The removal of Cr (III) and Co (II) ions from aqueous solution by two mechanisms using a new sorbent (alumina nanoparticles immobilized zeolite) - Equilibrium, kinetic and thermodynamic studies

•Using a new dual function sorbent for the applicable removal of Cr (III) and Co (II) ions•Toxic metal ion removal by adsorption & ion exchange mechanisms separately & simultaneously•Isotherm, kinetic and thermodynamic studies of the Cr (III) and Co (II) removal•Comparison of the metal ion removal behavior by different mechanisms

The removal of Cr (III) and Co (II) from various samples of ionic solutions was investigated using several sorbents such as alumina nanoparticles (Al2O3 NPs), NaX zeolite granules and a new sorbent: alumina nanoparticles immobilized zeolite (ANIZ), in batch mode. The effects of various operating parameters were studied in order to optimize the removal conditions. Results showed that the removal capacity of zeolite has been significantly improved (Cr (III): 31.76%, Co (II): 17.2%) after the immobilization of Al2O3 NPs. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) equations were examined to describe the isotherm models and their constants were evaluated. The kinetic data were analyzed using Pseudo first order, Pseudo second order, Elovich and intraparticle diffusion models. The equilibrium data showed excellent correlation for both Langmuir and Freundlich isotherm models and the Pseudo second-order model was fitted to experimental results better than the other kinetic models. Thermodynamic analyses of the equilibrium data suggested that the removal reactions were spontaneous [− ΔG°, kJ·mol− 1 = 29.37 to 43.69 for Cr (III); and 33.54. to 41.61 for Co (II)] and the spontaneity increased with increasing temperature.