Decrease in the Solubility Product of Hydroxyapatite by the Adsorption of Surface-Active Ion

Abstract

The solubility product (K_sp) of hydroxyapatite (HAP) in ionic surfactant solutions decreased with an increase in the adsorbed amount of the surface-active ions (dodecylammonium and dodecyl sulfate ions). In the presence of nonionic surfactant (polyoxethylene(10) octylphenyl ether), K_sp was almost constant within the limit of experimental error. It was concluded that the decrease in K_sp is due to the decrease in the chemical potential of HAP through the adsorption of the surface-active ion on HAP, and due to the spontaneous change in the constituent ions of the HAP surface (i.e., surface complex formation) by ion-exchange with the surface-active ion.