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The Inhibition Of Pb(IV) Oxide Formation In Chlorinated Water By Orthophosphate
LYTLE, D. A., M. R. SCHOCK, AND K. SCHECKEL. The Inhibition Of Pb(IV) Oxide Formation In Chlorinated Water By Orthophosphate. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 43(17):6624-6631, (2009).
Historically, understanding lead solubility and its control in drinking water has been based on Pb(II) chemistry. Unfortunately, there is very little information available regarding the nature of Pb(IV) oxides in finished drinking water and water distribution systems, and the conditions under which they persist. The objective of this research was to explore the impact of orthophosphate on the realistic pathways that lead to teh formation of Pb(IV) oxides in chlorinated water. The results of XRD and XANES analysis showed that, in the absence of orthophosphate (DIC = 10 mg C/L, 24oC, pH 7.75-8.1, 3 mg Cl2/L goal), Pb(IV) oxides formed with time following a transformation from the Pb(II) mineral hydrocerussite. Under the same experimental conditions, orthophosphate dosing inhibited the formation of Pb(IV) oxides, The Pb(II) mineral hydroxypyromorphite, Pb5(PO4)3OH, was the only mineral phase identified during the entire study of over 600 days, although the presence of some chloropyromorphite, Pb5(PO4)3Cl, could not be ruled out. The conclusions were further supported by SEM, TEM, and XANES analysis of lead colloids, and the lead precipitation experiments conducted in the absence free chlorine. The findings provide an important explanation for the absence of Pb(IV) oxides in some water systems that have used, or currently use, orthophosphate for corrosion control when otherwise, based on disinfection practices and water quality, its presence would be anticipated, as well as why the conversion from free chlorine to chloramines was not observed to increase lead release.
To explore the impact of orthophosphate on the realistic pathways that lead to the formation of Pb(IV) oxides in chlorinated water.
URLs/Downloads:THE INHIBITION OF PB(IV) OXIDE FORMATION IN CHLORINATED WATER BY ORTHOPHOSPHATE Exit
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
LAND REMEDIATION AND POLLUTION CONTROL DIVISION
WASTE MANAGEMENT BRANCH