Aero-Gel Based Cerium Doped Iron Oxide Solid Solution for Ultrafast Removal of Arsenic

A solid solution of aero-gel based cerium doped iron oxide nanoparticles has been utilized for the first time for ultrasonic wave assisted adsorptive removal of arsenic from aqueous medium. The FE-SEM and HR-TEM images revealed a novel morphology of hollow architectures with irregular distribution in sizes in which the particles are interconnected with each other in a long-range network. The HR-XRD analysis indicated the cubic fluorite type structure with <i>Fm</i>3̅<i>m</i> space group which is retained even after adsorption of As­(III). The Raman study and Lebail refinement confirmed the formation of solid solution of Fe and Ce oxide nanoparticles. The room temperature ferromagnetism was observed for CeO₂ NPs (Ms 0.0209 emu g^–1) which is attributed to higher concentration of oxygen vacancies and increased (Ms 0.0287 emu g^–1) after doping of iron. The adsorption pattern of As­(III) is well-defined by Redlich–Peterson isotherm while the adsorption is governed by pseudo-second-order kinetics. The HR-XPS and diffuse reflectance spectroscopy revealed the formation of variable oxidation state of metal ions which facilitate the oxidation of As­(III) (more toxic) to As­(V) (less toxic) during adsorption process. The effective removal of arsenic (more than 80%) was observed within 2.5 min of initial adsorption process and approximately 99% removal was achieved within 10 min of adsorption. The adsorption capacity of our best adsorbent was found to be 263 mg g^–1. The effect of pH and interfering ions on adsorption capacities of synthesized adsorbents revealed its efficacy over the wide range of pH