Removal of 17β-estrodial in a bio-electro-Fenton system: contribution of oxidation and generation of hydroxyl radicals with the Fenton reaction and carbon felt cathode

Abstract

A bio-electro-Fenton (BEF) system equipped with a Fe@Fe₂O₃/non-catalyzed carbon felt (NCF) cathode was optimized, and the generation of hydroxyl radicals was confirmed for E2 removal. External resistance was the most significant factor influencing E2 removal. When the external resistance was close to the internal one, both the Fe@Fe₂O₃/NCF and NCF systems removed over 90% of E2. Sorption experiments suggested that oxidation played a major role in E2 removal instead of cathode sorption. Up to 0.54 mmol L⁻¹ of hydroxyl radicals were detected in the Fe@Fe₂O₃/NCF system, mostly produced via the Fenton reaction. While in the NCF system, hydroxyl radicals were also detectable at around 0.059 mmol L⁻¹, possibly produced through the activation of H₂O₂ by persistent free radicals contained in the combustion-generated carbon felt. Although the BEF system was confirmed to possess a much stronger oxidation capacity, a microbial fuel cell equipped with NCF is already efficient in removing trace amounts of organic pollutants.