Sulfadiazine degradation by combination of hydrodynamic cavitation and Fenton–persulfate: parametric optimization and deduction of chemical mechanism.

This paper reports the degradation of the sulfadiazine (SDZ) drug with a hybrid advanced oxidation process (AOP) of heterogeneous α-Fe₂O₃/persulfate coupled with hydrodynamic cavitation. The major objectives of the study are parametric optimization of the process and elucidation of the chemical mechanism of degradation. The optimum conditions for maximum SDZ degradation of 93.07 ± 1.67% were as follows: initial SDZ concentration = 20 ppm, pH = 4, α-Fe₂O₃ = 181.82 mg/L, Na₂S₂O₈ = 348.49 mg/L, H₂O₂ = 0.95 mL/L, inlet pressure = 0.81 MPa (8 atm), orifice plate configuration: hole dia. = 2 mm and number of holes = 4. Density functional theory (DFT) calculations revealed that the atoms of SDZ with a high Fukui index (f⁰) were potentially active sites for the attack of ^•OH and SO 4 · - radicals. Fukui index calculation revealed that atom 11 N has a higher value of f⁰ (0.1026) for oxidation at the α-amine group of the sulfadiazine molecule. Degradation intermediates detected through LC–MS/MS analysis corroborated the results of DFT simulations. Using these results, a chemical pathway has been proposed for SDZ degradation. [ABSTRACT FROM AUTHOR]