Insight into synergetic mechanism of CuyMn5-yOx/hG-activated peroxydisulfate enhances tetracycline antibiotics degradation and toxicity assessment

Abstract

Tetracycline is a typical ecologically toxic antibiotic that easily causes environmental contamination. An attractive approach toward pollution control is the implementation of sulfate radical-based advanced oxidation processes (SO4·--AOPs), and in that regard, it is critical to generate and stabilize highly-oxidative species over an excellent catalytic system to degrade tetracycline antibiotics. In this work, we investigated a strategy for employing a synergetic role of CuOx to enlarge the MnsbnO covalency and tailor defect sites, which could enhance the intrinsic activity of CuyMn5-yOx/hG catalysts for boosted peroxydisulfate (PDS) activation and tetracycline degradation via radical and nonradical processes. Comprehensive characterization revealed that MnO bonds weakened, while the CuyMn5-yOx redox cycling provided the main active center for PDS activation by radical processes. Moreover, abundant defect sites of the carbon-based co-catalyst promoted the adsorption of PDS and tetracycline and, thus, their catalysis via nonradical processes. Structural characterization indicated that Cu2.5Mn2.5Ox/hG catalysts prepared using the solid-phase method significantly increased the ratio of defects sites and enlarged the MnsbnO covalency, enhancing PDS activation. Particularly, OH· and SO4·- radicals were critical reactive oxygen species, Mn(Cu) sbnO bond weakening, and defects are the key activation sites. Furthermore, degradation pathways, the toxicity of intermediate species, and the reaction mechanisms of the tetracycline degradation catalyzed by CuyMn5-yOx/hG were determined. Removing CONH2 functional groups and the C2-C3 structural sites ring-opening played a vital role in tetracycline degradation. The Cu2.5Mn2.5Ox/hG catalyst was demonstrated to be effective in tetracycline degradation with a low environmental impact, and our findings provide valuable novel insights for further development of efficient SO4·--AOPs catalysts.