Polarized heterogeneous CuO-CN for peroxymonosulfate nonradical activation: An enhancement mechanism of mediated electron transfer

Abstract

• The extreme positive potential of CuO-CN enhanced nonradical PMS reactions. • The enhanced mechanism was elucidated by density functional theory (DFT). • Electron transfer dominated in this nonradical pathway. • Stable removal contaminant in continuous flow fixed bed reactor in actual water body. The combination of peroxymonosulfate (PMS) and catalyst to form a surface-bound reaction complex is a key step in the electron transfer pathway, which needs to be further explored for enhancing the rate of non-radical reactions. Based on experiments and density functional theory (DFT) calculations, a non-radical reaction enhancement mechanism is proposed, that is, the introduction of g-C 3 N 4 (CN) into the CuO-CN heterogeneous charge imbalance distribution, thereby enhancing the outer surface electron-poor CuO. Therefore, it is easy to couple negatively charged PMS to enhance non-radical activation, and resulting in 29 times increase in the degradation rate of the drug. The electron transfer mechanism of interaction between PMS, CuO and the organic contaminant was proposed as the dominant reactive pathway. Benefiting from an electron transfer mechanism at the CuO site, the PMS/CuO-CN system exhibited satisfactory removal of diclofenac sodium (DCF) in a wide pH range (3–11), in the presence of inorganic anions and in real water matrix (tap water, surface water and ground water). In a continuous-flow reaction with a fixed bed reactor, over 90% of DCF could be stably removed. This work could deepen the understanding of the key role of the enhancement mechanism of the non-radical reaction of CuO and provide a reference for the practical application of non-free radical advanced oxidation technology.