Photocatalytic degradation of citric acid under different conditions: TiO2 heterogeneous photocatalysis against homogeneous photolytic processes promoted by Fe(III) and H2O2.

N. QUICI; M.E. MORGADA; R. T. GETTAR; M. BOLTE; M. I. LITTER

APPLIED CATALYSIS B-ENVIRONMENTAL

ELSEVIER SCIENCE BV

Lugar: aMSTERDAM; Año: 2007 vol. 71 p. 117 - 124

0926-3373

Degradation of citric acid (Cit) at relatively high concentrations by photocatalysis over TiO2 under air bubbling and near UV-light was testedunder different conditions. The reaction was improved by addition of H2O2, Fe(III) or both. Minor amounts of H2O2 were effective to enhance theoxidation and the mineralization. H2O2 addition impacts more on the initial rate, while the effect of Fe(III) is more important after prolongedirradiation. The kinetic profiles were analyzed and compared, and the best ratio of reagents was found (1:1:1 H2O2/Cit/Fe molar ratio). However, alower amount of Fe (1:1:0.2 H2O2/Cit/Fe ratio) was also effective. Similar experiments under the optimal conditions in the absence of TiO2 wereperformed for comparison. When both H2O2 and Fe(III) were present, the behavior with and without TiO2 was very similar. So far, 3-oxoglutaricacid was detected as a reaction intermediate. A mechanistic analysis is initiated to explain some features of these complex systems.