A flash photolysis study of the photodegradation of H2O2 in aqueous solutions at different temperatures

FERNANDO S. GARCÍA EINSCHLAG; MARIO R. FÉLIZ; ALBERTO L. CAPPARELLI

Foz de Iguazú, Brasil

Congreso; Eighth Inter-American PhotoChemical Society Conference; 1996

            Flash photolysis on H2O2 has been used as source of OH radicals in oxidation processes (1)-(3). However, mostly the available information comes from pulse radiolysis studies at 23°C (4). The effect of the temperature is not reported in the literature, and the analysis of the rates in oxidation processes in those system are confined to the initial rate always in presence of the organic compound.             In this communication, the flash photolysis of hydrogen peroxide at different temperature (20 to 50 °C) and pH (2 to 7) is reported.             As the global kinetic analysis is rather complex, the experimental traces show some scattering and the equations associated with the possible mechanism are rather cumbersome, a general fitting program was developed. This program showed to be quite useful for analizing complex reactions.             Samples of hydrogen peroxide of similar concentration as those reported in this paper were analyzed in a total organic carbon and ionic chromatography equipments. No organic matter or ions were detected under those conditions compatible with our experimental conditions.             Temperature and pH affect strongly the kinetics of this reaction. From the observed rate constants, global activation energies can be obtained. References (1) A.D. Nadezhim & H.B. Dunford, Can. J. Chem., 57, 3017 (1979) (2) A.D. Nadezhim & H.B. Dunford, J. Phys. Chem., 83, 1957 (1979) (3) B. Bielski & D. Cabelli, in Active Oxygen in Chemistry, C. Foote, J. Selverstone Valentine, A. Greenberg and J. Liebman, Ed., Search Series, Vol. 2, Ch. 3, pp 66, 1995, Chapman Hall, London and references therin. (4) B. Bielski, D. Cabelli and R, Arudi, J. Phys. Chem. Ref. Data, 14, 1041 (1985)