Kinetics, equilibrium and thermodynamic of heavy metal sequestration unto mango seed biomass (Mangifera indica).

Abstract

This study deals with the evaluation of biosorptive removal of nickel (II) by Mangifera indica seed. FTIR was used to determine the functional groups on Mangifera indica responsible for adsorption. Experiments have been carried out to find the effect of various parameters such as pH, adsorbent dosage, contact time, and temperature on the adsorption performance for the removal of Ni(II) ions. The experimental data were analyzed with four sorption kinetic models: the pseudo-first order, pseudo-second order, intraparticle diffusion as well as the Boyd models. Results showed that the adsorption kinetics followed the pseudo-second order rate equation. The mechanism of reaction was film-diffusion controlled. Langmuir, Freundlich and Dubinin–Radushkevich (D–R)models were used to describe the adsorption of Ni(II) ions on Mangifera indica seed. Biosorption equilibrium was better described by the Freundlich model (R2 = 0.97). The monolayer biosoption capacity of Mangifera indica for Ni(II) ions concentration of 50 mg/L was 77.5 mg/g at 30 ± 1 oC. The thermodynamic parameters revealed that adsorption reaction using the Mangifera indica seed was spontaneous and endothermic for Ni(II) ions. The mean free energy, E, from the D-R, the ∆G and Ea values obtained showed that the adsorption process was physisorption. The present investigation showed that Mangifera indica can be utilized as a low cost and easily available biosorbent for Ni(II) ions removal.