A novel ceria-activated carbon composite for the catalytic ozonation of carboxylic acids

Ceria (Ce-O) and a novel ceria-activated carbon composite (ACO-Ce-O) were prepared and tested as catalysts in the ozonation of two selected carboxylic acids, oxalic acid and oxamic acid, at acid pH. Ce-O showed an interesting catalytic effect, especially in the ozonation of oxalic acid. A strong synergic effect was observed for the ACO-Ce-O composite in the case of oxalic acid, leading to the best results in the mineralization of this compound. Both materials enhanced the removal of oxamic acid relatively to single ozonation. The Ce-O catalytic ozonation was shown to comprise bulk oxidation reactions occurring via HO center dot radicals. In the case of the composite, both surface and bulk reactions are supposed to occur. Some considerations about the mechanisms are presented. (C) 2008 Elsevier B.V. All rights reserved.