Synthesis of α-MnO2 Nanomaterial from a Precursor γ-MnO2 : Characterization and Comparative Adsorption of Pb(II) and Fe(III)

alpha-MnO2 nanostructure was successfully synthesized via hydrothermal treatment of a precursor gamma-MnO2. Structure, morphology, and BET surface area were characterized using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), and Brunauer-Emmett-Teller nitrogen adsorption (BET-N-2 adsorption). Thermal analysis result showed that alpha-MnO2 nanorods were formed from gamma-MnO2 at 600 degrees C. In addition, Pb(II) and Fe(III) adsorptive properties were investigated in an optimal condition. Results showed that equilibrium adsorption was obtained after 60 minutes for Pb(II) at pH = 4.0 and 80 minutes for Fe(III) at pH = 3.5 with 240 rpm of shaking speed overall. Experimental data was analyzed using three models: Langmuir, Freundlich, and Sips. Adsorption capacities (q(m)) from the Langmuir isotherm models are 124.87mg/g for Pb(II) and 30.83mg/g for Fe(III). Along with the highest corelation coefficients, it is clear that the adsorption of Pb(II) and Fe(III) ions on alpha-MnO2 surface followed Sips model. Kinetic studies indicated that the uptake of Pb(II) and Fe(III) occurred in the pseudo-second-order model with two stages for Pb(II) and three stages for Fe(III).