Science Inventory

TRANSFORMATION OF PB(II FROM CERRUSITE TO CHLOROPYROMORPHITE IN THE PRESENCE OF HYDROXYAPATITE UNDER VARYING CONDITIONS OF PH

Citation:

Zhang**, P. AND J A. Ryan*. TRANSFORMATION OF PB(II FROM CERRUSITE TO CHLOROPYROMORPHITE IN THE PRESENCE OF HYDROXYAPATITE UNDER VARYING CONDITIONS OF PH. DOI: 10.1021/es98026, ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 33(4):625-630, (1999).

Impact/Purpose:

information

Description:

The soluble Pb concentration and formation of chloropyromorphite [Pb5(PO4)3Cl] were monitored during the reaction of cerrusite (PbCO3), a highly bioavailable soil Pb species, and hydroxyapatite [Ca5(PO4)3OH] at various P/Pb molar ratios under constant and dynamic pH conditions. Under pH-constant systems at pH 4 and below, the dissolution rates of both cerrusite and apatite were rapid, and complete conversion of cerrusite to chloropyromorphite occurred within 60 min when the amount of phosphate added via apatite was stoichoimetrically equal to that needed to transform all added Pb into chloropyromorphite. The concentration of soluble Pb depended upon the solubility of chloropyromorphite. The dissolution rates of apatite and cerrusite decreased with increasing pH, and the transformation was incomplete at pH 5 and above in the 60-min reaction period. The soluble Pb level, therefore, was determined by the solubility of cerrusite. In the pH-dynamic system, which simulated the gastrointestinal tract (GI tract), a complete transformation of Pb from cerrusite to chloropyromorphite was achieved due to the complete dissolution of apatite and cerrusite at the initial low pH. In both the constant and dynamic pH systems XRD analysis indicated that chloropyromorphite was the exclusive reaction product. The differences in transformation rate and the Pb solubility between the constant and dynamic pH systems indicate the significance of kinetics in controlling the bioavailability of Pb and the potential for the reaction to occur during ingestion.

URLs/Downloads:

TRANSFORMATION OF PB(II FROM CERRUSITE TO CHLOROPYROMORPHITE IN THE PRESENCE OF HYDROXYAPATITE UNDER VARYING CONDITIONS OF PH   Exit

Record Details:

Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Product Published Date: 01/06/1999
Record Last Revised: 12/10/2008
OMB Category: Other
Record ID: 107261

Organization:

U.S. ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF RESEARCH AND DEVELOPMENT

NATIONAL RISK MANAGEMENT RESEARCH LABORATORY

LAND REMEDIATION AND POLLUTION CONTROL DIVISION

REMEDIATION AND REDEVELOPMENT BRANCH