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Formation of Pyromorphite in Anglesite-Hydroxyapatite Suspensions Under Varying pH Conditions

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Addition of phosphate to lead [Pb(ll)l-cOntarninated soil to immobilize soil Pb by formation of pyromorphite has been proposed as an alternative remediation technique. Lead sulfate (PbS04, anglesite), a Pb-bearing form found in contaminated soils and wastes, was reacted with a synthetic phosphate mineral, hydroxyapa$te [Ca5(PO& OH], under constant pH (PH 2-7) and simulated gastric pH conditions (PH varied from 2 to 7 within 30 rein) to assess the effects of reaction kinetics on the formation rate of chloropyromorphite and the volubility of Pb. Under constant pH condition, complete transformation of anglesite to chloropyromorphite, [Pb5(PO&Cl], was obtained at pH 4 and ... continued below

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Ryan, J.A. & Zhang, P. October 14, 1998.

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This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. It has been viewed 28 times . More information about this article can be viewed below.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Laboratories, Albuquerque, NM, and Livermore, CA
    Place of Publication: Albuquerque, New Mexico

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Description

Addition of phosphate to lead [Pb(ll)l-cOntarninated soil to immobilize soil Pb by formation of pyromorphite has been proposed as an alternative remediation technique. Lead sulfate (PbS04, anglesite), a Pb-bearing form found in contaminated soils and wastes, was reacted with a synthetic phosphate mineral, hydroxyapa$te [Ca5(PO& OH], under constant pH (PH 2-7) and simulated gastric pH conditions (PH varied from 2 to 7 within 30 rein) to assess the effects of reaction kinetics on the formation rate of chloropyromorphite and the volubility of Pb. Under constant pH condition, complete transformation of anglesite to chloropyromorphite, [Pb5(PO&Cl], was obtained at pH 4 and pH 5. At pH 6 and pH 7, the newly formed chloropyromorphite precipitated on the surface of undissolved apatite, The coverage of the apatite surface may reduce apatite dissolution fate and the transformation rate of Pb from anglesite to"chloropyromorphite. Increasing the P/Pb ratio increased the transformation rate, but anglesite was still present after a' 120-min reaction time. in the dynamic pH system, the added apatite was rapidly dissolved at the initial low pH, and complete transformation of anglesite to chloropyromorphite was obtained within 25 min., The soluble Pb level was controlled by the volubility of chloropyromorphite during the entire reaction process. These results demonstrate the effect of reaction kinetics on the formation rate of chloropyromorphite and the mechanisms controlling the solubilization of Pb in the anglesite-apatite system. Furthermore, they illustrate that a complete transformation of ingested anglesite to chloropyromorphite can be achieved. under gastrointestinal tract pH conditions if sufficient phosphate is provided.

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  • Journal Name: Environmental Science and Technology

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  • Other: DE00001372
  • Report No.: SAND98-2302J
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 1372
  • Archival Resource Key: ark:/67531/metadc628194

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • October 14, 1998

Added to The UNT Digital Library

  • June 16, 2015, 7:43 a.m.

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  • Dec. 9, 2016, 4:25 p.m.

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Ryan, J.A. & Zhang, P. Formation of Pyromorphite in Anglesite-Hydroxyapatite Suspensions Under Varying pH Conditions, article, October 14, 1998; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc628194/: accessed January 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.