SGER: Unleaded Drinking Water

这是授予密苏里大学罗拉分校的Jay Switzer教授和Eric W.Bohannan教授的无机化学、生物无机和金属有机化学项目的SGER奖，该奖项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，将确定铅和铜管内侧形成和溶解的氧化膜，如PbO2、PbO、CuO和Cu2O的钝化作用。实际铅服务线内部的氧化物将通过膜生长和溶解的电化学研究进行定量分析和建模。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·肖克博士将从受影响的水区提供管道。采用X射线衍射仪对金属管上完整的氧化膜进行分析，通过Rietveld分析确定氧化膜的物相、晶体取向、晶粒度和应变。用横截面透射电子显微镜(TEM)测定了薄膜的横截面成分和晶粒度。由于铅的软性，将采用聚焦离子束技术来制备薄截面。模型系统还将通过标准的电化学技术，如循环伏安法和电化学石英晶体微天平(EQCM)来研究，以跟踪氧化膜在各种水化学中的生长和溶解。PbO2的正交膜和四方膜都将沉积在EQCM电极上，然后研究在次氯酸盐、氯胺、碳酸盐、正磷酸盐和其他已知存在于城市饮用水中的物种存在下，这些膜的溶解情况。通过在Au或PtEQCM电极上沉积铅层来生长薄膜，以确定次氯酸盐和氯胺是否能将表面氧化成PbO2。这些薄膜将通过掠射角X射线衍射，可能还有XPS进行分析，以验证薄膜的形成。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，因为铜与铅接触可能会导致电偶反应，从而铜被氧化(和溶解)，PbO2钝化层被还原。这种电偶反应可能发生在铅管和铜管的连接处，铜管上的铅焊点，以及“无铅”黄铜灯具中。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。密苏里大学罗拉分校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团队将为研究生和博士后助理提供跨学科培训。

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.