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

职业发展计划分为两个主要部分：一项研究计划，描述了研究纳米级腐蚀产物的形成和反应性的实验，以及一项教学计划，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物在确定用于修复有机卤化物污染地下的颗粒铁基处理方案的反应性方面所起的作用环境。拟议研究的结果将用于开发一个改进的概念模型，该模型负责颗粒铁系统内污染物修复的现象。氯化溶剂很容易与还原铁发生反应，这一发现使得原位铁渗透反应屏障（PRBs）迅速被接受为许多污染场地清洁的首选方法。虽然所涉及的确切机制尚未完全阐明，但现场演示表明，在环境相关条件下，反应可以迅速进行。目前，已经安装了80多个采用铁作为反应物质处理受污染地下水的现场规模的核反应堆。然而，关于这些墙中使用的各种铁的相对反应性的问题仍然存在。决定铁PRBs作为一种修复技术适用性的一个关键变量是有机卤化物的降解率。这些速率不仅是进行修复的有机卤化物的特性和浓度（即氯代烷烃与氯代烯烃）的函数，而且还与地下水组成（即pH值、离子含量）、存在的铁的数量及其结构组成有关。铁的数量或浓度很重要，因为污染物还原要么需要污染物和铁表面之间的直接电子转移，要么需要通过表面演化的反应中间体（如H2）间接电子转移。观察到的反应速率，如伪一级速率系数（kobs值）所证明的，通常与铁浓度成线性关系，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。观察到的不同类型铁的反应性差异，历史上主要归因于其表面积的变化。最近的报告表明，这种额外的可变性是由铁底物组成的根本差异造成的，但从未有实验证明。

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.