The effect of NaOH and KOH treatment on the behavior of CO32- and OH- groups in natural origin hydroxyapatite

Abstract Hydroxyapatite of natural origin differs from the synthetic one. It is non-stoichiometric, contains carbonate groups and some other trace elements. The organic matter was removed from the animal bones by their treatment in sodium or potassium hydroxide. In the present study the effect of NaOH and KOH treatment of different concentrations and for different times was observed. It has been found that the process of dissolution–precipitation occurs. It leads to the decreased specific surface area of the resulting powder and the increased crystallites sizes. The de-convoluted infrared spectra allowed us to state that the newly crystallized matter contains fewer carbonate groups and higher concentration of hydroxyl groups as compared to the starting material. So the material shifts towards the A-type HAp. Nevertheless, it can still be defined as the AB-type hydroxyapatite. The phenomena become more advanced with time of treatment and concentration of the treating reagent.