Furthermore, the thermodynamic studies revealed that the adsorption process was exothermic and spontaneous in nature with Δ H and Δ S values of 120.79 kJ mol –1 and 0.395 kJ mol –1 K –1, respectively. The maximum adsorption capacity ( Q max) of 127.9 mg g –1 was obtained for the adsorption process, whereas the pseudo-first-order model with R 2 > 0.99 best described the adsorption mechanism.

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. 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. 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. This powder was used for adsorptive removal of the Reactive Yellow 4 (RY4) dye in a batch process. 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 study examines the application of poultry eggshell (PES) as a source of calcium for the synthesis of hydroxyapatite (HA) via annealation.

Thermo calc 2003p download yahoo