Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States.
Environ Sci Technol. 2012 Feb 7;46(3):1430-8. doi: 10.1021/es203084n. Epub 2012 Jan 20.
The formation of lead dioxide PbO(2), an important corrosion product in drinking water distribution systems with lead-bearing plumbing materials, has been hypothesized to involve Pb(III) intermediates, but their nature and formation mechanisms remain unexplored. This study employed the electrochemical (EC) method of rotating ring disk electrode (RRDE) and quantum chemical (QC) simulations to examine the generation of intermediates produced during the oxidation of Pb(II) to PbO(2). RRDE data demonstrate that PbO(2) deposition and reduction involves at least two intermediates. One of them is a soluble Pb(III) species that undergoes further transformations to yield immobilized PbO(2) nanoparticles. The formation of this intermediate in EC system is mediated by hydroxyl radicals (OH(•)), as was evidenced by the suppression of intermediates formation in the presence of the OH(•) scavenger para-chlorobenzoic acid. QC simulations confirmed that the oxidation of Pb(II) by OH(•) proceeds via Pb(III) species. These results show that Pb(III) intermediates play an important role in the reactions determining transitions between Pb(II) and Pb(IV) species and could impact lead release in drinking water.
二氧化铅（PbO₂）的形成，这是饮用水分配系统中含铅管道材料的重要腐蚀产物，据推测涉及 Pb（III）中间体，但它们的性质和形成机制仍未得到探索。本研究采用电化学（EC）旋转环盘电极（RRDE）方法和量子化学（QC）模拟，研究了 Pb（II）氧化为 PbO₂过程中产生的中间体的生成。RRDE 数据表明，PbO₂的沉积和还原至少涉及两种中间体。其中之一是可溶性 Pb（III）物种，它会进一步转化为固定的 PbO₂纳米颗粒。这种中间体在 EC 体系中的形成是由羟基自由基（OH（•））介导的，这可以通过在存在 OH（•）清除剂对氯苯甲酸的情况下抑制中间体的形成来证明。QC 模拟证实，OH（•）对 Pb（II）的氧化是通过 Pb（III）物种进行的。这些结果表明，Pb（III）中间体在决定 Pb（II）和 Pb（IV）物种之间转化的反应中起着重要作用，并可能影响饮用水中的铅释放。
