Highly dispersed copper single-atom catalysts activated peroxymonosulfate for oxytetracycline removal from water: Mechanism and degradation pathway

In this work, copper single-atom catalysts (Cu-SACs) were synthesized by a simple one-step calcination method for the degradation of oxytetracycline (OTC). Based on XRD, SEM, EDX, HAADF-STEM, XANES and EXAFS analyses, it was demonstrated that highly dispersed Cu-SACs were successfully prepared. The influence of different factors (i.e. amount of peroxymonosulfate and catalyst and initial pH) on the degradation performance was systematically investigated in order to obtain optimal experimental conditions. Under the suitable conditions, the degradation efficiency of OTC could reach 96.47 % within 60 min. In addition, in the presence of high concentrations of Cl-, the production of Cl2 as well as HOCl promotes the degradation of OTC. CO32– and HCO3–, which generate selective CO3•- in the early stages of degradation, also accelerate the degradation of OTC. The experimental results of free radical quenching and the detection of free radicals by electron paramagnetic resonance (EPR) demonstrated that the •OH and 1O2 played a major role in the degradation process. Liquid chromatography-mass spectrometry (LC-MS) analysis of some intermediates and possible degradation pathways in the degradation of OTC. The applicability of the system was verified for different practical water samples, where the degradation efficiency of OTC in hospital wastewater could reach 88.07 %. The experimental results showed that Cu-SACs has outstanding performance in degrading OTC.