Non-radical transformation of oxytetracycline by Vo-MnO@C/Pt0.8Au0.2-anode-activated peroxymonosulfate: Influencing factors, mechanism, and toxicity assessment

Abstract

Non-radical oxidation processes based on electrochemically activating peroxymonosulfate (PMS) have attracted considerable attention owing to their mild oxidative properties and selective degradation of organic pollutants. In this study, a Vo-MnO@C/Pt0.8Au0.2 modified anode is prepared to activate PMS and generate non-radical oxidation that produces singlet oxygen (1O2) for oxytetracycline (OTC) degradation. Here, the PMS is not only an oxidant but also the only supporting electrolyte, which can effectively reduce the influx of additional ions. Efficient OTC degradation is achieved in a wide pH range (pH = 3–9) and is not inhibited in natural water samples, even in the case of the seawater sample (100 % removal in 60 min). About 96.8 % of OTC at a concentration of 10 mg/L could be degraded with 10 mA cm−2, pH = 9.0, and 1.0 mM PMS in 60 min. Furthermore, the Vo-MnO@C/Pt0.8Au0.2/EPMS system can efficiently degrade various antibiotics. In particular, the 1O2 plays a critical role in OTC degradation. Electro-catalysis and oxygen vacancies (Vo) contribute to the activation of PMS along a non-radical pathway, which is further confirmed through quenching experiments and electron paramagnetic resonance (EPR) tests. In addition, the Toxicity Estimation Software Tool (T.E.S.T) and flow cytometry tests indicate that the Vo-MnO@C/Pt0.8Au0.2/EPMS system reduces the toxicity of OTC-contaminated water. Owing to its reusability with a degradation efficiency of about 90 % after four cycles, the Vo-MnO@C/Pt0.8Au0.2/EPMS system has good prospects for practical application. In summary, our work highlights the potential of a non-radical oxidation process for decontaminating pharmaceutical and personal care products (PPCPs) in complex water matrices.