Effect of sulfate ion on silicate ion substitution on hydroxyapatite

Author(s): N.Y.Mostafa, A.N.Al-Saifi, H.A.Azab, M.Kamel, M.A.Raizk

Several hydroxyapatite powders were prepared by wet chemical precipitation route at 25C in presence of different concentration of silicate and sulfate. The powderswere characterized using chemical analysis, SEM,XRD and FTIR spectroscopy. The substitution of sulfate ion in the structure of HAP raised silicate substitution up to 9.9 % wt. Increasing silicate and sulfate ions substitutions are associated with increasing carbonate ion substitutions for phosphates and vacancies in the OH– site. Silicate and sulfate substitution took place via three charge compensation mechanism acting simultaneously. The first is; SiO4 4– group substitute one PO4 3– group and vacancy formin the OH- site. The second is; SiO4 4- and SO4 2– groups substitute two PO4 3– groups. The third is; SiO4 4- and CO3 2– groups substitute two PO4 3– groups.

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