Formal Casey L, Lytle Darren A, Harmon Stephen, Wahman David G, DeSantis Michael K, Tang Min
ORAU Contractor at U.S. Environmental Protect Agency, Office of Research and Development (ORD), Center for Environmental Solutions & Emergency Response (CESER), Water Infrastructure Division (WID), 26 W. Martin Luther King Dr., Cincinnati, Ohio 45268, USA.
U.S. Environmental Protect Agency, ORD, CESER, WID, 26 W. Martin Luther King Dr., Cincinnati, Ohio 45268, USA.
Environ Sci (Camb). 2024 Apr 30;10(7):1623-1636. doi: 10.1039/d4ew00152d.
Orthophosphate (PO) is a commonly used corrosion control treatment to reduce lead (Pb) concentrations in drinking water. PO reduces Pb concentrations by forming relatively insoluble lead phosphate (Pb-PO) minerals. In some cases, however, Pb-PO minerals have been observed to form nanoparticles, and if suspended in water, these nanoparticles can be mobile and reach consumer taps. Although recent research on Pb-PO particles has been performed, there remains a need to improve our understanding of the nature of Pb-PO nanoparticles. For that reason, Pb precipitation experiments were conducted to generate Pb-PO nanoparticles in bench scale studies for analysis. The study objective was to observe how pH, dissolved inorganic carbon (DIC), and PO impacted the properties of Pb-PO particles. Specifically, particle size, surface charge, mineralogy, and solubility were analysed. Hydrocerussite was precipitated when no PO was present, hydroxypyromorphite (Pb(PO)OH) nanoparticles (<100 nm diameter) were precipitated when excess PO relative to Pb necessary to completely precipitate the mineral was present, and a mixture of the two minerals was precipitated when an insufficient amount of PO was present. Hydroxypyromorphite particles were less soluble than hydrocerussite by up to two orders of magnitude. The estimated of 10 in this work closely aligned with previous estimates that ranged from 10 to 10. Hydroxypyromorphite particles would not settle in water which was likely due to their small size and high negative charge. The mobility and size of these particles indicates that there are potential implications for such particulate Pb to remain suspended in water and thus be present in the tap water.
正磷酸盐（PO）是一种常用的腐蚀控制处理方法，用于降低饮用水中的铅（Pb）浓度。PO通过形成相对不溶性的磷酸铅（Pb-PO）矿物质来降低Pb浓度。然而，在某些情况下，已观察到Pb-PO矿物质会形成纳米颗粒，如果悬浮在水中，这些纳米颗粒可能会移动并到达消费者的水龙头。尽管最近已经对Pb-PO颗粒进行了研究，但仍有必要加深我们对Pb-PO纳米颗粒性质的理解。因此，进行了Pb沉淀实验，以便在实验室规模的研究中生成Pb-PO纳米颗粒进行分析。研究目的是观察pH值、溶解无机碳（DIC）和PO如何影响Pb-PO颗粒的性质。具体而言，分析了颗粒大小、表面电荷、矿物学和溶解度。当不存在PO时，会沉淀出碳酸铅矿；当存在相对于完全沉淀该矿物质所需的Pb过量的PO时，会沉淀出直径小于100nm的羟磷灰石（Pb(PO)OH）纳米颗粒；当PO量不足时，会沉淀出这两种矿物质的混合物。羟磷灰石颗粒的溶解度比碳酸铅矿低多达两个数量级。这项工作中估计的10与先前范围为10至10的估计值密切一致。羟磷灰石颗粒不会在水中沉降，这可能是由于它们的尺寸小和负电荷高。这些颗粒的迁移率和尺寸表明，这种颗粒状Pb有可能悬浮在水中并因此存在于自来水中。
