Kinetic and mechanistic study of sulfadimidine photodegradation under simulated sunlight irradiation

Abstract

Background: The extensive uses of sulfadimidine (SDMD) resulted in its presence in water bodies, and subsequent posed risks to eco-environment and human health. In this study, photodegradation of SDMD in water was studied under UV–Visible irradiation. The intermediates, degradation pathways of SDMD photodegradation and ecological risk of SDMD were investigated as well. Results: SDMD was rapidly degraded under alkaline conditions. Nitrate ion enhanced SDMD degradation under UV–Vis irradiation, while dissolved organic matter and Fe(III) inhibited its decay, and bicarbonate ion did not exert any effect. The reactive species involved in the SDMD photodegradation was singlet oxygen. Four major transformation products were identified by high-performance liquid chromatography–mass spectrometry (HPLC–MS), and the photolytic pathway was also proposed. Photoinduced hydrolysis, desulfonation and photooxidation were the major photodegradation mechanisms for SDMD. Toxicity analysis with Vibrio fischeri showed an obvious decrease in toxicity of the reaction solution, from the initial inhibition rate of 38.5% to 0% after 150-min irradiation. Conclusion: Initial pH and common water constituents influence the photo-degradation of SDMD under UV–Vis irradiation. Photodegradation of SDMD could reduce its ecological risk in the aqueous solution.