title: Modification of Hydroxyapatite with Ion-Selective Complexants: 1-Hydroxyethane-1,1-diphosphonic Acid.
abstract: Hydroxyapatite (HAP) was modified with 1-hydroxyethane-1,1-diphosphonic acid (HEDP), and its effect on divalent metal ion binding was determined. HAP was synthesized from calcium hydroxide and phosphoric acid. After calcination, it was modified with HEDP, and the influence of time and temperature on the modification was investigated. HEDP incorporation increased as its initial solution concentration increased from 0.01 to 0.50 M. Unmodified and modified HAP were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and specific surface area analysis. Ca/P ratios, acid capacities, and phosphorus elemental analyses gave the effect of modification on composition and surface characteristics. A high reaction temperature produced new phosphonate bands at 993, 1082, and 1144 cm-1that indicated the presence of HEDP. HAP modification at a high temperature-long reaction time had the highest HEDP loading and gave the sharpest XRD peaks. The emergence of new HAP-HEDP strands was observed in SEM images for treated samples while EDS showed high phosphorus contents in these strands. Modified HAP had a high acid capacity from the additional P-OH groups in HEDP. The P(O)OH groups maintain their ability to bind metal ions within the HAP matrix: contacting the modified HAP with 10-4N nitrate solutions of five transition metal ions gives an affinity sequence of Pb(II) > Cd(II) > Zn(II) > Ni(II) > Cu(II). This result is comparable to that of commercially available di(2-ethylhexyl)phosphoric acid, a common solvent extractant, and the trend is consistent with the Misono softness parameter of metal ion polarizabilities.
authors: Department of Chemistry, Graduate Center of the City University of New York , 365 Fifth Avenue, New York, New York 10016, United States ; Department of Chemistry, Hunter College of the City University of New York , 695 Park Avenue, New York, New York 10065, United States.
authors: Yasmine
authors: Y
authors: Daniels
authors: Université de Toulouse , Ecole des Mines d'Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09, France.
authors: Nathalie
authors: N
authors: Lyczko
authors: Université de Toulouse , Ecole des Mines d'Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09, France.
authors: Ange
authors: A
authors: Nzihou
authors: Department of Chemistry, Graduate Center of the City University of New York , 365 Fifth Avenue, New York, New York 10016, United States ; Department of Chemistry, Hunter College of the City University of New York , 695 Park Avenue, New York, New York 10065, United States.
authors: Spiro D
authors: SD
authors: Alexandratos