Formation of Pb(III) Intermediates in the Electrochemically Controlled Pb(II)/PbO₂ System

Abstract

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.

Standard Redox Potentials of Fe(III) Aqua Complexes Included into the Cavities of Cucurbit[n]urils (n = 6–8): A DFT Forecast

“…Quantum chemical methods previously have been successfully used in many studies for calculating standard redox potentials involving a number of complexes in aqueous solutions as well as in proteins. In most cases, good agreement was achieved between the calculated and available experimental values of the electrode potentials. − Unfortunately, examples of the application of quantum chemistry methods for predicting the redox potentials of complexes embedded in CB­[ n ] are not known to us. For this reason, in this work, we first attempted to calculate the standard redox potential of Fe­(III)@CB­[ n ]/Fe­(II)@CB­[ n ] ( n = 6–8) in comparison with the experimental value for the half-reaction Fe­(III)/Fe­(II) in the bulk of aqueous solution.…”

Differential Cytotoxicity of Haloaromatic Disinfection Byproducts and Lead Co-exposures against Human Intestinal and Neuronal Cells

“…In recent surveys by American Water Works Association, approximately 30% of community water systems reported service lines containing lead, and the total number of lead service lines in the United States was estimated to be 6.1 million . Besides lead pipes, lead-containing brass and lead–tin solder are still widely present in many premise plumbing systems and essentially exist as nonpoint sources of lead. , When exposed to residual chlorine disinfectant in drinking water, lead plumbing materials are oxidized to solid lead dioxide (PbO 2 ). − The PbO 2 (s) can react with reducing components in water to generate soluble Pb­(II). − Per the Lead and Copper Rule by the U.S. EPA, the concentration of dissolved lead should not exceed an action level of 15 μg/L. The guideline value for lead in drinking water set by World Health Organization is 10 μg/L…”

Copper Drinking Water Pipes as a Previously Undocumented Source of Silver-Based Nanoparticles

“…The main sources of copper in an urban environment are tap water and roof runoff. 35−37 For nanoparticles that migrate from the pipe material to tap water, previous studies have only discussed lead dioxide (PbO 2 )-NPs, 38 Cu-NPs, 39 and Fe-NPs 40 to date. Given the fact that massive volumes of tap water significantly influence wastewater streams and, as we show in this study, that tap water can contain non-negligible amounts of Ag-b-NPs, tap water as a source of Ag-b-NPs in aquatic environments can no longer be ignored in risk assessment studies and flow analysis models.…”

“…Until recently, water supply pipework was thought to be the main source of ionic heavy metal species in tap water, such as cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), selenium (Se), and zinc (Zn) due to the corrosion of the plumbing material. − Copper, a very common water pipe material, always contains traces of silver, a natural impurity, which is capable of releasing silver ions as well as Ag-b-NPs in the ng L –1 range into tap water that passes through copper pipes. The main sources of copper in an urban environment are tap water and roof runoff. − For nanoparticles that migrate from the pipe material to tap water, previous studies have only discussed lead dioxide (PbO 2 )-NPs, Cu-NPs, and Fe-NPs to date. Given the fact that massive volumes of tap water significantly influence wastewater streams and, as we show in this study, that tap water can contain non-negligible amounts of Ag-b-NPs, tap water as a source of Ag-b-NPs in aquatic environments can no longer be ignored in risk assessment studies and flow analysis models.…”