Structural and magnetic properties of ferric oxide-silica core-shell nanocomposite and its application for removal of cd (ii) ion
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2018
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Structural and magnetic properties of ferric oxide-silica core-shell nanocomposites were investigated for facile removal of Cd(II) ions from water. Silica (SiO2), ferric oxide (Fe2O3) nanoparticles, Fe2O3@SiO2 and SiO2@Fe2O3 coreshell nanocomposites were synthesized by modified Stober’s method, co-precipitation method, surfactant assisted sonication method and surfacant assisted direct precipitation of SiO2 on the surface of Fe2O3 NPs respectively. Techniques viz. X-ray diffractiion pattern (XRD), Vibrating sample magnetometer (VSM), Brunauer-Emmett-Teller (BET), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and FT-IR spectroscopy were invastigated. The effect of different reaction parameters including adsorbent dose, temperature, contact time, pH, initial metal ion concentration of Cd(II) was studied. Optimum pH for adsorption was 6. With the increase of temperature, the removal efficiency of synthesized adsorbents for Cd(II) ions increased up to 55ºC and then decreased. Values of ΔGo found to be negative for all the adsorbents, indicating spontaneous nature of adsorption process. While, positive values of ΔH and ΔS for all adsorbents indicated the endothermic nature of adsorption process. The trend for the percentage removal of Cd(II) in the descending order was Fe2O3@SiO2 > Fe2O3 > SiO2@Fe2O3 > SiO2. The trend for the fitting of adsorption isotherms in descending order was Freundlich > Langmuir > Tempkin > D-R isotherms. The adsorption followed pseudo second order kinetics. The advantage of nanocomposites is enhancement of adsorption potential due to presence of Fe2O3 along with SiO2. The results signified that core-shell reversal is effective way of tailoring the properties of nanocomposites.
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