Oak wood ash/GO/Fe3O4 adsorption efficiencies for cadmium and lead removal from aqueous solution: Kinetics, equilibrium and thermodynamic evaluation

Abstract

Magnetic Oak wood ash/Graphene oxide (Ash/GO/Fe3O4) nanocomposites were designed as a high potent adsorbent in the removal of toxic heavy metals such as Lead (Pb(II)) and Cadmium (Cd(II)) ions from aquatic medium. Characterization of Ash/GO/Fe3O4 samples was carried out using FESEM, TEM, EDX mapping, BET/BJH, XRD, FTIR, and VSM methods. The obtained results confirmed the successful synthesis of Ash/GO/Fe3O4 nanocomposites. In the adsorption process, almost complete adsorption efficiency of produced Ash/GO/Fe3O4 nanocomposite was attained under the optimized conditions (99.67% and 98.68% for Pb(II) and Cd(II) adsorption, respectively). The modeling results of kinetics indicated that the mechanism of Pb(II) and Cd(II) adsorption process well fitted by pseudo-second order equation with a high regression coefficient (99.67%). In addition, the equilibrium data were described well by non-linear Langmuir model with the highest adsorption capacity of 47.16 mg/g and 43.66 mg/g for Pb(II) and Cd(II) ions, respectively, which prove the effective adsorption ability of the magnetic nanocomposite. The spontaneous and exothermic nature of adsorption process was confirmed through thermodynamics analyses. The reusability of synthesized Ash/GO/Fe3O4 nanocomposites were demonstrated with negligible decrease in adsorption and high stability up to 8 repetitive adsorption cycles. The mechanism of Pb(II) and Cd(II) adsorption on the Ash/GO/Fe3O4 nanocomposite was assessed.