CAREER: Use of Black Carbon for the In-Situ, Abiotic Destruction of Sediment-Associated Persistent Organic Pollutants with Sulfides: A Combined Research and Educational Plan

本研究的目的是对黑碳存在下卤化和硝化碳氢化合物和硫化物之间发生的还原和亲核取代反应的性质有一个基本的了解。以模型疏水持久性有机污染物（POPs）和黑碳为研究对象，研究了不同硫化物种类、黑碳官能团和污染物取代基在还原和亲核取代途径中对污染物破坏的重要性。这项研究将为开发一种针对沉积物系统中各种持久性有机污染物的原位非生物破坏技术奠定基础，这种技术应该比目前的技术更便宜，对环境的破坏也更小。需要测试的具体假设包括：1)与没有黑碳的情况下进行的反应相比，在有硫化物的情况下，黑碳的存在会增强卤化和硝化有机物的降解。将污染物吸附到黑碳上不会妨碍它们的破坏。2)硫化氢存在时的破坏速率与多硫化物存在时的破坏速率相似，因为限速步骤将是黑碳中活化的类醌基团与有机污染物的反应，而不是硫化物对类醌的活化。3)随着卤化或硝化程度的增加，污染物的破坏速率会增加，因为这些取代基的吸电子性质降低了最低未占据分子轨道（ELUMO）的能量。对于硝化和多卤化化合物，还原将占主导地位，但对于卤素较少的化合物，亲核取代将变得重要。测试上述三个主要假设的任务是：假设1 -反应性与黑碳性质的相关性；假设2 -检查二硫化物和多硫化物的相对重要性；假设3 -反应性与污染物取代基性质的相关性工作将侧重于在环境相关条件下进行的基础实验室研究。本研究结果将为今后的实地研究奠定基础。对于本科生，将开设一门设计课程，以补充PI？这是一门理论性更强的水质控制课程。它将处理两个与发达国家有关的项目：一个是从当地一家咨询公司获得的液压项目，以及一个包含实验室组成部分的试点过程项目。该课程还将包括为发展中国家的一个村庄设计水处理系统。耶鲁大学已经成立了无国界工程师组织（EWB）分会，由PI担任指导教师。EWB项目的小规模使学生能够研究整个水系统，包括材料可用性等问题，以及通常控制基础设施项目的社会和政治背景。设计课程将包括一个实际的EWB设计项目，最后是一个可选的夏季安装之旅。

CBET- 0747735MitchThe objective of this research is to develop a fundamental understanding of the nature of the reduction and nucleophilic substitution reactions occurring between halogenated and nitrated hydrocarbons and sulfides in the presence of black carbons. Using model hydrophobic persistent organic pollutants (POPs) and black carbons, the importance of different sulfide species, black carbon functional groups, and contaminant substituents will be evaluated for contaminant destruction by reduction and nucleophilic substitution pathways. This research will lay the groundwork for the development of an in-situ, abiotic destruction technique for a wide range of POPs in sediment systems that should be less expensive and less environmentally disruptive than current techniques.Specific hypotheses to be tested include:1) The presence of black carbon will enhance the degradation of halogenated and nitrated organics in the presence of sulfides compared with reactions conducted in the absence of black carbons. Sorption of contaminants to black carbons will not hinder their destruction.2) Destruction rates in the presence of hydrogen sulfide will be similar to those in the presence of polysulfides, because the rate-limiting step will be the reaction of the activated quinoid groups in black carbons with the organic contaminant, not the activation of quinoids by sulfides.3) Contaminant destruction rates will increase with the extent of halogenation or nitration, as the electron-withdrawing nature of these substituents decreases the energy of the lowest unoccupied molecular orbital (ELUMO). Reductions will dominate for nitrated and polyhalogenated compounds, but nucleophilic substitutions will become important for compounds with fewer halogens.The tasks to test the above three main hypotheses are:Hypothesis 1 - Correlation of reactivity with black carbon propertiesHypothesis 2 - Examination of the relative importance of bisulfide and polysulfidesHypothesis 3 - Correlation of reactivity with contaminant substituent propertiesThe work will focus on fundamental laboratory studies conducted under environmentally-relevant conditions. Findings of this research will lay the groundwork for future field studies.For undergraduates, a design class will be developed to be complementary to the PI?s more theoretical Water Quality Control class. It will tackle two projects pertaining to the developed world: a hydraulics project obtained from a local consulting company, and a pilot process project incorporating a laboratory component. The class will also incorporate the design of a water treatment system for a village in the developing world. An Engineers without Borders (EWB) chapter at Yale has already been initiated, with the PI serving as the faculty advisor. The small size of EWB projects enables students to work on an entire water system, including issues such as material availability, and the social and political context that often controls infrastructure projects. The design class will incorporate an actual EWB design project, culminating in an optional summer installation trip.