EAGER: Development of a Novel in situ Electrochemical Tool to Understand Redox Pathways of Hexavalent Chromium and Its Intermediate Formation

金属铬在社会上有许多应用。然而，如果处置不当，它也会进入地下和地表沃茨。虽然这种情况通常发生在微量，但在较高浓度下可能会对健康产生不利影响。 它在两种氧化态之间循环，六价形式有毒。该项目涉及一种理论上合理，但风险高，未经测试的方法，具有重大的潜在影响，以开发一种检测水中铬的新方法。该项目将创建一个新的旋转环-盘电极为基础的工具，有可能改变环境工程界的化学过程，涉及水质，公共卫生和监管过程的理解。EAGER项目将开发一种新的原位电化学工具，用于检测三价铬Cr（III）物质在饮用水中氧化过程中的铬中间体。由于消毒剂对残留Cr（III）的氧化，在饮用水中可能会无意中形成高毒性六价铬Cr（VI），通常以含氧阴离子CrO 4 2-的形式存在。然而，Cr（III）氧化的机制在很大程度上仍未被探索。主要研究者（PI）实验室的初步研究表明，Cr（VI）的产率受元素反应控制，该反应涉及形成Cr中间物质，然后是这些中间物质的相关分解。本项目旨在开发一种具有多级旋转环盘电极的新型电化学系统，以定量研究短寿命四价和五价铬物种的形成，即，Cr（IV）和Cr（V）。目前，通过Cr（III）氧化形成Cr（VI）的详细机制知之甚少。尽管人们普遍认为，Cr（III）的低溶解度阻止了其在饮用水中的释放，并且Cr（III）在水处理过程的下游是化学惰性的，但这些假设是不充分的。由于监管机构正在考虑制定更严格的饮用水标准，因此迫切需要了解Cr（VI）形成的基本机制，以制定更好的控制策略。本研究将评估这些中间物种的作用有关的Cr（VI）发生在饮用水中。具体而言，在该项目中，将开发两种新颖且先进的电极系统来检查Cr中间物质的性质：（1）最先进的贵金属电极（即，金和铂）用于均相Cr（III）氧化研究;以及（2）内部构建的电极，具有沉积的Cr（III）矿物，用于非均相Cr（III）氧化研究。本研究的结果将建立一个协议，旋转环盘电极为基础的电化学分析的铬中间体和探索的基本机制与铬（VI）的形成。 本研究的结果将建立一个协议，旋转环盘电极为基础的电化学分析铬中间体和探索与铬（VI）形成在水生系统中的基本机制。该项目涉及一种与传统间歇反应器系统截然不同的电化学方法来研究金属氧化还原化学，并应用表面电化学和分析化学的新专业知识，在新的研究领域中进行新的发现。

1619915LiuThe metal chromium has many applications in society. However, when disposed of improperly, it can also find its way into ground and surface waters. While this usually happens in trace quantities, at higher concentrations it may cause adverse health effects. It cycles between two oxidation states and is toxic in the hexavalent form. This project involves a theoretically sound, but high-risk, untested approach with significant potential impact, to develop a new method of detection of chromium in water. This project will create a new rotating ring-disk electrodes-based tool with the potential to transform the environmental engineering community's understanding of chemical processes that relate to water quality, public health, and regulatory processes.This EAGER project will develop a novel in situ electrochemical tool for the detection of chromium intermediate species during the oxidation of trivalent chromium Cr(III) species in drinking water. Formation of highly toxic hexavalent chromium Cr(VI, typically in the form of oxyanion CrO4 2-, can inadvertently take place in drinking water due to the oxidation of residual Cr(III) by disinfectants. However, the mechanisms of Cr(III) oxidation remain largely unexplored. Preliminary investigations in the principal investigator's (PI's) laboratory indicates that the yield of Cr(VI) is controlled by elemental reactions involving the formation of Cr intermediate species, followed by the associated decomposition of these intermediate species. This project aims to develop a novel electrochemical system with multi-stage rotating ring-disk electrodes to quantitatively investigate the formation of short-lived tetravalent and pentavalent chromium species, i.e., Cr(IV) and Cr(V). Currently, the detailed mechanisms of Cr(VI) formation via Cr(III) oxidation are poorly understood. Although it is widely presumed that the low solubility of Cr(III) prevents its release in drinking water and that Cr(III) is chemically inert downstream of water treatment processes, these presumptions are inadequate. Since Cr(VI) is under consideration by regulatory agencies for more stringent drinking water standards, it is urgent to understand the fundamental mechanisms of Cr(VI) formation to develop better control strategies. This research will assess the role of these intermediate species relevant to Cr(VI) occurrence in drinking water. Specifically, in this project, two novel and advanced electrode systems will be developed to examine the nature of Cr intermediate species: (1) state-of-the-art noble metal electrodes (i.e., gold and platinum) for homogeneous Cr(III) oxidation investigation; and, (2) in-house built electrode with deposited Cr(III) minerals for heterogeneous Cr(III) oxidation investigation. Outcomes of this research will establish a protocol for rotating ring-disk electrodes-based electrochemical analysis of chromium intermediates and exploration of fundamental mechanisms associated with Cr(VI) formation. Outcomes of this research will establish a protocol for rotating ring-disk electrodes-based electrochemical analysis of chromium intermediates and exploration of fundamental mechanisms associated with Cr(VI) formation in aquatic systems. The project involves a radically different electrochemical approach in contrast to a traditional batch reactor system to study metal redox chemistry, and applies new expertise of surface electrochemistry and analytical chemistry to engage novel discoveries in a new area of research.