Development of sustainable and ecofriendly metal ion scavenger for adsorbing Cu2+, Ni2+ and Zn2+ ions from the aqueous phase

Abstract

ABSTRACT In the present investigation, adsorption of Cu2+, Ni2+ and Zn2+ ions is carried out on the surface of novel composite made up of bentonite clay and red-ocher. The study of molecular dynamics through dimensionless numbers, Nk and proved that adsorption of Cu2+, Ni2+ and Zn2+ ions on the surface of composite was diffusion controlled. A deviation of 0.08% for Cu2+, 1.26% for Ni2+ and 0.53% for Zn2+ ions between experimental and artificial neural network model predicted values reflected that the back-propagation technique involving Levenberg-Marquardt algorithm was appropriate for the prediction of the output function. The physico-chemical characterization of composite indicated fluffy composite surface housing hydroxyl group, Si-O stretching and Si-O-Al vibration. These groups were due to aluminum-rich octahedral centers and Si-O bond stretching of silica and quartz. The X-ray diffractogram of composite depicted the presence of quartz, alumina, montmorillonite and hematite in the composite that played a significant role in adsorbing heavy metal ions. The Langmuir isotherm and pseudo-second-order kinetic model showed lower values of sum of square of residuals compared to other models. This showed that sorption of Cu2+, Ni2+ and Zn2+ ions followed monolayer coverage coupled with chemisorption mode. The composite possesses high adsorption capacity such as 61.86 mg/g for Cu2+ ions, 37.89 mg/g for Ni2+ ions and 10.48 mg/g for Zn2+ ions. The adsorption of metal ions onto composite surface was endothermic with increased randomness at the solid–liquid interface.