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

Urchin-like Co3O4 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 Co3O4-rGO were characterized. Compared with Co3O4, Co3O4-rGO possessed excellent activity in peroxymonosulfate (PMS) activation for ibuprofen (IBU) degradation. Then, the influences of Co3O4-rGO dosage, IBU concentration, PMS concentration and pH on IBU and TOC removal were investigated, respectively. Furthermore, both ·OH and SO4•- were identified to be the main active species, and SO4•- made the predominant contribution. In addition, residual PMS and SO4•- quantification demonstrated that Co3O4-rGO could activate PMS more effectively, and produce more SO4•-. The mechanistic study revealed that the valence state conversion of Co2+/Co3+ was the critical PMS activation mechanism. Moreover, the enhanced activity of Co3O4-rGO is accounted for the combination of multiple unique characteristics, including excellent electronic transmission (Co2+ to Co3+, Co2+ to PMS), more active sites, and chemical bonds between Co3O4 and rGO. 13 degradation products were determined and possible degradation routes were proposed based on the results of LC-MS/MS. Finally, the Co3O4-rGO/PMS system also exhibited satisfactory removal of IBU in real water matrices.