Efficient electrochemical oxidation of antibiotic wastewater using a graphene-loaded PbO₂ membrane anode: Mechanisms...

This paper aims to develop a flow-through electrochemical system with a series of graphene nanoparticles loaded PbO₂ reactive electrochemical membrane electrodes (GNPs-PbO₂ REMs) on porous Ti substrates with pore sizes of 100, 150, 300 and 600 μm, and apply them to treat antibiotic wastewater. Among them, the GNPs-PbO₂ with Ti substrate of 150 μm (Ti-150/GNPs-PbO₂) had superior electrochemical degradation performance over the REMs with other pore sizes due to its smaller crystal size, larger electrochemical active specific area, lower charge-transfer impedance and larger oxygen evolution potential. Under the relatively optimized conditions of initial pH of 5, current density of 15 mA cm^-2, and membrane flux of 4.20 m³ (m²·h)^-1, the Ti-150/GNPs-PbO₂ REM realized 99.34% of benzylpenicillin sodium (PNG) removal with an EE/O of 6.52 kWh m^-3. Its excellent performance could be explained as the increased mass transfer. Then three plausible PNG degradation pathways in the flow-through electrochemical system were proposed, and great stability and safety of Ti-150/GNPs-PbO₂ REM were demonstrated. Moreover, a single-pass Ti-150/GNPs-PbO₂ REM system with five-modules in series was designed, which could consistently treat real antibiotic wastewater in compliance with disposal requirements of China. Thus, this study evidenced that the flow-through electrochemical system with the Ti-150/GNPs-PbO₂ REM is an efficient alternative for treating antibiotic wastewater.