Interaction of hydrogen with radiolysis products in NaCl solution — comparing pulse radiolysis experiments with simulations

In pulse radiolysis experiments at 22 °C production and decay of Cl2− radicals are studied in 0.1 and 1.0 mol dm−3 NaCl solutions by observing its optical absorption over a time span of 20 ms. In addition to experiments with NaCl solutions equilibrated with N2O at ambient pressure, a series of experiments are conducted with NaCl solutions equilibrated at 10 MPa hydrogen partial pressure and 0.1 MPa N2O partial pressure. In the presence of hydrogen, the Cl2− yield is significantly reduced compared to that in hydrogen free experiments. The effect of hydrogen on the radiolytic yield is more pronounced in 0.1 mol dm−3 NaCl solution than in the relatively concentrated NaCl solution. In parallel to the experiments the evolution of the Cl2− concentration is simulated using a kinetic model. Based on the comparison between measured and simulated optical absorption, which is mainly caused by the Cl2− radical, the rate constant of reaction Cl2−+Cl2−=Cl−+Cl3− is determined as 5.2(±0.8)×108 L mol−1 s−1 at zero ionic strength. This value is within the range of published rate constants for the Cl2− disproportionation reaction.