BINDING MECHANISM OF TRITON X-100 AND TRITON N TO THE SURFACE OF HYDROXYAPATITE IN AN AQUEOUS PHASE

Abstract

Water-insoluble dodecylphosphate (DP) was solubilized by a micelle of a nonionic surfactant such as Triton X-100(TX) and Triton N (TN), forming a mixed micelle. The mixed micelle was adsorbed by HAP after isomorphous substitution of phosphate group of DP for orthophosphate ion on HAP and electrostatic attractive force between a negative charge of DP and Ca²⁺ on HAP. As a result, nonadsorbable nonionic surfactant was adsorbed indirectly to HAP together with DP forming hemi- and/or admicelle. In an aqueous solution of CaCl₂, the solution of nonionic surfactant-DP became turbid. DP was selectively captured by Ca²⁺, resulting in formation of the Ca-DP precipitate, which was separated from the mixed micelle. However, nonionic surfactant remained in an aqueous phase. Thus, the mixed micelle showed different behavior on the surface of HAP and in an aqueous phase.