Ultrathin Cu-Fe oxide nanosheets boosting persulfate activation to remove organic pollutants with coupling and transformation between radical and nonradical mechanism

Abstract

Transitional metal oxides with lamellar feature are desirable catalysts towards peroxydisulfate (PDS) activation for wastewater treatment. However, the feasibility and mechanism of PDS activation by Cu-Fe bimetallic nanosheets are barely explored. Herein, novel ultrathin Cu-Fe oxide nanosheets (CuFe-OS) were constructed by fast reduction for efficient PDS activation. Assembled by intercrossing nanosheets with about 4 nm thickness, Cu1Fe1-OS possessed regular crystal texture, multiple metal–oxygen bonds, and abundant oxygen vacancies, distinguishing from the amorphous Cu-Fe oxide (CuFe-O). Such features of Cu1Fe1-OS contributed to a 62.40 % increase of typical organic pollutant (acid orange 7) removal efficiency and 13.47 times improvement of degradation rate constant, compared to Cu1Fe1-O. Furthermore, the coupling function of radical and nonradical pathways drove the Cu1Fe1-OS activation process, with 1O2 and ⋅O2− as the primary reactive oxygen species. The 1O2 was principally generated from the recombination of ⋅O2−, manifesting the transformation from radical to nonradical mechanism in the Cu1Fe1-OS/PDS system. Abundant oxygen vacancies benefited the generation of ⋅O2− and the conversion of metallic ions. The bimetallic synergy in Cu1Fe1-OS boosted the reversible redox cycles of Fe3+/Fe2+ and Cu2+/Cu+. This work provides a novel strategy of persulfate activation for wastewater remediation and deepens the understanding of coupled radical and nonradical mechanisms.