Urchin-like Co3O4 anchored on reduced graphene oxide with enhanced performance for peroxymonosulfate activation in ibuprofen degradation.

Urchin-like CoO anchored on reduced graphene oxide was easily prepared with hydrothermal reaction by using a cheap and green agent. First, the surface morphology and physicochemical properties of CoO-rGO were characterized. Compared with CoO, CoO-rGO possessed excellent activity in peroxymonosulfate (PMS) activation for ibuprofen (IBU) degradation. Then, the influences of CoO-rGO dosage, IBU concentration, PMS concentration and pH on IBU and TOC removal were investigated, respectively. Furthermore, both ·OH and SO were identified to be the main active species, and SO made the predominant contribution. In addition, residual PMS and SO quantification demonstrated that CoO-rGO could activate PMS more effectively, and produce more SO. The mechanistic study revealed that the valence state conversion of Co/Co was the critical PMS activation mechanism. Moreover, the enhanced activity of CoO-rGO is accounted for the combination of multiple unique characteristics, including excellent electronic transmission (Co to Co, Co to PMS), more active sites, and chemical bonds between CoO and rGO. 13 degradation products were determined and possible degradation routes were proposed based on the results of LC-MS/MS. Finally, the CoO-rGO/PMS system also exhibited satisfactory removal of IBU in real water matrices.