Bicarbonate ions enhanced surface Fe(II) regeneration and peroxymonosulfate activation on stainless-steel scrubber cathode for BPA degradation

Bicarbonate ions (HCO 3 − ), commonly present in natural water sources, exert complex influences on peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs). This study investigates the role of HCO 3 − in a novel electrochemical system using a stainless-steel scrubber cathode (SSSC) for PMS activation. The buffering effect of HCO 3 − shifts the dominant Fe(II) species from dissolved Fe 2+ ions to surface-bound Fe(II) (≡Fe(II)) within the HCO 3 − /PMS/SSSC system. Furthermore, HCO 3 − promotes ≡Fe(II)/≡Fe(III) redox cycling on the SSSC surface. These synergistic effects significantly enhance PMS activation, generating singlet oxygen ( 1 O 2 ) and Fe IV O as the primary oxidants responsible for BPA degradation. Identification of degradation intermediates elucidated two dominant pathways: hydroxylation and radical coupling. Toxicity assessment of these intermediates confirmed reduced environmental risks. The SSSC exhibited long-term stability and effective performance in real water matrices, demonstrating its practical applicability.