Effect of Added Salt on the Adsorption of Dodecyl Sulfate Ion and Concurrent Release of Phosphate and Calcium Ions at the Surface of Hydroxyapatite(Physical,Chemical)

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Concentrations of phosphate ion([Pi]_f) and calcium ion [Ca^<2+>_f) liberated from the surface of hydroxyapatite(Ca_10(PO_4)_6(OH)_2; HAP) during the adsorption of dodecyl sulfate ion(DS^-) onto HAP were determined at variovis concentrations of added salt(NaCl or Na_2HPO_4). The effects of added salt on the relationships among [Pi]_f, [Ca^<2+>]_f, the concentration of DS^-([DS^-]_f), and the adsorbed amount of DS^-(X_<DS^->) are discussed. The amount of X_<DS^-> increased monotonously with the concentration of NaCi added([NaCl]_f). However, the equilibrium concentrations of phosphate ion(Pi) and calcium ion(Ca^<2+>) changed in a complex manner with [NuCl]_f. It was concluded that ions on the surface of HAP were partly ion-exchanged with those of sodium dodecyl sulfate and NaCl, and that Ca^<2+> and Na^+ were bound competitively as counter-ions to DS^- micelles. On the other hand, when Na_2HPO_4. was added to the solution, added Pi(i.e., one of the lattice ions for HAP) had a drastic effect on X_<DS^-> and [Ca^<2+>]_f. The adsorbed amount of DS^- decreased with increasing concentration of added Na_2HPO_4 owing to competitive adsorption between DS^- and added Pi. The equilibrium concentration of Ca^<2+>, [Ca^<2+>]_f, decreased for two reasons. First, adsorbed Pi inhibits the release of Ca^<2+> from the surface of HAP by virtue of the electrostatic attractive force. Secondly, the excess Pi remaining in the solution prevents Ca^<2+>-release from the surface of HAP since the solubility product for HAP must remain constant.
社団法人日本薬学会の論文
1987-06-25

Effect of Added Salt on the Adsorption of Dodecyl Sulfate Ion and Concurrent Release of Phosphate and Calcium Ions at the Surface of Hydroxyapatite(Physical,Chemical)

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