Gamma radiolytic degradation of 3,4-dichloroaniline in aqueous solution

• Aqueous 3,4-DCA could be degraded by gamma-ray irradiation effectively.
• Role of eaq- during the degradation process was analyzed.
• Sequence of free radicals’ contribution to 3,4-DCA degradation was OH > eaq- > H.
• Quantum efficiency ratio of OH, eaq- and H for the degradation of 3,4-DCA was 1:1:4.
• Degradation mechanism of aqueous 3,4-DCA by gamma-ray irradiation was proposed.

Degradation of aqueous 3,4-dichloroaniline (3,4-DCA) using gamma-ray irradiation was attempted in this study. The role of eaq- during the degradation process was analyzed in detail. The results demonstrated that effective degradation of aqueous 3,4-DCA using gamma-ray irradiation was realized; when the initial concentration of 3,4-DCA was 0.050 mmol L−1, and the irradiation dose was 0.4 kGy, the degradation efficiency of 3,4-DCA reached 96.2%. The degradation process of 3,4-DCA could be depicted by the pseudo first order reaction kinetics. Dechlorination was observed during the degradation process, and the concentration of detected Cl− in the treated 3,4-DCA solution increased with increasing irradiation dose. The sequence of the contribution of free radicals to the 3,4-DCA degradation was OH > eaq- > H. The quantum efficiency ratio of OH, eaq- and H for the degradation of 3,4-DCA was 1:1:4. The degradation efficiency of 3,4-DCA was accelerated by the addition of H2O2, and the appropriate addition amount was 0.05% (v/v). However, HCO3−, NO3− and NO2− (as additives) reduced the degradation efficiency of 3,4-DCA. A gas chromatograph–mass spectrometer was employed to identify the degradation intermediates, indicating that p-chloroaniline was the primary degradation intermediate with the addition of 2-propanol.