MnO2 Nanosheet Nets on Carbon Fiber as Fixed Catalysts for a Highly Efficient, Nonradical Fenton-like Process in Wastewater Refractory Pollutant Treatment

The development of highly efficient fixed catalysts isa significantconcern in practical wastewater treatment using the peroxymonosulfate(PMS)-based Fenton-like process. In this study, we successfully synthesizeda three-dimensional (3D) & delta;-MnO2 nanosheet (MNSN)net grown on a carbon-fiber (CF) sheet (3D-MNSN-CF) through a simplehydrothermal strategy. This novel catalyst demonstrated exceptionalefficiency and stability in activating PMS for degrading refractoryorganics. The 3D-MNSN-CF catalyst was composed of wrinkled, ultrathin & delta;-MnO2 nanosheets (& SIM;4.3 nm) grown on CF, forminga uniform 3D net structure with a covering thickness of approximately7.6 & mu;m (mass ratio & SIM; 2.17%). This unique morphology provideda fixed Mn-based catalyst with a highly exposed (001) facet, intrinsicMn(3+)/Mn4+ redox pair, and a high ratio of oxygenvacancies (O(V)s). These features enabled the 3D-MNSN-CF/PMSsystem to exhibit a remarkable removal ratio of approximately 100%for tetracycline hydrochloride (TC) degradation. The system also showeda high rate constant (k value) of approximately 0.15min(-1) and a specific activity (& epsilon;) of 3.46L min(-1) g(-1) based on the MnO2 ratio, surpassing many reported Mn-based catalysts. Moreover,the 3D-MNSN-CF catalyst maintained excellent performance over a widepH range from 2 to 11. Furthermore, we discovered that electron-richoxygen-containing groups exhibited an inhibition effect by competingadsorption with PMS, hindering the generation of radicals. Additionally,the results indicated that singlet oxygen (O-1(2)) was the main reactive species responsible for TC removal, whileonly a small amount of radicals contributed to the process. The catalyst'sexcellent performance was also demonstrated in treating various refractoryorganics and real wastewater, and it exhibited splendid stabilityfor recycling use.

Automated summary

This study successfully synthesized a 3D-MNSN-CF catalyst through a simple hydrothermal strategy. The catalyst exhibited exceptional efficiency and stability in activating PMS for degrading refractory organics. It had a highly exposed (001) facet, intrinsic Mn(3+)/Mn4+ redox pair, and a high ratio of oxygen vacancies, resulting in a remarkable removal rate of approximately 100% for tetracycline hydrochloride (TC) degradation.