Properties of hydroxyapatite from tilapia (Oreochromis niloticus) bones: An approach towards its potential use as a dye adsorbent

The properties of hydroxyapatite (HAp) obtained from tilapia (Oreochromis niloticus) bones and its potential use as a dye adsorbent using methyl orange (MO) as a model dye were evaluated. HAp was produced by the calcination of dried tilapia bones at 900 °C for 4 h. Then, HAp was characterized using thermogravimetric (TGA) and differential thermogravimetric (dTG) analyses, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), x-ray diffraction (XRD), among others. The HAp obtained was used for MO dye adsorption in a batch process. The yield of HAp was 51.6%. FTIR showed characteristic bands of functional groups of HAp [OH- and (PO4)3-]. FESEM images showed HAp with different morphologies and a porous surface. The EDS analysis indicated the presence of calcium and phosphorus with an atomic ratio of Ca/P of 1.60, TEM images revealed the formation of agglomerates and an average particle size of 655.1 nm. HAp and β-tricalcium phosphate (β-TCP) phases were identified through XRD. The HAp point of zero charge (pHpzc) was 9.7 indicating a possible adsorption of anionic dyes at pH< pHpzc and cationic dyes at pH> pHpzc. The HAp was able to successfully adsorb 82.6% of MO dye from aqueous solution. These findings demonstrated that the HAp obtained from tilapia (O. niloticus) bones possesses suitable properties to be used as a potential material to remove dyes.