Apatite nucleation on silica surface: A zeta potential approach

zeta potential measurements on pure silica, prepared by the sol-gel method from tetraethoxysilane under acidic conditions, are reported in different s uspensions. Wa ter suspensions and suspensions containing calcium or phosph ate ions with and without NaCl were tested. zeta potential measurements wer e carried out as a function of the pH and ion concentration, Also, calcium and phosphate adsorption on silica was determined experimentally. The resul ts of zeta potential and adsorption measurements suggest that both calcium and phosphate ions can be adsorbed on the silica surface; however, calcium adsorption is stronger than phosphate adsorption. When calcium and sodium i ons are present in the suspension, calcium adsorption decreases. It seems t hat certain sites on the silica surface are specific for calcium adsorption . (C) 2001 John Wiley & Sons, Inc.