Removal and degradation pathway study of sulfasalazine with Fenton-like reaction

The Fenton-like degradation of sulfasalazine solution is studied in this work. The effects of reaction parameters such as Fe3+ concentration, initial H2O2 dosage and the reaction temperature are evaluated. For sulfasalazine of 100 mg/L, the removal of sulfasalazine, chemical oxygen demand (COD) and total organic carbon (TOC) reached 99.5%, 84.2% and 41% in 60 min with 0.20 mM Fe3+ and 16 mM H2O2 at 35 degrees C, respectively. The complexed Fe3+ presents a reaction constant of 0.062 min(-1) mM(-1) while that of free Fe3+ is 2.526 min(-1) mM(-1) for sulfasalazine degradation. LC-MS technology was used to analysis the possible degradation intermediates. The degradation of sulfasalazine principally begins with the attack of hydroxyl radical on the azo-group as well as the sulfanilamido group. Both intramolecular rearrangement and bimolecular reaction occur simultaneously after the hydroxyl radical attack. Further attack of the active oxidative species results in the cleavage of the aromatic rings and the production of CO2. The degradation of industrial sulfasalazine wastewater with a COD of 3425 mg/L has also been achieved by Fenton reaction with different dosage of H2O2. Relatively better removal efficiency is observed at moderate Fe/H2O2 molar ratio from 1/5 to 2/5 for industrial sulfasalazine wastewater treatment. (C) 2011 Elsevier B.V. All rights reserved.