Role of Pb(II) defects in the mechanism of dissolution of plattnerite (β-PbO2) in water under depleting chlorine conditions.

Destabilization of lead corrosion scales present in plumbing materials used in water distribution systems results in elevated lead concentrations in drinking water. Soluble lead release caused by changes in water chemistry has been linked to dissolution of lead carbonate and/or lead oxide solid phases. Although prior studies have examined the effects of varying water chemistry on the dissolution of plattnerite (β-PbO2), β-PbO2 dissolution under depleting chlorine conditions is poorly understood. This paper reports results obtained for long-term batch dissolution experiments for solid phase β-PbO2 under depleting chlorine conditions. Results indicate that the initial availability of free chlorine effectively depresses dissolved lead concentrations released from β-PbO2. However, the dissolved lead levels remained low (∼4 μg/L) even after free chlorine was depleted. Detailed spectroscopic characterization of solid samples collected during the β-PbO2 experiments indicates that changes in the electronic structure of PbO2 occurred during the dissolution. This further points out that Pb2+ defects present in crystalline β-PbO2 play a dominant role in the dissolution of this solid phase.