ADSORBABILITY OF ALIZARIN RED S ON Fe(III)- AND Pb(II)-TREATED HYDROXYAPATITES IN WATER

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We studied on adsorbability of alizarin red S (ARS) on Fe(III)- and Pb(II)-treated hydroxyapatites in distilled water (H₂O) and phosphate buffer solution (PBS). The Fe(III)-treated apatites indicated high adsorption capacity from their isothermic curves both in H₂O and PBS: The capacities in PBS were larger than those in H₂O. On the other hand, adsorption capacities of Pb(II)-treated apatites in PBS were much lower than those in H₂O. Surface analysis of those treated apatites by electron probe micro analysis and FT-IR microspectroscopy affords significant information on surface element (P, Ca, Fe, or Pb) distribution and interaction patterns between ARS and the corresponding metal (Fe or Pb) sites. Eventually, predominant adsorption mechanisms were elucidated as follows, chelate form adsorption for Fe(III)-treated apatites and salt form adsorption for Pb(II)-treated apatites.