Adsorption of Cu2+ from aqueous solution onto iron oxide coated eggshell powder: Evaluation of equilibrium, isotherms, kinetics, and regeneration capacity

This study explored the adsorption behavior of Cu2+ onto iron oxide coated eggshell powder (IOESP) from aqueous solution. The effect of various operational parameters such as pH, contact time, initial adsorbate concentration, surfactant, and temperature on adsorption of Cu2+ ions was investigated using batch adsorption experiments. The optimum pH for Cu2+ adsorption was found to be 6.0. Kinetics of adsorption was found to follow the pseudo-second-order rate equation. The suitability of Langmuir and Freundlich adsorption models to the equilibrium data was investigated. The adsorption was well described by the Freundlich isotherm model indicating the presence of heterogeneous sites for Cu2+ adsorption. The adsorption of Cu2+ was increased in the presence of anionic surfactant (SDS) while cationic surfactant (CTAB) shows no significant change in adsorption capacity. Thermodynamic parameters showed that the adsorption of Cu2+ onto IOESP was feasible, spontaneous, and exothermic. Regeneration studies were performed using HCl, HCOOH, EDTA, and NaOH as eluting agent for Cu2+ desorption from saturated IOESP and the maximum regeneration was observed with HCl.