Surface properties of HAP particles obtained by hydrothermal decomposition of urea and calcium-EDTA chelates

摘要

In this paper surface properties of calcium-hydroxyapatite, synthesized by modified hydrothermal reaction of urea and Ca(EDTA){sup}(2-) in phosphate solutions, as well as the dependence of calcium hydroxyapatite dispersion stability on pH were determined. The specific surface area of calcium-hydroxyapatite was experimentally found to be 67 m{sup}2/g. The point of zero charge (PZC) of indifferent KCl electrolyte of 6.8 ± 0.1 was determined by the batch equilibration method. From the dependence of surface charge density on pH and electrolyte concentration, the intrinsic equilibrium constant of surface groups pK{sub}(a{sub}2){sup}(int) was determined to be 8.3 ± 0.1, while pK{sub}(a{sub}1){sup}(int), calculated from the pK{sub}(a{sub}2){sup}(int) and point of zero charge values, is 5.3±0.1. Hydroxyapatite suspension stability was investigated, in the pH range from 7 to 12, it was revealed that the most stable dispersion at pH 10.