A simple Fe(3+)/bisulfite system for rapid degradation of sulfamethoxazole

Sulfate radical (SO(4)˙(−)) based oxidation technologies have been widely used in the remediation of antibiotic-containing wastewater. Activated persulfates are efficient reagents for achieving SO(4)˙(−), but the storage and transportation of concentrated persulfates present associated safety issues. In this study, bisulfite (BS) was used as an alternative precursor for replacing persulfates, and a simple advanced oxidation system (Fe(3+)/BS) for generating SO(4)˙(−) and hydroxyl radical (HO˙) was formulated and evaluated for removing sulfamethoxazole (SMX) from contaminated water. The initial pH, dosages of Fe(3+) and BS, as well as the water matrix were investigated to improve the SMX degradation. The results indicated that 1 μmol L(−1) SMX was completely removed within 5 min at optimum initial pH of 4.0, Fe(3+) dosage of 10 μmol L(−1), BS dosage of 100 μmol L(−1) and temperature of 25 °C. The presence of HCO(3)(−) and natural organic matter (NOM) showed obviously negative effects on SMX degradation, while Cu(2+) could slightly promote the degradation of SMX if its concentration was in an appropriate range (∼1 μmol L(−1)). Scavenger quenching experiments confirmed the presence of SO(4)˙(−) and HO˙, which resulted in efficient SMX degradation in the Fe(3+)/BS system. During the radical chain reactions, Fe(2+) and Fe(3+) could be converted into each other to form self-circulation in this system. The degradation pathway of SMX by Fe(3+)/BS was proposed including hydroxylation and bond cleavage.