Ceria and cerium-based mixed oxides as ozonation catalysts

Ceria (CeO2) and cerium-based mixed oxides (Ce–Sm, Ce–La and Ce–Zr with different compositions) were prepared by the precipitation method from aqueous solutions of nitrate precursors. The materials synthesized were tested as catalysts in the ozonation of oxalic acid, aniline and the textile dye C. I. Reactive Blue 5.Different performances were obtained depending on the type of organic compound and catalyst involved. In the case of oxalic acid, cerium–zirconium catalysts with more zirconium presented the best catalytic activities, allowing a total removal after 3 h of reaction. The good performance of these samples was justified by the increase of Ce(III) species on their surfaces. In the catalytic ozonation of aniline, the highest mineralization degree was achieved with CeO2 and Ce0.75Zr0.25O2, the latter being the sample with the largest amount of oxygen vacancies on its structure. All the prepared catalysts significantly improved the mineralization rate in the ozonation of the dye solution relatively to single ozonation (no catalyst). By itself, adsorption on the surface of catalysts is not relevant in the removal of organic compounds.

► Ceria and cerium-based mixed oxides were tested as catalyst in the ozonation of organic pollutants.
► For oxalic acid the catalytic activity increases with the increase of Ce(III) on the surface.
► The surface oxygen vacancies play an important role in the mineralization of aniline.
► All catalysts allowed a complete or near complete mineralization of the dye solution.