Apatite-Silica Gel Composite Materials Prepared by a New Alternate Soaking Process

Abstract

Novel apatite/silica composite materials were synthesized by modifying the surface of silica gel beads or plates with apatite. An “alternate soaking” process, which involves alternate soaking in a CaCl₂/tris-HCl aqueous solution (pH 7.4) and a Na₂HPO₄ aqueous solution, was utilized to prepare a composite of silica gel and apatite. The characteristics of apatite formed on the surface of silica gel have been studied using X-ray diffraction, Fourier-transform infrared spectrophotometry (FT-IR) and scanning electron microscopy (SEM). Data clearly showed surface modification of silica with the crystalline apatite. Pore volume and specific total surface area, which were measured using nitrogen gas adsorption apparatus, were decreased after apatite deposition on the surface of silica gel beads, whereas the external surface area was increased drastically. The alternate soaking process made it possible to prepare apatite/silica gel composites in a remarkably short period of time, i.e. several hours.