SGER: Unleaded Drinking Water

这是SGER奖在无机，生物无机和有机化学计划教授杰伊瑞士和埃里克W。位于罗拉的密苏里州大学的博汉南从材料科学和电化学的角度支持对当前紧迫的公共卫生问题的研究，该问题涉及饮用水供应中的铅。 在常用的水消毒剂次氯酸盐和氯胺的存在下，将确定铅和铜管道内部氧化物膜（例如PbO2、PbO、CuO和Cu2O）的形成和溶解的钝化作用。将对实际铅服务线内部的氧化物进行定量分析，并利用膜生长和溶解的电化学研究进行建模。位于俄亥俄州辛辛那提的美国环境保护局供水和水资源司的迈克尔·肖克博士将提供来自受影响水区的管道。 将通过X射线衍射（XRD）分析金属管道上完整的氧化膜，以便通过Rietveld分析确定相、晶体取向、晶粒尺寸和应变。 横截面透射电子显微镜（TEM）将用于确定膜的横截面组成和晶粒尺寸。 由于铅的柔软性，将采用聚焦离子束技术来制备薄的横截面。 模型系统也将通过标准电化学技术进行研究，如循环伏安法和电化学石英晶体微天平（EQCM），以跟踪各种水化学中氧化膜的生长和溶解。 将正交和四斜晶系的PbO2薄膜沉积到EQCM电极上，然后研究在次氯酸盐、氯胺、碳酸盐、正磷酸盐和已知存在于城市饮用水中的其他物质的存在下薄膜的溶解。 通过在Au或Pt EQCM电极上沉积Pb层的膜生长将被跟踪以确定次氯酸盐和氯胺是否可以将表面氧化成PbO2。 将通过掠射角XRD和可能的XPS分析这些膜，以验证膜的形成。 虽然重点是确定饮用水中铅含量升高的原因，但也将研究铜管溶解的问题。这些问题可能是相关的，因为与Pb接触的Cu可能导致原电池反应，由此Cu被氧化（和溶解）并且PbO2钝化层被还原。 这种电偶反应可能出现在铅和铜管道的交界处，在铜管道上的铅焊接点，并在“无铅”黄铜夹具。这项工作可以从化学和材料科学的角度为市政供水系统提供指导，以帮助降低饮用水中的铅含量。 位于罗拉的密苏里州大学材料研究中心的化学家、化学工程师和材料科学家组成的研究小组将为研究生和博士后提供跨学科的培训。

This is SGER award in the Inorganic, Bioinorganic and Organometallic Chemistry Program to Professors Jay Switzer and Eric W. Bohannan at the University of Missouri at Rolla supports research on a current, urgent, public health problem involving lead in drinking water supplies from the perspective of materials science and electrochemistry. The passivation role of the formation and dissolution of oxide films, such as PbO2, PbO, CuO and Cu2O, on the inside of lead and copper pipes will be determined in the presence of commonly-used water disinfectants, hypochlorite and chloramines. The oxides on the inside of actual Pb service lines will be quantitatively analyzed and modeled with electrochemical studies of film growth and dissolution. Dr. Michael Schock of the Water Supply and Water Resources Division of the U.S. Environmental Protection Agency in Cincinnati, Ohio will provide pipes from affected water districts. The oxide films intact on the metal pipes will be analyzed by X-ray diffraction (XRD) in order to determine phases, crystallographic orientation, grain size and strain by Rietveld analysis. Cross-sectional transmission electron microscopy (TEM) will be used to determine the cross-sectional composition and grain size of the films. Due to the softness of Pb, focused ion beam techniques will be employed to prepare the thin cross-sections. Model systems will also be studied by standard electrochemical techniques, such as cyclic voltammetry, and the electrochemical quartz crystal microbalance (EQCM) to follow the growth and dissolution of oxide films in various water chemistries. Both orthorhombic and tetragonal films of PbO2 will be deposited onto EQCM electrodes followed by studies of the dissolution of the films in the presence of hypochlorite, chloramines, carbonate, orthophosphate, and other species known to be present in municipal drinking water. Film growth by depositing Pb layers on Au or Pt EQCM electrodes will be followed to determine whether hypochlorite and chloramines can oxidize the surface to PbO2. These films will be analyzed by glancing angle XRD, and possibly XPS, to verify the film formation. Although the emphasis is on determining the cause of elevated lead levels in drinking water, the problem of Cu pipe dissolution will also be studied. These problems may be correlated, because Cu in contact with Pb may lead to a galvanic reaction whereby the Cu is oxidized (and dissolved) and the PbO2 passivating layers are reduced. This galvanic reaction might arise at the junctions of Pb and Cu pipes, at Pb solder joints on Cu pipes, and in "lead-free" brass fixtures. This work may provide guidance from a chemical and materials science perspective to municipal water systems to assist in lowering lead levels in drinking water. The research team of chemists, chemical engineers, and materials scientists at the Materials Research Center at the University of Missouri at Rolla will provide interdisciplinary training for graduate students and postdoctoral associates.