Degradation of sulfamethoxazole using UV and UV/H₂O₂ processes

Sulfamethoxazole (SMX) is a sulfonamide broad-spectrum antibiotic drug which is frequently detected in the aquatic environment. SMX is introduced into the environment mostly via municipal wastewater effluents as conventional treatment processes do not result in complete removal. As such, there is a need to investigate new treatment methods to improve the removal of SMX. The aim of this study was to investigate SMX degradation at pH 4.8 using UV- radiation and UV- radiation combined with H₂O₂ using a polychromatic (medium-pressure) mercury UV lamp. Primary characterization of the degradation products was performed using ¹H NMR spectroscopy and an analysis of the kinetics of degradation was performed. This study demonstrates that faster SMX degradation is achieved using a polychromatic UV light source compared to a 254 nm monochromatic light source, and that the addition of H₂O₂ enhances UV degradation when the mg L^-1 ratio of H₂O₂:SMX is less than 100. The calculated quantum yield was equal to 0.09 and the second-order rate constant for the degradation of SMX with hydroxyl radicals was 2.0×10⁹ M^-1s^-1.