Enhanced heterogeneous Fenton catalysis by carbon nanotube-loaded Mn doped FeS2 catalysts for pollutant degradation: Co-enhancement effect of Fe-S-Mn and Fe-S-C linkages

Recently, pyrite (FeS2) has been discovered as a promising heterogeneous Fenton catalyst due to the excellent generation of Fe(II). However, the limited inherent catalytic efficiency and poor stability hinder its wide application in wastewater treatment. Herein, a novel carbon nanotube-loaded Mn-doped FeS2 (Mn-FeS2/MWCNT) catalyst was synthesized for high radical production and durable Fenton catalysis. The optimized Mn-FeS2/MWCNT exhibited 100 % of bisphenol A elimination within 15 min, which was ∼174- and ∼20-fold than that of FeS2 and FeS2/MWCNT, respectively, and Mn-FeS2/MWCNT demonstrated remarkable stability after five cycles (less than 0.8 mg/L Fe leaching in each cycle). The generation of hydroxyl radicals (OH) and superoxide radicals (O2−) was enhanced with Mn doping and the introduction of MWCNTs. Mechanistic studies and DFT calculations revealed that Mn doping tuned the electron density between Fe and Mn in the Fe–S–Mn linkage, further improving the H2O2 absorption energy on the Mn-FeS2 surface for radical generation. Introducing MWCNTs improved the reactivity and stability of the catalyst by electron transfer of the Fe–S–C bond. This work determined the co-enhancement effect of metal sulfur links and sulfur carbon bonds on pyrite-based materials and provides a promising catalyst for wastewater remediation.