Ammonium hydrogen difluoride induced fluorination of hydroxyapatite

Ammonium hydrogen difluoride (NH4HF2) was used as a fluorinating agent for the fluorination of hydroxyapatite. The process was carried out at room temperature by pH cycle method, at 80 °C by reflux method and at 900 °C by solid state reaction. The products obtained in all the three methods were analyzed by powder XRD and FT-IR techniques to confirm fluorination. FT-IR spectra showed the decrease in the intensity of ‘OH’ stretching band at 3571 cm−1 and complete disappearance of ‘OH’ bending band at 632 cm−1. Appearance of a new peak at around 740 cm−1 (due to the formation of .H-F. bond) was observed in all the spectra. Similarly, powder XRD patterns exhibited higher angle shift in 2θ values of high intense peaks associated with (300), (112) and (211) planes when compared to parent hydroxyapatite. Both the structural and spectroscopic analyses confirmed partial fluorination of hydroxyapatite.