The crystal structures of Pb2+ ion-exchanged hydroxyapatite (OHAp), chlorapatite (ClAp), and fluorapatite (FAp) in aqueous solutions with low pH value of 3.0 or 4.0 have been investigated by X-ray powder pattern-fitting methods. The site occupancy factors of Pb atoms for the M1 (column site) and M2 sites were determined to be 0.72 and 0.77 for Pb7.5Ca2.5OHAp, 0.69 and 0.86 for Pb7.9Ca2.1ClAp, and 0.60 and 0.52 for Pb5.5Ca4.5FAp, respectively. These results imply that Ca2+ ions in calcium hydroxyapatite are exchanged for Pb2+ ions in acidic aqueous solution regardless of whether they occupy M1 or M2 sites.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry