Rapid Removal of Zinc(II) from Aqueous Solutions Using a Mesoporous Activated Carbon Prepared from Agricultural Waste

Abstract

A low-cost activated carbon (XSBLAC) prepared from <i>Xanthoceras</i><i>Sorbifolia</i><i>Bunge</i><i>hull</i> via chemical activation was investigated to determine its adsorption and desorption properties for zinc(II) ions from aqueous solutions. XSBLAC was characterized based on its N₂-adsorption/desorption isotherm, EDX, XRD, SEM and FTIR results. An adsorption study was conducted in a series of experiments to optimize the process variables for zinc(II) removal using XSBLAC. Modeling the adsorption kinetics indicated good agreement between the experimental data and the pseudo-second-order kinetic model. The Langmuir equilibrium isotherm fit the experimental data reasonably well. The calculated enthalpy (Δ<i>H</i>⁰), entropy (Δ<i>S</i>⁰) and Gibbs free energy (Δ<i>G</i>⁰) values revealed the endothermic and spontaneous nature of the adsorption process. HNO₃ displayed the best desorption performance. The adsorption mechanism was investigated in detail through FTIR and SEM/EDX spectroscopic analyses. The results suggested that XSBLAC is a potential biosorbent for removing zinc(II) from aqueous solutions.