Abstract:
This study examines the application of poultry eggshell (PES) as a
source of calcium for the synthesis of hydroxyapatite (HA) via annealation. The
synthesized powder (poultry eggshell hydroxyapatite (PESHA)) was characterized
by X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron
microscopy (SEM), EDAX, and transmission electron microscopy (TEM)
analytical techniques. This powder was used for adsorptive removal of the
Reactive Yellow 4 (RY4) dye in a batch process. Results from morphological
analysis by SEM and TEM revealed that the microstructure of the apatite is made
up of needle−rod-like particles with the length of 15−60 nm, breadth of 4−6 nm,
and crystallite size of 86.32 nm. EDAX revealed that HA has Ca/P ratio of 1.63,
indicating a nonstoichiometric apatite, whereas XRD analysis presented it as a pure
monophasic hydroxyapatite powder. Fourier Transform Infrared (FTIR) spectroscopy indicated that the adsorption is due to the electrostatic interaction between
the functional groups of the dye and those on the apatite surface. The maximum
adsorption capacity (Qmax) of 127.9 mg g−1 was obtained for the adsorption process, whereas the pseudo-first-order model with R2 > 0.99 best described the adsorption mechanism. Furthermore, the thermodynamic studies revealed that the adsorption process was exothermic and spontaneous in nature with ΔH and ΔS values of 120.79 kJ mol−1 and 0.395 kJ mol−1 K−1, respectively. Thus, hydroxyapatite fabricated from the poultry waste of egg
