Clay Minerals Functionalized by Magnetite (Fe3O4) Nanoparticles as Solid Platform for Removal of Chromium (VI) from Water: Characterization, Kinetics, Thermodynamics, Analytical Utility and Reusability Studies

Abstract

A new protocol for the extraction of chromium (VI) from water is proposed. The established method was based upon retention of chromium (VI) species from aqueous HCl solution (pH = 0.0-2.0) as ion associate of chlorochromate [CrO3Cl]- aq anions onto the clay minerals (CMs) functionalized by magnetite (Fe3O4) nanoparticles (NPs) as solid platform (Fe3O4NPs/CMs). The nanocomposite Fe3O4NPs/CMs was characterized using various instrumental techniques. The nanocomposite enhanced chromium (VI) uptake via the synergic effect of the modified surface area and surface-modified groups, solvent extraction based ion exchange, and electrostatic adsorption. Chromium (VI) sorption was fast and fitted with pseudo-second order with a rate constant of 0.078 min-1 and half-life time (t1/2) of 1.2±0.04 min. The positive and negative values of the enthalpy (ΔH =3.08 kJmol-1) and the Gibbs free energy (ΔG = -5.539 KJmol-1) indicate endothermic, spontaneous, and physical in nature of chromium (VI) uptake and the binding of the [CrO3Cl]- aq onto the nanocomposites was proceeded via electrostatic interactions. Sorbent packed column was tested for chromium (VI) uptake from water, subsequently recovered with NaOH (1.0 mol L-1), and analyzed. Sorbent packed column was reused 3-4 times towards chromium (VI) in water. The sorbent could easily be regenerated with NaOH.