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

基础设施老化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遗留铅管。该项目将通过对磷酸铅化学的深入了解，为有效控制铅腐蚀提供科学和工程基础。这项研究是由以下因素推动的：(a)饮用水中铅的不断发展的法规，以及(b)关于磷酸铅成核、生长、聚集和沉积的速率和机制的未解决的科学问题。该项目将填补关于磷酸铅矿物的形成和稳定性以及控制磷酸铅沉淀的分子水平界面过程的重要知识空白。最先进的技术将能够对磷酸铅的均相（溶液中）和非均相（基底上）成核及其在管道表面的聚集和沉积进行现场量化。观察和预测成核以及区分均相和非均相成核的能力是环境化学的前沿。对涉及磷酸盐矿物的胶体和界面过程的理解的进步可以为地质学、材料科学、生物医学工程以及环境工程领域做出贡献。该项目将描述磷酸盐添加后在现有鳞片上形成的腐蚀产物的组成、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。团队吗?美国的互补专业知识将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，帮助该项目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)确定在管道表面形成的水垢上磷酸铅颗粒非均匀成核和沉积的速率；(3)实现基于科学的磷酸盐应用策略优化，可以针对特定的水化学和水垢类型进行定制。该方法将建立在溶液和表面过程的基础研究之上，并考虑完整管道中发生的过程。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。多尺度的方法将使用原子和分子尺度的表征技术来产生解释胶体和界面过程所需的机制见解，这些过程负责从管道中摄取或释放铅。除了更好地了解铅（Pb）和磷酸盐化学的潜在影响外，拟议的研究将与教育活动相结合，包括课程丰富，学生培训，以及向K-12学生和专业工程社区的推广。

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.