Hydrogen peroxide formation and decay in γ-irradiated clay water

The mechanism of the radiolytic formation and disappearance of hydrogen peroxide in aerated clay water was studied. The yield of H₂O₂ formation in clay water in an air atmosphere is equal to 0.25 μmol J^-1. When initially present in the solution, hydrogen peroxide disappears with a yield dependent upon the concentration and the dose rate. In both cases a steady state is reached dependent on the dose rate. In order to define more precisely the role of OH free radicals in this process, the reaction of these free radicals in clay water was studied by pulse radiolysis. As expected, OH is scavenged by different solutes, therefore, it cannot react with hydrogen peroxide. A kinetic scheme based upon these results is proposed. Using a minimal equation set (nine equations), it is possible to simulate the [H₂O₂] evolution with a very good accuracy, for doses going up to 20,000 Gy. It is also demonstrated that the reaction of H₂ with OH does not occur in such conditions, which is consistent with the accumulation of dihydrogen during the radiolysis of ground water.