牺牲量的双氧和还原剂（通常是金属铁或锌）或过氧化氢存在下，由特定的铁试剂介导。这项工作的具体目标是：(i)开发铁基氧化系统，通过检查激活双氧或过氧化氢过程中相关铁配合物和中间体的基本化学成分，以解开攻击氯乙烯的活性氧化剂，从而在水介质中对氯乙烯进行氧化脱氯；（ii）通过检查所涉及的活性氧化剂的性质，通过中间体的光谱研究和动力学分析，以及通过探索这种氧化剂添加到氯乙烯中的方式（协同的，逐步的（自由基，碳阳离子）），提供脱氯过程的机理理解；（iii）探索在柱脱氯研究中与零价铁一起测试的铁试剂的异质版本。

Chlorinated ethylenes constitute a class of common environmental contaminants of groundwater at superfund sites that have been targeted fro application of cleanup technologies. Among different treatment methodologies, in situ antibiotic remediation that relies upon redox processes holds promise as an effective and economical alterative to "pump-and-treat" strategies or microbial-dependent remediation. In principle, chlorinated ethylenes can be efficiently dechlorinated to innocuous carbonaceous products and inorganic chloride, ir reductive and oxidative dechlorination chemistry is applied in sequence. In situ reductive treatment of chloroorganics has been considerably advanced with the introduction of permeable reactive treatment walls filled by particular zero-valiant iron. The reductive treatment is best suited for the highly-chlorinated members of the chloroethylene class and currently requires support by oxidative treatment (air sparging) to degrade less chlorinated chloroorganics and non-chlorinated petroleum hydrocarbons. The present proposal investigates a novel oxidative approach that relies upon catalytic oxygenation/dechlorination of chloroethylenes, mediated by specific iron regents in the presence of sacrificial amounts of dioxygen and a reducing agent (usually metallic Fe or Zn) or hydrogen peroxide alone. The specific targets of this work are to (i) develop iron-based oxidizing systems to perform oxidative dechlorination or chloroethylenes in aqueous media, by examining the fundamental chemistry of relevant iron complexes and intermediates in the course of activating dioxygen or hydrogen peroxide to unravel an active oxidant that attacks chloroethylenes; (ii) provide mechanistic understanding of the dechlorination process, by examining the nature of the active oxidant involved, via spectroscopic investigation of intermediates and kinetic analysis, and by exploring the manner by which this oxidant adds to chloroethylenes (concerted, step-wise (radical, carbocationic)); and (iii) explore heterogenized versions of the iron reagents to be tested in column dechlorination studies in conjunction with zero-valent iron.