Self-assembled cobalt disulfide-graphene oxide composite for efficient and environmentally friendly removal of antibiotic ornidazole through PMS activation

Abstract

In this study, a highly active peroxymonosulfate (PMS) activator was prepared by the self-assembly of cobalt disulphide (CoS2) nanoparticles on the surface of graphene oxide nanosheets using a simple electrostatic self-assembly method. The catalysts were characterized, and their ability to activate PMS to eliminate ornidazole (ORZ) was assessed. Degradation experiments showed that the CoS2−GO/PMS system exhibited excellent ORZ degradation performance, removing 99.7 % of ORZ in 10 min. In four consecutive cycles, the reduction rate of ORZ removal by the composite catalyst decreased by only 1.8 %. Both radical quenching experiments and electron paramagnetic resonance (EPR) tests revealed that sulfate radical (SO4•-) and superoxide radical (O2•-) contributed to the major reactive oxygen species (ROS). X-ray photoelectron spectroscopy (XPS) results showed that the sulfur (S) species in CoS2 played an important role in the Co(III)/Co(II) cycle, driving the catalyst to exhibit excellent PMS activation. Liquid chromatography-mass spectrometry (LC-MS) was used to determine the possible decomposition processes and identify the intermediates of the ORZ medium. Remarkably, the biotoxicity assessment of degraded intermediates analyzed by ECOSAR software indicated the environmentally friendly features of the degradation process.