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Synthesis of zinc-aluminum mixed oxide/polyvinyl alcohol (ZnAl mixed oxide/PVA) and application in Pb(II) removal from aqueous solution

Abstract In this study one-pot synthesis of zinc-aluminum mixed oxide/polyvinyl alcohol (ZnAl mixed oxide/PVA) nanocomposite and its adsorption behavior for efficient removal of lead (II) ions from aqueous solution were investigated. The synthesized nanocomposite was characterized by X-ray diffraction (XDR), Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and Ultraviolet-visible spectroscopes (UV-Vis) to study structural, optical properties, morphology and elemental composition. Two characteristic reflections of ZnO and Zn6Al2O9 phases were shown by the XRD pattern of the nanocomposite. Due to PVA strongly caped the particles, the subsequent growth of the nanoparticle was prevented and estimated as 10.5 and 7.8 nm for ZnO and Zn6Al2O9 crystallites, respectively. The concentration of Pb(II) in a solution was investigated by Inductively coupled plasma - optical emission spectrometry (ICP-OES). The optimum pH for the uptake of Pb(II) on ZnAl mixed oxide/PVA was 5.0. The removal efficiency of Pb(II) reached up to ∼97% after 180 min when 0.03 g ZnAl mixed oxide/PVA was added in 10 mL Pb(II) solutions which the concentration was 331.4 mg/L (10-3 M) at the condition of neutral pH and 298 K. Pseudo-second-order kinetic model and Freundlich isotherm were found to be the most suitable models to define the adsorption mechanism in this process. Thermodynamic parameters like ΔH°, ΔS°, ΔG° and Ea of the adsorption of Pb(II) ions onto ZnAl mixed oxide/PVA are estimated -72.98, −0.222, −6.737 and 25.956 kJ/mol at the condition of neutral pH and 298 K. After 9 cycles the % removal of Pb(II) ions reduced to 63.177%. Graphical Abstract