A Fe-N/FeS@C composite prepared via mechanical activation and pyrolysis for sulfite activation to degrade organic contaminants: Single atomic irons anchored into carbon matrix with encapsulated FeS nanoparticles. Issue 6 (December 2021) - Wu, Juan
Abstract: A novel structural composite (Fe-N/FeS@C) was synthesized via a self-doping strategy by the pyrolysis of a solid mixture of lignosulfonate and ferric nitrate pretreated by mechanical activation. The as-synthesized composite contained 7.5 wt% of single atomic iron moieties and 16.0 wt% of encapsulated FeS nanoparticles, with a high surface area of 1095.81 m 2 g –1 and plentiful micropores and mesopores (0.4–10 nm). The Fe-N/FeS@C composite was confirmed to possess outstanding catalytic activity for sulfite activation in the degradation of methylene blue, with a high reaction rate constant (0.77 g g –1 min –1 ) and long cycling stability (83.1% of initial activity retention after 10 recycles). Moreover, the composite exhibited satisfactory activity recovery via a simple rinsing process with ethanol and HCl, and performed well in a wide pH range of 3–11. Density functional theory calculation results further demonstrated that the reaction energy of the rate-determining step, in which SO3 − was produced from SO3 2– on atomic Fe moieties, was lower than that of the formation of FeSO3 + by Fe 3+ and SO3 2– . The excellent performance of Fe-N/FeS@C was mainly attributed to the combination of the high mass loading of active sites of atomic Fe moieties anchored into carbon matrix with encapsulated FeS nanoparticles. This study provides new insight into the development of environment-friendly, stable and atomic dispersion iron composite for sulfite activation to efficiently remove organic pollutants. Graphical Abstract: ga1 Highlights: A composite (Fe-N/FeS@C) was developed by MA and pyrolysis technology. Activation of sulfite using the composite exhibits a superior catalytic activity. Both SO4 − and OH are identified as the main reactive oxygen species. Single atomic irons and encapsulated FeS in the catalyst are key active sites.