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

Mishra, Prashant Kumar, Gahlyan, Parveen, Kumar, Rakesh, Rai, Pramod Kumar
ACS sustainable chemistry & engineering 2018 v.6 no.8 pp. 10668-10678
adsorbents, adsorption, ambient temperature, arsenic, ceric oxide, cerium, iron, iron oxides, magnetism, metal ions, nanoparticles, oxidation, oxygen, pH, reflectance spectroscopy, scanning electron microscopy, toxicity, transmission electron microscopy, ultrasonics
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 Fm3̅m 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.