Radiation degradation of Congo Red in aqueous solution

Radiation-induced degradation of Congo Red (an azo dye) in aqueous solution was studied both with steady-state radiolysis and time-resolve techniques of pulse radiolysis and laser flash photolysis. Decomposition and mineralization of Congo Red by γ-rays was investigated with the changes of absorption spectra, degradation efficiency, TOC removal and pH changes of the solutions in different irradiation systems. The main radiolytic products resulting from steady-state radiolysis of Congo Red were examined by HPLC and LC–MS. Complete degradation of Congo Red was observed at different absorbed doses under diverse irradiation condition. The TOC removal of the solutions saturated with O2 or N2O reached 76% and 86% at the absorbed dose of 11.9 kGy, respectively. Pulse radiolysis and laser flash photolysis experiments were carried out to study the reaction of Congo Red with eaq- and OH. The reaction rate constants were determined.