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  • 1 Facultad de Ciencias, Universidad Autónoma del Estado de México, 50100 Toluca, Estado de México, Mexico
  • 2 Instituto Nacional de Investigaciones Nucleares, Carr. México-Toluca S/N (km. 36.5), La Marquesa, 52750 Ocoyoacac, Estado de México, Mexico
  • 3 GIP Arronax, 1 rue Aronnax, BP 10112, 48817 Saint Herblain Cedex, France
  • 4 Inserm U892, CHU – Institut de Biologie, 9 quai Moncousu, 44093 Nantes Cedex 1, France
  • 5 CEA, DEN, Saclay, DPC, SECR, LSRM, 91191 Gif sur Yvette, France
  • 6 Université d’Evry, CEA, CNRS, LAMBE, UMR 8587, 91025 Evry, France
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Abstract  

The sorption of Pd(II) on hydroxyapatite (Ca10(PO4)6(OH)2) has been studied at 25 °C as a function of pH, in 0.01 M NaClO4, and 0.01 and 0.025 M Ca(ClO4)2 aqueous background electrolytes and Pd(II) concentration (9.3 to 47 μM), trying to minimize some types of reactions, such as solid dissolution of and metal precipitation. The radiotracer palladium, 109Pd, obtained by neutron irradiation, has been used to calculate the palladium’s distribution coefficients Kd between aqueous and solid phase. A mathematical treatment of results has been made by ion-exchange theory in order to interpret palladium sorption onto treated solid. For this, we take into account the existence of active sites at the hydroxyapatite surface, and the aqueous solution chemistry of palladium as well as the effect of phosphate anions from solid dissolution. The results can be explained as evidence of sorption of the species PdOH+, and of a mixed hydroxo complex of Pd2+ like (XCaO)–PdOH+·nH2O fixed onto {≡Ca–OH} surface sites of the hydroxyapatite.