FeS2-Fe1-xS heterostructure as a high-efficient Fenton-like catalyst for ultrafast degradation of orange II

It is a challenge to develop heterogeneous Fenton-like catalysts with excellent performance and stability in the field of wastewater treatment. In this work, the FeS2-Fe1-xS heterostructure catalyst was prepared by solvothermal method through adding cobalt element to change the particle nucleation process and inhibit the transformation process of pyrrhotite (Fe1-xS) phase to pyrite (FeS2) phase. Then, a series of experiments were devised to clarify the catalytic activity of FeS2-Fe1-xS heterostructure. The degradation experiments exhibited that 99.9% degradation efficiency was achieved for 30 mg/L orange II solution within 15 min at the conditions of 0.2 g/L FeS2-Fe1-xS, 2 mM H2O2 and pH = 3.0. In addition, the reusability of the FeS2-Fe1-xS catalyst was also investigated and the result displayed that degradation efficiency of orange II can reach 95.2% after eight cycles. The degradation of orange II was enhanced by Fenton reaction between FeS2-Fe1-xS and dissolved oxygen, which could smoothly release Fe2+ and Fe3+ for the activation of H2O2 to produce more hydroxyl radicals. Finally, the degradation pathway of orange II was proposed by detecting intermediates produced in FeS2-Fe1-xS/H2O2 photo-Fenton-like system by liquid chromatography-mass spectrometry (LC-MS). In short, FeS2-Fe1-xS is a promising catalyst for removing the organic pollutants from solutions.