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FORMATION OF CHLOROPYROMORPHITE FROM GALENA (PBS) IN THE PRESENCE OF HYDROXYAPATITE
Citation:
Zhang**, P. AND J A. Ryan*. FORMATION OF CHLOROPYROMORPHITE FROM GALENA (PBS) IN THE PRESENCE OF HYDROXYAPATITE. DOI: 10.1021/es98031, ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 33(4):618-624, (1999).
Impact/Purpose:
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Description:
Transformation of unstable lead [Pb(II)] forms into insoluble pyromorphite, [Pb5(PO4)3(OH, Cl, F...)], by addition of phosphate to Pb contaminated soil has been proposed as a remediation technology which reduces the mobility and bioavailability of Pb. Under aerobic condition, oxidation of dissolved sulfide increases dissolution of galena (PbS), causing it to become a source of liable Pb forms in soils, sediments and wastes. Thus, a galena ore was reacted with synthetic hydroxyapatite [Ca5(PO4)3OH] under various pH condition to determine the formation rate of pyromorphite and the solubility of galena under the ambient conditions. In a 6 day reaction period the dissolution rate of galena increased with pH due to the oxidation of dissolved sulfide. Correspondingly, formation of chloropyromorphite became apparent in the galena-apatite suspensions with increasing pH. The insignificant effect of mineral P/Pb molar ratio on the formation of chloropyromorphite implied that dissolution of galena was the rate limiting step.
