Adsorption of CO2 on non-stoichiometric strontium–calcium hydroxyapatites

Abstract

Colloidal particles of homogeneous solid solutions of strontium and calcium hydroxyapatites (SrCaHAP) have been synthesized in different mole fractions, Sr/(Ca + Sr) ranging from 0 to 1. The crystallite size of the SrCaHAP particles obtained was a minimum around Sr/(Ca + Sr)= 0.3, whereas the specific surface area was maximum around the same Sr/(Ca + Sr). The morphology of the SrCaHAP particles became irregular as Sr/(Ca + Sr) increased up to 0.5. The irreversible adsorption of CO₂ per unit surface area was a minimum at (Ca + Sr)/P = 1.56, less than the stoichiometric value of 1.67. These results suggest that there are two kinds of irreversible adsorption site for CO₂ on SrCaHAP.