Oxidative degradation of sulfathiazole by Fenton and photo-Fenton reactions

VELÁSQUEZ, M.; SANTANDER, O.; CONTRERAS, D.; YÁÑEZ, J.; ZAROR. C.; SALAZAR, R.; PÉREZ, M.; MANSILLA, H.:
Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances and Environmental Engineering, 49:6 (2014) 661-670.

DOI: 10.1080/10934529.2014.865447

Abstract

This article presents experimental results on 47 µmol L^-1 sulfathiazole (STZ) degradation by Fenton and photo-Fenton reactions using multivariate analysis. The optimal experimental conditions for reactions were obtained by Response Surface Methodology (RSM). In the case of the Fenton reactions there were 192 µmol L^-1 ferrous ions (Fe(II)) and 1856 µmol L^-1 hydrogen peroxide (H₂O₂), as compared with 157 µmol L^-1 (Fe(II)) and 1219 µmol L^-1 (H₂O₂) for photo-Fenton reactions. Under these conditions, around 90% of STZ degradation were achieved after 8 minutes treatment by Fenton and photo-Fenton reactions, respectively. Moreover, a marked difference was observed in the total organic carbon (TOC) removal after 60-min treatment, achieving 30% and 75% for the Fenton and photo-Fenton reactions, respectively. Acetic, maleic, succinic and oxamic acids could be identified as main Fenton oxidation intermediates. A similar pattern was found in the case of photo-Fenton reaction, including the presence of oxalic acid and ammonia at short periods of irradiation with UV-A. The calculated values of Average Oxidation State (AOS) corroborate the formation of oxidized products from the initial steps of the reaction.