Reaction of antibiotic sulfadiazine with manganese dioxide in aqueous phase: Kinetics, pathways and toxicity assessment.

Sulfonamide antibiotics are often detected in terrestrial and aquatic environment, but little is known about abiotic degradation of these antibiotics. In the present study, the degradation of the sulfonamide antibiotic sulfadiazine by a synthesized δ-MnO was investigated. The initial reaction rate of sulfadiazine oxidized by manganese dioxide increased as the solution pH decreased by weakening electrostatic attraction between sulfadiazine and MnO and enhancing the reduction potential of MnO. The presence of metal ions (Mn, Na and Ca), especially Mn, decreased the initial reaction rate by competitively adsorbing and reacting with MnO. Two different products were identified during the reaction of sulfadiazine with MnO and the transformation of parent compound started with the formation of sulfadiazine radicals. Furthermore, toxicity assay results showed that the toxicity of products produced by bacteria decreased with elapse of reaction time. Results from the present study indicate that manganese dioxides in environmental matrix could be helpful in dissipation of sulfadiazine released into the environment.