Hierarchical porous nanosheets of Co-Mn bimetallic oxide from deep eutectic solvent for highly efficient peroxymonosulfate activation

The development of highly active catalysts is the key to the successful application of sulfate radical (SO 4 ·− )-based advanced oxidation processes (AOPs) to wastewater treatment. Herein, bimetallic oxide CoMn2O4 hierarchical porous nanosheets (CoMn2O4 HPNSs) were constructed using glucose/urea deep eutectic solvent (DES) as sustainable solvent and self-formed sacrificial carbon templates. The prepared CoMn2O4 HPNS exhibited outstanding peroxymonosulfate (PMS) activation performance, achieving the rapid degradation of refractory organic compounds in wastewater, including 5-sulfosalicylic acid (100%), acetaminophen (100%), oxtetracycline (100%), and sulfamethoxazole (91%) within 20 min. This excellent performance was attributed not only to the synergistic catalytic effect of Co-Mn bimetals, but also to the hierarchical porous structure which exposes more active sites and accelerates the migration of PMS and organic pollutants. In addition, CoMn2O4 HPNS also showed excellent reusability and high stability in multiple cycles of degradation. The active species quenching results and electron paramagnetic resonance measurements revealed that SO 4 ·− greatly contributed to organic degradation, while 1O2 and ·OH also involved. Moreover, a series of other transition metal oxides (Co3O4, Fe2O3, Mn3O4, NiO, and CoFe2O4) with hierarchical porous nanosheet structures were successfully fabricated with this method. This study provides a simple, general, and low-cost strategy for fabricating hierarchical porous transition metal oxides, which are promising for the environmental remediation or many other applications in the future.