CAREER: Formation and Reactivity of Nanoscale Corrosion Products - An Integrated Research and Education Plan

维克斯兰职业发展计划分为两个主要部分：一项研究计划描述了检查纳米级腐蚀产物的形成和反应性的实验，另一项教学计划旨在重振弗吉尼亚理工大学环境工程导论课程的教学环境。该项目的目标是评估纳米级腐蚀产品在确定用于修复受有机卤化物污染的地下环境的颗粒铁处理方案的反应性方面所起的作用。拟议研究的结果将用于开发一个改进的概念模型，说明颗粒铁系统内负责污染物修复的现象。利用铁腐蚀修复受污染的地下水发现，氯化溶剂很容易与还原的铁反应，这使得原位铁渗透反应屏障(PRBS)作为许多受污染场地的首选清理方法迅速被接受。尽管所涉及的确切机制尚未完全阐明，但现场演示表明，在与环境相关的条件下，反应可能会很快。目前，已安装了80多个使用铁作为处理受污染地下水的反应材料的实地规模的可再生燃料电池。然而，关于这些墙中使用的多种类型的铁的相对反应性的问题仍然存在。决定铁PRBS作为修复技术适用性的一个关键变量是有机卤化物降解率。这些速率不仅是正在修复的有机卤化物(即氯代烷与氯代烯)的特性和浓度的函数，而且还与地下水的组成(即pH值、离子含量)、存在的铁量及其结构组成有关。铁的数量或浓度很重要，因为污染物的减少需要污染物和铁表面之间的直接电子转移，或通过表面演化的活性中间体(例如氢气)进行的间接电子转移。观察到的反应速率，如伪一级速率系数(KOBS值)所示，通常与铁浓度成线性关系，这一结果表明表面介导的反应。用于有机卤化物修复的铁金属的类型或组成也显著影响铁的反应性。历史上观察到的不同类型铁的反应性差异主要归因于其表面积的可变性。最近的报告表明，这种额外的变异性是由于铁基材组成的根本差异造成的，但从未得到实验证明。

0348125VikeslandThe career development plan has been broken down into two primary components: a research plan describing experiments to examine the formation and reactivity of nanoscale corrosion products and a teaching plan that is designed to reinvigorate the pedagogical environment of the Introduction to Environmental Engineering class at Virginia Tech.The objective of this project is to evaluate the role that nanoscale corrosion products play in determining the reactivity of the granular iron based treatment schemes used for the remediation of organohalide contaminated subsurface environments. The results from the proposed studies will be used in the development of an improved conceptual model of the phenomena responsible for contaminant remediation within granular iron systems. Using Iron Corrosion to Remediate Contaminated GroundwaterThe discovery that chlorinated solvents readily react with reduced iron has led to rapid acceptance of in situ iron Permeable Reactive Barriers (PRBs) as the cleanup method of choice for many contaminated sites. Although the exact mechanisms involved have not been fully elucidated, field demonstrations indicate that the reactions can be rapid under environmentally relevant conditions. At the current time, over eighty field-scale PRBs employing iron as a reactive material for treatment of contaminated groundwater have been installed. Questions remain, however, concerning the relative reactivities of the numerous types of iron used in these walls. A key variable that dictates the applicability of iron PRBs as a remediation technique is the organohalide degradation rate. These rates are a function not only of the identity and concentration of the organohalide undergoing remediation (i.e., chlorinated alkanes vs. chlorinated alkenes, but also of the groundwater composition (i.e., pH, ionic content), the quantity of iron present, and its structural makeup. The quantity, or concentration, of iron is important because contaminant reduction requires either direct electron-transfer between the contaminant and the iron surface or indirect electron-transfer via surface evolved reactive intermediates (e.g., H2). Observed reaction rates, as evinced by pseudo-first-order rate coefficients (kobs values), typically scale linearly with iron concentration, a result indicative of surface mediated reactions. The type or composition of the iron metal used for organohalide remediation also significantly affects iron reactivity. Observed differences in the reactivity of various types of iron were historically attributed primarily to variability in their surface areas. Recent reports have suggested, but never experimentally documented, that this additional variability results from fundamental differences in the composition of the iron substrates.