Magnetic oxide nanoparticles (Fe3O4) impregnated bentonite clay as a potential adsorbent for Cr(III) adsorption

This paper presents the adsorption of Cr(III)from aqueous solutions using the magnetic oxide impregnated bentonite clay. Results of the study suggested that Fe3O4 -Bentonite have excellent sorption potential in removing Cr(III) by conventional adsorption mechanisms. The characterization of impregnated sorbent was made by SEM, XRD, UV–vis and FTIR spectroscopy and salt addition methods. The effect of contact time, pH, metal concentration and dosage amount on the adsorption efficiency were investigated. The results showed that the adsorption capability for the Cr(III) increased by increasing the contact time and initial pH of the solution. The equilibrium data was evaluated by Langmuir, Freundlich and Dubinin-Radushkevich models to determine the nature of adsorption. Maximum capacity for Cr(III) was found 1.27 mmol g−1 at temperature of 283 K. Three kinetic models, Film, Particle, Intra-particle diffusion models and pseudo first order were applied to kinetic data to observe the reaction mechanism. The lower activation energy (less than 42 kJ mol−1) proved the diffusional and physical nature of metal sorption on magnetic sorbent. Thermodynamics parameters indicated the endothermic and spontaneous nature of the sorption process with entropical changes at solid-liquid interface. Moreover, Fe3O4 -Bentonite adsorbent was also regenerated and reused for successful recovery.