Collaborative Proposal: Rates and mechanisms of lead phosphate formation, aggregation, and deposition for more efficient corrosion control

1603717 /1604042 Giammar/ HuAging基础设施已被确定为未来几年国家面临的一个问题。其中一个问题是饮用水分配系统中使用的传统铅管。拟议的项目将通过发展对铅-磷酸盐化学的更好和全面的理解，推进有效控制铅腐蚀的科学和工程基础。该研究由以下因素驱动：（a）饮用水中铅的法规不断演变，（B）有关磷酸铅成核、生长、聚集和沉积的速率和机制的科学问题尚未解决。该项目将填补有关磷酸铅矿物的形成和稳定性以及控制磷酸铅沉淀的分子级界面过程的重要知识空白。国家的最先进的技术将能够在原位定量的均匀（在溶液中）和异质（基板上）的磷酸铅的成核和它们的聚集和沉积在管道表面上。观察和预测成核以及区分均质成核和非均质成核的能力是环境化学中的一个前沿领域。对磷酸盐矿物的胶体和界面过程的理解的进展可以为地质学、材料科学、生物医学工程和环境工程领域做出贡献。该项目将表征添加磷酸盐后在现有规模上发展的腐蚀产物的组成，结构和原位变化。这一新知识将与配水系统中的铅腐蚀控制直接相关，也与自然和工程土壤和水生系统中的铅流动性相关。团队？的互补性专业知识将有助于该项目通过将纳米化学和矿物学技术应用于重要的环境工程问题来推进环境研究的基础设施。该项目的目标是：（1）确定控制溶液中磷酸铅的均匀成核和聚集的因素，并量化水化学对这些过程的影响，（2）确定磷酸铅颗粒在管道表面形成的垢上的非均匀成核和沉积速率，以及，（3）能够对磷酸盐应用策略进行基于科学的优化，该策略可以针对特定的水化学和水垢类型进行定制。该方法将建立在解决方案和表面上的过程的基础研究，并考虑在完整的管道中发生的过程。这种综合方法将把基础知识的进步与重要的转化成果联系起来。一个多尺度的方法将使用原子和分子尺度的表征技术，以产生所需的解释胶体和界面过程负责的宏观吸收或释放的铅从管道机械的见解。除了更好地了解铅（Pb）和磷酸盐化学的潜在影响外，拟议的研究还将与涉及课程丰富，学生培训以及K-12学生和专业工程社区的教育活动相结合。

1603717 / 1604042Giammar / HuAging infrastructure has been identified as an issue that faces the Nation in the coming years. One such issue is legacy lead pipes used in drinking water distribution systems. The proposed project will advance the scientific and engineering basis for effective control of lead corrosion by developing a better and thorough understanding of lead-phosphate chemistry. The research is driven by: (a) evolving regulations for lead in drinking water, and, (b) unresolved scientific questions regarding the rates and mechanisms of lead phosphate nucleation, growth, aggregation, and deposition. The project will fill important knowledge gaps regarding the formation and stability of lead phosphate minerals and the molecular-level interfacial processes controlling lead phosphate precipitation. State-of-the-art techniques will enable in situ quantification of the homogeneous (in solution) and heterogeneous (on substrates) nucleation of lead phosphates and their aggregation and deposition on pipe surfaces. The ability to observe and predict nucleation and to distinguish between homogeneous and heterogeneous nucleation is a remaining frontier in environmental chemistry. Advances in the understanding of colloidal and interfacial processes involving phosphate minerals can contribute to the fields of geology, materials science, and biomedical engineering as well as environmental engineering. The project will characterize the composition, structure, and in situ changes of the corrosion products that develop on existing scales after phosphate addition. This new knowledge will have direct relevance to lead corrosion control in water distribution systems, and it is also relevant to lead mobility in natural and engineered soil and aquatic systems. The team?s complementary expertise will help the project advance the infrastructure for environmental research by bringing nano-chemistry and mineralogy techniques to bear on important environmental engineering problems. The project objectives are to: (1) identify factors that control the homogeneous nucleation and aggregation of lead phosphates in solution and quantify the effects of water chemistry on those processes, (2) determine the rates of heterogeneous nucleation and deposition of lead phosphate particles on scales that form on pipe surfaces, and, (3) enable science-based optimization of phosphate application strategies that can be tailored to a particular water chemistry and scale type. The approach will build from fundamental studies of processes in solution and on surfaces, and, the consideration of processes occurring in intact pipes. This integrated approach will link advances in fundamental knowledge with important translational outcomes. A multi-scale approach will use atomic- and molecular-scale characterization techniques to yield mechanistic insights needed to interpret colloidal and interfacial processes responsible for the macroscopic uptake or release of lead from pipes. In addition to the potential impact of a better understanding lead (Pb) and phosphate chemistry, the proposed research will be integrated with educational activities that involve curriculum enrichment, student training, and outreach to K-12 students and the professional engineering community.