In this article, the biosorption of Holmium(III) from aqueous solution was carried out using both raw and acid-treated bark powder of Mangifera indica as bio-sorbents and the results are being compared. Batch experiments were conducted by varying different reaction parameters such as metal concentration, biomass dosage, pH of the metal solution and contact time. The results showed that the acid-treated biomass exhibited higher percentage removal of the metal ion Ho(III) i.e. 93.44% than the untreated bark powder using two times lesser amount of treated bark powder than the untreated one. Kinetics, isotherm and thermodynamic studies of adsorption were carried out. Kinetics of the adsorption process follows the linear form of a pseudo-second-order model. The negative values of Gibbs free energy change (ΔG ◦) indicate the spontaneity of the adsorption process and the positive value of enthalpy change (ΔH ◦) suggests it as an endothermic process. Out of four isotherm models, the equilibrium data were well described by Langmuir adsorption isotherm conforming monolayer coverage. The results suggested that acid-treated bark powder of M. indica can be used as a cost-effective and efficient bio-adsorbent for the adsorption of Holmium(III).
Keywords: Biosorption; holmium(III); isotherms; kinetics; thermodynamics.