Oxidation-Induced and Hydrothermal-Assisted Template-Free Synthesis of Mesoporous CeO 2 for Adsorption of Acid Orange 7.

Hydrogen peroxide (H 2 O 2 ), an accessible and eco-friendly oxidant, was employed for the template-free hydrothermal synthesis of mesoporous CeO 2 based on a cerium carbonate precursor (Ce 2 (CO 3 ) 3 • x H 2 O). Its microstructure and physicochemical properties were characterized by XRD, TEM and N 2 sorption techniques. The formation of the CeO 2 phase with a porous structure was strongly dependent on the presence of H 2 O 2 , while the values of the BET surface area, pore diameter and pore volume of CeO 2 were generally related to the amount of H 2 O 2 in the template-free hydrothermal synthesis. The BET surface area and pore volume of the mesoporous CeO 2 synthesized hydrothermally at 180 °C with 10 mL H 2 O 2 were 112.8 m 2 /g and 0.1436 cm 3 /g, respectively. The adsorption process had basically finished within 30 min, and the maximum adsorption efficiency within 30 min was 99.8% for the mesoporous CeO 2 synthesized hydrothermally at 140 °C with 10 mL, when the initial AO7 concentration was 120 mg/L without pH preadjustment. The experimental data of AO7 adsorption were analyzed using the Langmuir and Freundlich isotherm modes. Moreover, the mesoporous CeO 2 synthesized at 140 °C with 10 mL H 2 O 2 was regenerated in successive adsorption-desorption cycles eight times without significant loss in adsorption capacity, suggesting that the as-synthesized mesoporous CeO 2 in this work was suitable as an adsorbent for the efficient adsorption of AO7 dye from an aqueous solution.