Adsorption of Cr(VI) on Ultrafine Al2O3-doped MnFe2O4 nanocomposite surface: Experimental and theoretical study using double-layer modeling

The synthesis of Al2O3-doped MnFe2O4 nanocomposite (Al2O3@MnFe2O4) for the adsorption of Cr(VI) ions from an aqueous solution is reported. FE-SEM, EDAX, XRD and FTIR are performed to characterize the Al2O3@MnFe2O4 nanocomposite. The kinetic data were analyzed using pseudo-first and pseudo-second-order kinetic models. The adsorption data is fitted well with the pseudo-second-order adsorption model for the adsorption of Cr(VI) ions. This demonstrated that the equilibrium adsorption data is better fitted with the Langmuir isotherm model when compared to the Freundlich model. The Q(max) value was found to be 158.73 mg/g. This mathematical physics model was used to demonstrate the number of bound Cr(VI) ions and the saturated adsorption potential at various temperatures. The orientation and significance of the proposed functional groups in the nanocomposite during the adsorption of Cr(VI) ions, including their thermodynamic parameters, have been defined using statistical physics models. For the Cr(IV)-Al2O3@MnFe2O4 adsorption method, parameter n was calculated and found to decrease (from 0.364 to 0.358), confirming its temperature-dependence. The estimation of these parameters shows that all of the Cr(IV) ions on the adsorbent surface have a horizontal adsorption orientation.