Singlet oxygen dominated peroxymonosulfate activation by CuO-CeO2 for organic pollutants degradation: Performance and mechanism

In this study, CuO-CeO2 was synthesized via an easy hydrothermal-calcination method and innovatively applied to peroxymonosulfate (PMS) activation for pollutants degradation under a non-radical oxidation pathway. Singlet oxygen (O-1(2)) was the dominated reactive oxygen species in the CuO-CeO2 /PMS system, leading to a dramatical degradation efficiency with Rhodamine B (RhB) as model compounds. The observed rate constant of the CuO-CeO2 /PMS system was 7-11 times higher than that of only PMS, CeO2/PMS and CuO/PMS systems. Also, under the reaction conditions of 1.6 mM PMS, 0.4 g/L catalyst and initial pH 7, the degradation efficiencies of RhB, Methylene Blue, Reactive Blue 19 and atrazine were respectively up to 100%, 85.39%, 72.84% and 98.44% in 60 min. X-ray photoelectron microscopy analysis indicated that the electrons transfer between CuO and CeO2 and the formation of oxygen vacancy in CeO2 should be responsible for the enhanced O-1(2) production, which involved a new non-radical oxidation pathway for PMS activation by CuO-CeO2 catalyst. Moreover, the combination of CuO and CeO2 increased reusability and stability of catalyst, allowing it remove more than 92% of RhB over a wide pH range (pH = 3-9). This study not only proved that CuO-CeO2 is an efficient and stable PMS activator but also provided a new insight into PMS activation through a non-radical oxidation pathway for organic contaminants removal from wastewater. (C) 2019 Elsevier Ltd. All rights reserved.