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

CBET-0747735 Mitch本研究的目的是对在黑碳存在下卤化和硝化烃与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。使用模型疏水性持久性有机污染物（POP）和黑碳，不同的硫化物物种，黑碳官能团，和污染物取代基的重要性进行评估，通过还原和亲核取代途径的污染物破坏。这项研究将为开发一种对沉积物系统中的各种持久性有机污染物进行原位非生物销毁的技术奠定基础，这种技术应比目前的技术更便宜，对环境的破坏性也更小，有待检验的具体假设包括：1）与在没有黑碳的情况下进行的反应相比，在有硫化物存在的情况下，黑碳的存在将促进卤化和硝化有机物的降解。污染物吸附到黑碳上不会阻碍它们的破坏。2）在硫化氢存在下的破坏速率将与在多硫化物存在下的破坏速率相似，因为限速步骤将是黑碳中的活化醌型基团与有机污染物的反应，而不是硫化物对醌类化合物的活化。3）污染物破坏率将随着卤化或硝化的程度而增加，因为这些取代基的吸电子性质降低了最低未占分子轨道（ELUMO）的能量。还原将占主导地位的硝化和多卤代化合物，但亲核取代将成为重要的化合物与较少的卤素。测试上述三个主要假设的任务是：假设1 -反应性与黑碳性能的相关性假设2 -考试的相对重要性的二硫化物和多硫化物假设3 -相关性的反应性与污染物的取代基性能的工作将集中在基础实验室研究进行环境相关的条件下。本研究的发现将为未来的实地研究奠定基础。更多的理论水质控制类。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水力学项目，另一个是包含实验室组成部分的试验性工艺项目。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。 耶鲁大学的无国界工程师（EWB）分会已经启动，PI担任教员顾问。 EWB项目的小规模使学生能够在整个水系统上工作，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。设计类将纳入一个实际的EWB设计项目，最终在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.