Degradation of the β-blocker propranolol by sulfite activation using FeS

A new advanced oxidation process, FeS-activated sulfite system, was firstly established to degrade β-blockers in water at near neutral pH. By choosing propranolol (PRO) as a model compound, the experimental conditions including FeS and sulfite doses, initial pH, dissolved oxygen, and co-existed components were investigated. Up to 95% of PRO was eliminated after 20 min reaction with FeS and sulfite doses being 20 mg/L and 1 mM, respectively, at initial pH 6.0. The PRO removal was pH-dependent with an optimal pH of 6.0, and the dissolved oxygen was essential. The presence of Cl − , HCO 3 − and humic acid could inhibit the FeS/sulfite process to different degrees. Radical scavenging experiment and electron spin resonance technology indicate that SO 4 − played a predominant role in PRO removal. The possible degradation pathway was subsequently inferred in terms of the detected products. The leached iron from FeS actually induced the activation of sulfite, rather than the structural Fe(II/III). Five other organic contaminants including metoprolol, fluoxetine, estriol, aniline, and p-chlorobenzoic acid could also be effectively degraded. In contrast with persulfate and peroxymonosulfate, the introducing of sulfite to FeS achieved much higher removal performance of PRO. Our study suggests a novel promising process of FeS/sulfite for water treatment.