Kinetic, Equilibrium, and Thermodynamic Analyses of Ni(II) Biosorption from Aqueous Solution by Acorn Shell of Quercus crassipes

Exposure to divalent nickel [Ni(II)] poses a significant risk to human health. The present study was conducted to evaluate the biosorption capacity of acorn shell of Quercus crassipes Humb. & Bonpl. (QCS) for removal of Ni(II) ions from aqueous solutions in terms of kinetics, equilibrium, and thermodynamics. Batch biosorption studies showed that the Ni(II) biosorption behavior of QCS is strongly dependent on solution pH, shaking contact time, initial Ni(II) concentration, and temperature. Specifically, Ni(II) biosorption was found to increase with increasing solution pH, contact time, initial Ni(II) concentration, and temperature. Modeling of the Ni(II) biosorption kinetic and equilibrium data showed that the best agreement of experimental data was achieved with the pseudo-second-order kinetics model and the Freundlich isotherm model, respectively. The calculated thermodynamic parameters indicated that the Ni(II) biosorption process was endothermic, non-spontaneous, and chemical in nature. Fourier-transform infrared (FTIR) spectroscopy analysis showed that acidic functional groups, namely hydroxyl, carbonyl, and carboxyl functional groups, present on the QCS surface are likely to be involved in the biosorption of Ni(II) ions. The performance of QCS was compared with those of other reported biosorbents in terms of the efficiency of Ni(II) removal from aqueous solutions, revealing that QCS is highly effective in terms of its biosorption capacity. These findings indicate that QCS can be used as a low-cost, highly effective, and environmentally friendly alternative biosorbent for the detoxification of Ni(II)-contaminated water and wastewater.