Practical-scale on-site H₂O₂ production with a divided continuous-flow electrochemical reactor: performance...

Electrochemical on-site H₂O₂ production via two-electron oxygen reduction is a promising alternative for decentralized water treatment, yet practical-scale application remains challenging due to scale-up difficulties and mismatches between reactor design and operational requirements. This study systematically investigates a divided continuous-flow electrochemical reactor for practical-scale on-site H₂O₂ production. The scaled-up divided reactor, featuring a gas diffusion electrode (effective area: 187.5 cm²) operated in single-pass mode, outperformed the undivided counterpart. Under optimal conditions (current density of 30 mA/cm², air flow rate of 0.6 L/min, Na₂SO₄ concentration of 0.05 M, and electrolyte flow rate of 30 mL/min), the system achieved an H₂O₂ production of 1678.15 mg/L, with a current efficiency of 86.04% and an energy consumption of 9.41 kWh/kg. Water constituent tests revealed that H₂O₂ production was significantly inhibited by metallic cations (e.g., Fe³⁺, Ni²⁺, Mg²⁺) and certain anions (e.g., HCO₃^-), whereas organic matters (e.g., humic acid, phenol) showed negligible effects. Using tap water as the electrolyte matrix, the system maintained stable H₂O₂ production for over 100 h with CE above 76%. The total operating cost (based on 100 wt% H₂O₂) was estimated at 9.35 ¥/kg, with electricity accounting for approximately 69%. A continuous-flow treatment system integrating a UV reactor achieved 85.5% COD removal from real secondary wastewater, and the treatment cost was estimated at 5.91 ¥/m³. This study demonstrates the applicability of electrochemical on-site H₂O₂ production as an economical and environmentally friendly alternative for real-world water treatment applications.