Effect of chitosan concentration on hydroxyapatite/chitosan composite synthesis using the in-situ method as a dye adsorbent

Abstract

Hydroxyapatite (HAp) is a versatile material with wide-ranging applications, including its utility as an adsorbent. However, its brittleness and limited adsorption capacity pose challenges, prompting the incorporation of chitosan (CTS) fillers to enhance mechanical strength and adsorption properties. The hydroxyapatite/chitosan (HAp/CTS) composite was synthesized via the in-situ method, utilizing natural sources such as calcium ions from cuttlefish bones and chitosan extracted from shrimp shells. Various chitosan concentrations (10, 20, 30, 40, and 50 wt%) were explored in the synthesis process, with the optimal adsorption of Rhodamine B dye observed at a 30% concentration, yielding 0.1832 mg/g. Validation of the HAp/CTS composite synthesis was achieved through X-ray diffraction, revealing the presence of CTS at a new peak at 2θ of 19.23°, while infrared spectroscopy confirmed absorption bands for both HAp and CTS. Additionally, scanning electron microscopy-energy dipersive spectroscopy (SEM-EDS) investigations revealed irregular shapes with agglomeration, resulting in a Ca/P ratio of 1.80 for the HAp/CTS composite. The HAp/CTS-30% composite demonstrated efficient Rhodamine B dye adsorption following the Freundlich isotherm equation, pseudo-second-order adsorption kinetics, and exhibited good reusability. These findings suggest that the HAp/CTS composite could serve as a promising, cost-effective solution for treating industrial wastewater.