Vacuum-UV-photolysis of aqueous solutions of citric and gallic acids.

N. QUICI; M. I. LITTER; A. M. BRAUN; E. OLIVEROS

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY

ELSEVIER SCIENCE SA

Lugar: Lausanne; Año: 2008 vol. 197 p. 306 - 312

1010-6030

The vacuum-UV- (VUV-) photolysis of water is one of the Advanced Oxidation Processes (AOP) based on the production of hydroxyl  radicals (HO·) that can be applied to the degradation of organic pollutants in aqueous systems. The kinetics of the VUV-photolyses of aqueous solutions of citric acid (1) or gallic acid (2) were investigated in the presence or absence of dissolved molecular oxygen (O2) and under different pH conditions. In the case of 1, the rate of consumption of the substrate was faster at pH 3.4 than in alkaline solution (pH 11), whereas, in the case of 2, the variation of pH (2.5 to 7.5) did not affect the course of the reaction. Unexpectedly, the rates of depletion of both 1 and 2 decreased in the absence of O2, this effect being much more pronounced in the case of 2. In order to explain these results, possible reaction pathways for the degradation of 1 and 2 are proposed, and the roles of the oxidizing (HO·) and reducing (H· and e-aq) species produced by the VUV-photolysis of water are discussed.