Degradation of Ibuprofen by the Electro/Fe3+/Peroxydisulfate Process: Reactive Kinetics, Degradation Products and Mechanism

Ibuprofen (IBU), a nonsteroidal anti-inflammatory drug, is one of the most widely used and frequently detected pharmaceuticals and personal care products in water bodies. This study examined the IBU degradation in aquatic solutions via ferric ion activated peroxydisulfate (PDS) coupled with electro-oxidation (EC/Fe3+/PDS). The degradation mechanisms involved three synergistic reactions in the EC/Fe3+/PDS system, including: (1) the electro-oxidation; (2) SO4•− generated from the activation of PDS by ferrous ions formed via cathodic reduction; (3) SO4•− generated from the electron transfer reaction. The radical scavenging experiments indicated that SO4•− and •OH dominated the oxidation process. The effects of the applied current density, PDS concentration, Fe3+ dosage, initial IBU concentration and initial pH as well as inorganic anions and humic acid on the degradation efficiency, were studied, and the degradation process of IBU followed the pseudo-first-order kinetic model. About 99.37% of IBU was removed in 60 min ((Fe3+ concentration) = 2.0 mM, (PDS concentration) = 12 mM, (initial IBU concentration) = 30 mg/L, current density = 15 mA/cm2, initial pH = 3). Finally, seven intermediate compounds were identified and probable IBU degradation pathways in the EC/Fe3+/PDS system were speculated.