Stoichiometric hydrogen peroxide versus hypochlorite generation via dual-cell continuous flow system enables singlet oxygen-dominated phenol oxidation

ABSTRACT A dual-cell continuous-flow system that decouples the production of H2O2 and ClO- to to produce 1O2 for efficient degradation of phenol and other organic contaminants. Current electrochemical processes utilizing singlet oxygen (1O2) for wastewater treatment face limitations due to inefficient hydrogen peroxide (H2O2) generation and uncontrollable stoichiometric ratios between H2O2 and hypochlorite (ClO−). To address these operational bottlenecks, this study developed a dual-cell continuous-flow system that decouples the production of H2O2 and ClO− to degrade phenol and other organic contaminants. The system features a natural air diffusion cathode (ADC) for energy-efficient H2O2 generation without aeration and a dimensionally stable anode (DSA) for active chlorine production. By optimizing the applied current ratio (ADC:DSA = 2:1), an optimal 1:1 H2O2/ClO− stoichiometric molar ratio was achieved. This precise control successfully maximized 1O2 production (steady-state concentration: 5.77 ± 0.24 × 10−10 mM), resulting in a 97.9% removal of phenol under optimal conditions. Additionally, the system achieved removal rates of 71.6% for bisphenol A and 81.3% for sulfamethoxazole. Furthermore, the 1O2-dominated oxidation pathway suppressed the formation of chlorinated byproducts by 24–48% compared to a conventional single-cell electrochemical method. Overall, this engineered dual-cell architecture effectively overcomes the intrinsic bottlenecks of conventional electro-oxidation, establishing a robust, 1O2-driven paradigm for the safe and selective pretreatment of refractory wastewaters.