Efficient degradation of sulfamethazine in water by the novel VUV/UV/persulfate process

Abstract

Antibiotic residues in water present significant ecological and public health challenges, necessitating the development of efficient advanced oxidation processes. The present study investigated a novel vacuum ultraviolet/ultraviolet/persulfate (VUV/UV/PS) process for degrading sulfamethazine (SMN), a representative sulfonamide antibiotic, in water. SMN degradation was assessed under UV, UV/PS, VUV/UV, and VUV/UV/PS conditions. All processes exhibited pseudo-first-order kinetics, with apparent rate constants of 0.12, 0.28, 0.25, and 0.52 min^‒1, respectively. The VUV/UV/PS process achieved near-complete SMN removal (99.4%) within 10 min, surpassing the performance of UV/PS (94.4%) and VUV/UV (91.7%). Quenching by tert-butanol and methanol decreased the apparent rate constant to 0.31 and 0.16 min^‒1, respectively, indicating the contributions of both hydroxyl radicals and sulfate radicals. The degradation rate increased with persulfate concentration but approached saturation above 5 mM. Higher initial SMN concentrations inhibited the reaction kinetics, while mildly acidic conditions enhanced degradation. Chloride and sulfate had minimal effects, whereas nitrate, bicarbonate, and particularly natural organic matter significantly inhibited degradation. Analysis of transformation products indicated three concurrent pathways: N–S bond cleavage, hydroxylation, and oxidation, followed by further oxidation of intermediates. These findings demonstrate the VUV/UV/PS process as a rapid and mechanistically robust approach for SMN removal in water treatment.

KEY WORDS: Sulfamethazine, Degradation, Vacuum ultraviolet, Persulfate, Radicals

Bull. Chem. Soc. Ethiop. 2026, 40(11), 2347-2359                                                      

DOI:   https://dx.doi.org/10.4314/bcse.v40i11.5