Hydrogen peroxide formation during radiolysis of aerated aqueous solutions of organic molecules

Abstract

A large number of aromatic molecules were irradiated in 10−4moldm−3 concentration air-saturated aqueous solutions; the hydrogen peroxide production was followed. H2O2 formed with an initial yield of 2.5–3.5×10−7molJ−1, the concentration had a maximum (∼3×10−4moldm−3) due to the competition between the formation and decay. The H2O2 concentration increased with the dose rate in purified water samples, here the •OH+•OH reaction dominated in H2O2 production. In the presence of aromatic compounds the H2O2 concentration decreased with the increasing dose rate: the main source of H2O2 was the termination reaction of the O2•−/HO2• pair. This pair formed in the eaq−+ O2 and H•+O2 reactions and also in elimination from organic peroxy radicals. The dose rate dependence was attributed to the changes in the ratios of the different formation ways of H2O2. The main H2O2 consuming process was suggested to be the eaq−+H2O2 reaction. In the present study the Cu(II)/phenanthroline H2O2 test was used for concentration determination. The test was found to be applicable in wide concentration range, but it provided false results when the solutions contained phenol type compounds. To overcome such interferences the removal of these compounds by liquid-liquid extraction was suggested.