Transformation of Pb (II) from cerrusite to chloropyromorphite in the presence of hydroxyapatite under varying conditions of pH.
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 stoichiometrically 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 XRO analysis indicated that chloropyromorphite was the exclusive reaction product. (...)
Mots-clés Pascal : Pollution sol, Plomb II Carbonate, Décontamination, Immobilisation, Apatite hydroxylée, Calcium phosphate, Réaction chimique, Dissolution, Biodisponibilité, Effet milieu, pH, Cerrusite, Chloropyromorphite
Mots-clés Pascal anglais : Soil pollution, Lead II Carbonates, Decontamination, Immobilization, Hydroxyapatite, Calcium phosphate, Chemical reaction, Dissolution, Bioavailability, Medium effect, pH
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 99-0146986
Code Inist : 001D16D05. Création : 16/11/1999.