Author: S. K. Reddy, R. U. Devi, K. Hossain, and J. Swaraj

DOI: http://doi.org/10.31788/RJC.2026.1919528

This study examined the potential of activated carbons of Zirconium-Hydroxyapatite (Zr-HAP) produced frombiowaste, that as fish bones, as an effective adsorbent material for the uptake of Rhodamine B, which is a xenobioticdye. A hydrothermal method is used to synthesize fish bone waste-based Zr-HAP activated carbons. Thecharacterisation of activated carbons' properties, specifically XRD, EDS, FTIR, SEM and TEM, was conducted. Theadsorption efficiency of Rhodamine B correlates with the initial increase of Activated carbon dosage, reachingssaturation plateau at 40 ppm, with 100% removal observed at an optimal pH of 5 - 6. As the dye concentrationincreased, adsorption efficacy decreased, indicating monolayer adsorption at lower concentrations. Isothermanalysissuggested that the Langmuir model best described the process (with R 2 = 0.969), indicating homogenous adsorption. Kinetic modelling confirmed chemisorption with a pseudosecond-order mechanism being predominant. Thermodynamic analysis revealed the exothermic and spontaneous nature of the adsorption process. These studyoutcomes demonstrate that fish bone-based Zr-HAP activated carbon can be effectively utilised as an adsorbent for the removal of Rhodamine B in a sustainable process.

Keywords: Adsorption, Hydroxyapatite, Zirconium, Activated Carbons, Langmuir, and Kinetics