Augmentation of photocatalytic activity of nano-crystallite hydroxyapatite by fluoride doping

Abstract

In this study, we synthesized hydroxyapatite (HAp) with added dopants and utilized it for the degradation of a model dye, Congo red, Congo red in an aqueous solution. In particular, to enhance photocatalytic activity, the HAp nanostructure was engineered via doping with different percentages (0.25 %, 0.5 %, 1 %, and 2 %) of fluoride ions. However, this newly developed fluoride-doped HAp (F-HAp) was characterized by several instrumental techniques, e.g. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), and UV–vis spectrometry. Crystallographic characterization of the synthesized pure and F-doped HAp was performed from the XRD data. On the other hand, the efficiency of F-HAp as a photocatalyst was investigated via the halogen light-induced degradation of Congo red. F-HAp nano-photocatalyst effectively degraded Congo red in aqueous solution and process variables such as pH, reaction time, doses of catalyst, source of photons (sunlight degradation), temperature, and Congo red concentration were optimized. Compared to pure HAp, altering the percentages of dopant ions within the HAp structure resulted in an enhanced photocatalytic performance for the degradation of Congo red dye across all tested conditions. It was noted that under specific conditions, such as a pH of 7 and 150 min of halogen lamp irradiation, employing a 0.1 g dosage of 0.25 % F-HAp led to nearly 99 % degradation of a 20 ppm Congo red solution. Notably, this level of degradation surpassed that achieved with pure HAp.