Comparative studies on structural, magnetic and adsorptive properties of fused Fe2O3 @ SiO2 and rattle shapedSiO2@Fe2O3nanospheres with reversal of core-shell

Synthesis of core-shell nanocomposites is an important domain due to their applications as nanoadsorbents for heavy metal ions. In the present work, rattle type SiO2@Fe2O3 core-shell nanospheres were synthesized by surfactant assisted direct precipitation of SiO2 on Fe2O3 nanopartides. Whereas, fused magnetic nanospheres encapsulating mesoporous silica cores i.e. Fe2O3@SiO2 were formed by sonication method. Different techniques viz. SEM-EDX, TEM, XRD, BET and VSM were used for the confirmation of structure, crystallinity, surface morphology and magnetic properties of nanospheres. Effect of pH, contact time, adsorbent dose and temperature on Cd(II) adsorption was evaluated. The experimental data was fitted using Langmuir, Freundlich and D-R isotherm models. Monolayer adsorption efficiency (q(m)) for Fe2O3@SiO2 (769.0 mgg(-1)) was higher than SiO2@Fe2O3 (370.0 mgg(-1)) nanospheres, signifying better adsorption of Fe2O3@SiO2. The results confirmed that the reversal of core-shell can play an important role to effectively tune the properties of Fe2O3-SiO2 nanospheres for efficient removal of heavy metal ions.