1O2-dominated coral-like ZnO nanospheres modified Cu(OH)2@CF composite electrode for electro-fenton-degradation of tigecycline: In situ activation of H2O2 and non-radical degradation mechanism

In conventional Electro-Fenton systems, the oxidation process dominated by the Fe 2+ /Fe 3+ cycle and · OH radicals, although effective in degrading organic pollutants, is still limited by a narrow pH applicability range (2–4). To address this challenge, a coral-like ZnO nanospheres modified Cu(OH) 2 @CF composite electrode was synthesized in this study, which significantly broadened the applicable pH range (2–10). The ZnO/Cu(OH) 2 @CF composite electrode enhanced the selective generation of single-linear oxygen ( 1 O 2 ) and overcame the inherent defects, such as the extremely short lifetime of · OH (<1 μs), while enabling the efficient in situ generation of H 2 O 2 (272.51 mg/L, 30 min). And the complete degradation of tigecycline (TGC) was realized within 30 min with an operating cost of only 0.044 ¥·m −3 (energy consumption 0.076 kWh·m −3 ). and a low Tafel slope of only 24.80 mV·dec -1 is required for an efficient Electro-Fenton reaction. Notably, the ZnO/Cu(OH) 2 @CF composite electrode exhibited high degradation rates for a variety of typical antibiotics and could be adapted to different water quality conditions. After 10 cycles of use, its degradation rate of TGC was still as high as 92.67 %. The continuous flow reactor not only maintained more than 90 % degradation efficiency for TGC after 300 min of operation, but also maintained a high degradation rate of 80 % for mixed antibiotic wastewater. The dominant mechanism of action of 1 O 2 was deeply analyzed by bursting experiments and electron paramagnetic resonance (EPR). The two-dimensional correlation spectroscopy (2DCOS), three-dimensional fluorescence spectroscopy (3DEEMs) and liquid chromatography-mass spectrometry (LC-MS) techniques were used to reveal the degradation pathways of the pollutants and the toxicity evolution of the intermediates.