Assessment of the adsorption kinetics, equilibrium and thermodynamics for the potential removal of Ni²⁺ from aqueous solution using waste eggshell

Abstract

In this study, Ni²⁺ sorption onto the waste eggshell was investigated under different operational conditions. Results indicated that the eggshell could be successfully used to remove Ni²⁺ ions from the water. Quick sorption process reached to equilibrium in about 2 hours with maximum sorption at pH 7.0. Based on the experimental data, Langmuir isotherm model with the q_m value of 1.845 mg Ni²⁺/g eggshell was observed. The pseudo-second-order model provided the best correlation coefficient in comparison with other models. The calculated q_e values derived from the pseudo-second-order for sorption of Ni²⁺ ions were very close to the experimental (q_exp) values. Such thermodynamic parameters as ΔG°, ΔH°, and ΔS° were determined in order to predict the nature of adsorption. Results indicated that the adsorption of Ni²⁺ onto the eggshell was endothermically supported by the increasing adsorption of Ni²⁺ ions with temperature.

Keyword : adsorption isotherms, eggshell, nickel, thermodynamics