Degradation of an imidazolium-based ionic liquid in water using monopersulfate catalyzed by Dahlia flower-like cobalt oxide

As the imidazolium-based ionic liquid (IL), 1-Butyl-3-methylimidazolium chloride (BMIMCl), is increasingly employed in various applications, release of BMIM cation into the environment has posed serious threats on aquatic ecology. Thus, it is imperative to eliminate BMIM from water, and, among various techniques for eliminating BMIM, chemical oxidation is the most effective technique. Nevertheless, studies of using SO4−-based chemical oxidation methods for degrading BMIM are still very limited; thus this study aims to develop an effective SO4−-based chemical oxidation process for degrading BMIM. As monopersulfate (MPS) is employed as a source of SO4−, a special cobalt (Co)-based catalyst is proposed and developed here by fabricating Co3O4 into a unique Dahlia flower-like morphology. Such a Dahlia flower-like Co3O4 (DFCoO) not only can exhibit the flower configuration, but also its floral petal components can consist of many filament-like Co3O4 nanostructures, making this DFCoO possess several advantageous properties over the conventional Co3O4 nanoparticle (NP), including higher redox activity, more reactive surface, higher surface area and larger pore volume. Thus, DFCoO shows a much higher catalytic activity than Co3O4 NP to activate MPS for degrading BMIM. A higher MPS dosage and reaction temperature also enhance BMIM degradation by DFCoO + MPS. DFCoO is reusable for activating MPS to degrade BMIM over multiple cycles. BMIM degradation mechanism and pathway by this DFCoO + MPS is also elucidated by identifying radical species and degradation intermediates. The findings of this study offer an useful approach for developing an advantageous catalyst for sulfate-based degradation of BMIMCl.