Adsorption of Acid Blue 121 dye on fish (Dicentrarchus labrax) scales, the extracted from fish scales and commercial hydroxyapatite: equilibrium, kinetic, thermodynamic, and characterization studies

Abstract

In this study, the adsorption of Acid Blue 121 (AB 121) on fish (Dicentrarchus labrax) scales (FS), extracted hydroxyapatite from FS (FHAp), low-cost, and environment-friendly adsorbent, and commercial hydroxyapatite (CHAp) was investigated in a batch system as a function of contact time, initial dye concentration, initial pH, adsorbent concentration, and temperature. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models were applied to the experimental equilibrium data and it was found that the experimental equilibrium data of AB 121 adsorption fitted well to the Langmuir isotherm model. The monolayer coverage capacities of FS and CHAp for AB 121 adsorption were found as 300.7 and 291.5 mg/g, respectively. It was observed that the pseudo-second-order kinetic model could be used for the prediction of studied adsorption processes kinetics. Both film diffusion and intraparticle diffusion contribute to the rate-limiting mechanism. The thermodynamic parameters showed that AB 121 adsorption on FS and CHAp was exothermic in nature. The Fourier transform infrared spectrometer, X-ray diffraction and scanning electron microscopy, energy dispersive X-ray analyzer and Brunauer, Emmet and Teller surface area analyzer were used for adsorbent characterization studies before and after dye treatment. And also, the reusability of FS was determined by desorption studies.