Degradation of a stilbene dye (SOTGL) in aqueous solutions under gamma-radiation

The effect of radiation on the colour intensity of aerated, oxygen and nitrogen-saturated aqueous solution of Solophenyl Orange TGL has been investigated. Experiments show that the absorption band decreases gradually with the increase of the dose in all cases and the destruction of the skeleton of the dye molecule is promoted, by the presence of oxygen. The kinetics of degradation of solution of (SOTGL) turned out to be of the first order with respect to the low dye concentration (<0.14 g/l) and of zero order for dye concentration (>0.14 g/l). The radiochemical degradation yield (Gd) was calculated and was found to decrease experimentally with the increase of dose for low concentrations, whereas for higher concentrations such a behaviour can be presented by a straight line parallel to the dose axis. The influence of pH on the degradation of the dye was studied. The specific bimolecular rate constant of the reaction of SOTGL with the hydroxyl radical was determined by studying the effect of ethanol concentration on Gd using competition kinetics and was found to be 1.055·10⁹ M^–1 s^–1. Suggestions are made for possible low radiation dosimetry (about 1.5 kGy) by means of spectrophotometric analysis of the absorption spectra.