Activation of peracetic acid by electrodes using biogenic electrons: A novel energy- and catalyst-free process to eliminate pharmaceuticals

Peracetic acid (PAA) has received increasing attention as an alternative oxidant for wastewater treatment. However, existing processes for PAA activation to generate reactive species typically require external energy input (e.g., electrically and UV-mediated activation) or catalysts (e.g., Co2+), inevitably increasing treatment costs or introducing potential new contaminants that necessitate additional removal. In this work, we developed a catalyst-free, self-sustaining bioelectrochemical approach within a two-chamber bioelectrochemical system (BES), where a cathode electrode in-situ activates PAA using renewable biogenic electrons generated by anodic exoelectrogens (e.g., Geobacter) degrading biodegradable organic matter (e.g., acetic acid) in wastewater at the anode. This innovative BES-PAA technique achieved 98 % and 81 % removal of 2 mu M sulfamethoxazole (SMX) in two hours at pH 2 (cation exchange membrane) and pH 6 (bipolar membrane) using 100 mu M PAA without external voltage. Mechanistic studies, including radical quenching, molecular probe validation, electron spin resonance (ESR) experiments, and density functional theory (DFT) calculations, revealed that SMX degradation was driven by reactive species generated via biogenic electron-mediated O-O cleavage of PAA, with CH3C(O) OO center dot contributing 68.1 %, center dot OH of 18.4 %, and CH3C(O)O center dot of 9.4 %, where initial formation of center dot OH and CH3C(O) O center dot rapidly reacts with PAA to produce CH3C(O)OO center dot. The presence of common water constituents such as anions (e.g., Cl-, NO3-, and H2PO4- ) and humic acid (HA) significantly hinders SMX removal via the BES-PAA technique, whereas CO32- and HCO3- ions have a comparatively minor impact. Additionally, the study investigated the removal of various pharmaceuticals present in secondary treated municipal wastewater, attributing differences in removal efficiency to the selective action of CH3C(O)OO center dot. This research demonstrates a novel PAA activation method that is ecologically benign, inexpensive, and capable of overcoming catalyst deactivation and secondary pollution issues.