(2021) Separation and Purification Technology_Degradation of an imidazolium-based ionic liquid in water using monopersulfate catalyzed by Dahlia flower-like cobalt oxide

Hsiao C.-Y., Wang H., Kwon E., Thanh B.X., You S., Hu C., Lin K.-Y.A.

(Elsevier B.V.) Separation and Purification Technology ISSN: 13835866 Vol.274 Issue. Article No.118668 DOI: 10.1016/j.seppur.2021.118668

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^[rad]−-based chemical oxidation methods for degrading BMIM are still very limited; thus this study aims to develop an effective SO₄^[rad]−-based chemical oxidation process for degrading BMIM. As monopersulfate (MPS) is employed as a source of SO₄^[rad]−, 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. © 2021

This work is supported by the Ministry of Science and Technology (MOST)(110-2636-E-005-003-), Taiwan, and financially supported by the “Innovation and Development Center of Sustainable Agriculture” from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE), Taiwan. The authors gratefully acknowledge the use of SQUID000200 of MOST110-2731-M-006-001 belonging to the Core Facility Center of National Cheng Kung University.