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 similar to 174- and similar to 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 (O-2(-)) 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.