Synergistic degradation of antibiotic sulfadiazine in a heterogeneous ultrasound-enhanced Fe0/persulfate Fenton-like system

In this study, a novel ultrasound-enhanced heterogeneous Fe-0/persulfate (US/Fe-0/PS) system was developed and investigated for the degradation of an antibiotic sulfadiazine (SD). It was demonstrated that the US/Fe-0/PS system could achieve a significant synergy in the degradation efficiency of SD, as compared to its corresponding comparative systems. The SD degradation in the US/Fe-0/PS system could be applied by the pseudo-first-order kinetic with a k(obs) (SD) value of 3.4 +/- 0.20 h(-1). Affecting factors such as initial pH, dosage ratio of [Fe-0]:[PS], US input power and reaction temperature were further studied. SD could be effectively degraded with a relatively low PS dosage at a broad pH range of 3-7. Simultaneous evolution of soluble iron species and PS was evaluated in three comparative systems (US/Fe-0, Fe-0/PS and US/Fe-0/PS) during the reaction. It could be concluded that the promotional role of US would be dual in the US/Fe-0/PS system, i.e. enhancement in the heterogeneous iron corrosion reactions and acceleration in the bulk radical reactions. Identification of the degradation intermediates indicated that sulfate radical (SO4-) oxidation was the main SD degradation pathway. Attacking of the amine group in the benzene ring would be its first step, followed by cleavage of C-N bonds in the heterocyclic ring. Another degradation pathway, i.e. direct cleavage of the S-N bond should be also present. (C) 2014 Elsevier B.V. All rights reserved.