Improvement of the three-dimensional electrochemical degradation of amoxicillin using Co₃O₄/GAC as both particle electrode and catalyst for peroxymonosulfate activation

In this study, a novel three-dimensional (3D) electrode system (3D-Co₃O₄/GAC-PMS) was constructed that can effectively degrade amoxicillin (AMX) in aqueous solution using granular activated carbon (GAC) loaded with Co₃O₄ catalyst (Co₃O₄/GAC) as a catalyst for the activation of peroxymonosulfate (PMS) as well as particle electrode. The effects of the main operating parameters on AMX degradation, TOC removal, electrical energy consumption and current efficiency were investigated. Under the optimum operating conditions (initial solution pH of 5.9, PMS concentration of 13 mmol/L, current density of 5.6 mA/cm²), 99.9% of AMX was degraded after 10 min of treatment and 96.8% of TOC was removed after 120 min of treatment. Meanwhile, the electrical energy consumption of the system was very small, only 45.1 kWh/kg TOC. Comparative experiments with other systems and kinetic analysis have confirmed the superior performance of the 3D-Co₃O₄/GAC-PMS system for the degradation of AMX. During five cycles, the Co₃O₄/GAC particle electrode showed excellent stability and long lifetime. The 3D-Co₃O₄/GAC-PMS system simultaneously degraded 100% of three different pharmaceuticals (amoxicillin, ciprofloxacin and acetaminophen) after 8 min of reaction and removed 88.1% TOC after 120 min of reaction, which suggested the applicability of the system for real wastewater treatment. The degradation of AMX was confirmed using UV–Vis spectroscopy and the reaction mechanism of the 3D-Co₃O₄/GAC-PMS system was proposed. Based on the intermediates detected by ultra-high pressure liquid chromatograph coupled with quadrupole time-of-flight mass-spectrometry, the degradation pathways of AMX in the 3D-Co₃O₄/GAC-PMS system were presented.