Performance and Mechanisms of Iron Electrocoagulation for Removal of Chromium(VI) from Drinking Water

CBET-1335613位于圣路易斯华盛顿大学的Daniel Giammar六铬(VI)是一种有毒污染物，已在私人和公共供水以及经处理的饮用水中观察到。目前的饮用水标准只适用于总铬，它可以以铬(VI)的形式存在，也可以是毒性小得多的铬(III)，甚至在低浓度时也是一种营养。新的专门针对铬(VI)的饮用水标准很可能会被实施，而铁的电凝聚是一种有可能达到可能要求的低浓度的技术。在铁电凝聚中，在两个铁电极之间施加直流电。其中一个电极被氧化，将铁(II)释放到溶液中，这种可溶的铁(II)可以直接还原铬(VI)或被氧化成铁(III)，生成氧化铁固体，铬(VI)可以被还原并吸附在其上。铁电凝聚去除铬(VI)有多种途径，包括均相和非均相化学还原、吸附和共沉淀。本研究项目的主要目的是促进对铁电凝聚去除铬(VI)的机理的了解。该项目将在实验室规模的电凝聚反应器中评估在广泛的水化学条件下的电凝聚性能。分析方法将跟踪总溶解铬和铬(VI)的变化，以达到法规正在考虑的非常低的水平。这项研究将使用先进的光谱和稳定同位素工具来确定电凝聚反应器中发生的主要反应机理。X射线吸收光谱将在国家用户设施中进行，将提供对与反应堆中产生的固体相关的铬的氧化状态和分子尺度配位的深入了解。铬的稳定同位素分馏可以用来诊断特定的反应机理。电凝聚性能的数学模型将整合来自实验室规模实验的机械洞察力和数据，从而能够在广泛的条件下预测性能。这项研究将使处理策略的优化设计和铬(VI)去除处理性能的准确预测成为可能。该项目将提供科学信息，帮助改善饮用水中六价铬的去除，六价铬是一种关键的国家利益污染物。这项研究将确定水化学对该过程中涉及的反应的影响，这将使为广泛的饮用水水源设计有效的铬(VI)去除策略成为可能。研究活动将确定环境工程以及地球科学和材料科学感兴趣的反应机制。该项目对光谱表征和稳定同位素工具的全面应用将推进环境工程研究的整体基础设施。该项目的教育和推广部分将加强研究生和本科生的教学，并促进早期学生对科学和工程的兴趣。

CBET-1335613Daniel GiammarWashington University in St. LouisChromium(VI) is a toxic contaminant that has been observed in private and public water supplies as well as in treated drinking water. Current drinking water standards are only applicable to total chromium, which can be present as chromium(VI) as well as the much less toxic form of chromium(III) that is even a nutrient at low concentrations. It is likely that new drinking water standards specific to chromium(VI) will be implemented, and iron electrocoagulation is a technology with the potential to achieve the low concentrations that may be required. In iron electrocoagulation a direct current is applied between two iron electrodes. One of the electrodes is oxidized to release iron(II) to solution, and this soluble iron(II) can directly reduce chromium(VI) or be oxidized to iron(III) to produce iron oxide solids on which chromium(VI) can be reduced and adsorbed. Iron electrocoagulation for chromium(VI) removal has multiple removal pathways that involve homogeneous and heterogeneous chemical reduction, adsorption, and co-precipitation. The primary objective of this research project is to advance the mechanistic understanding of chromium(VI) removal by iron electrocoagulation. The project will evaluate electrocoagulation performance over a broad range of water chemistry conditions in a laboratory-scale electrocoagulation reactor. Analytical methods will track changes in both total dissolved chromium and chromium(VI) to the very low levels that are being considered for regulations. The investigation will use advanced spectroscopic and stable isotope tools to identify the dominant reaction mechanisms occurring in the electrocoagulation reactor. X-ray absorption spectroscopy, which will be performed at national user facilities, will provide insights into the oxidation state and molecular-scale coordination of chromium associated with the solids generated in the reactor. Stable isotope fractionation of chromium can be diagnostic of specific reaction mechanisms. A mathematical model for electrocoagulation performance will integrate the mechanistic insights and data from the laboratory-scale experiments to enable predictions of performance over a broad range of conditions. The research will enable the optimal design of treatment strategies and accurate prediction of treatment performance for chromium(VI) removal.This project will provide scientific information that will help improve the removal of hexavalent chromium, a contaminant of critical national interest, from drinking water. The research will determine the influence of water chemistry on the reactions involved in the process, which will enable the design of effective strategies for chromium(VI) removal for a broad range of drinking water sources. The research activities will determine reaction mechanisms of interest in environmental engineering as well as earth science and materials science. The project's overall application of spectroscopic characterization and stable isotope tools will advance the overall infrastructure for environmental engineering research. The educational and outreach components of the project will enhance graduate and undergraduate teaching and promote early student interest in science and engineering.