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

0348125 Vikesland职业发展计划分为两个主要部分：一个研究计划，描述了实验，以检查纳米腐蚀产物的形成和反应性和教学计划，旨在振兴教学环境的介绍环境工程类在弗吉尼亚理工大学。这个项目的目标是评估的作用，纳米腐蚀产物中发挥确定用于有机卤化物污染的地下环境的补救的粒状铁基处理方案的反应性。从拟议的研究结果将被用来在一个改进的概念模型的现象负责颗粒铁系统内的污染物修复的发展。利用铁腐蚀修复受污染的地下水氯化溶剂容易与还原铁发生反应的发现，使人们迅速接受原位铁渗透反应屏障（PRB）作为许多污染场地的首选清除方法。 虽然所涉及的确切机制尚未完全阐明，但现场演示表明，在与环境相关的条件下，反应可能很快。 目前，已经安装了80多个现场规模的PRB，其采用铁作为用于处理受污染的地下水的反应材料。 然而，关于这些墙壁中使用的多种铁的相对反应性，仍然存在问题。 决定铁PRB作为修复技术的适用性的一个关键变量是有机卤化物降解率。 这些速率不仅是经历修复的有机卤化物的特性和浓度的函数（即，氯代烷烃与氯代烯烃，而且地下水成分（即，pH、离子含量）、存在的铁的量及其结构组成。铁的量或浓度是重要的，因为污染物还原需要污染物和铁表面之间的直接电子转移或经由表面析出的反应性中间体（例如，H2）。 观察到的反应速率，如由伪一阶速率系数（kobs值）所表明的，通常与铁浓度成线性比例，这是表面介导反应的结果。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反应性。观察到的各种类型的铁的反应性的差异历史上主要归因于其表面积的变化。最近的报告表明，但从来没有实验记录，这种额外的可变性的结果从根本上的差异，在组成的铁基板。

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.