In-situ formation of magnetic sodium ferric silicate/ferric oxide S-scheme heterojunction with efficiently removing tetracycline in photo-Fenton-like reaction

The improvement of Fe(III)/Fe(II) conversion efficiency and facilitation for recycling of Fe-based catalyst have dual economic and green benefits in the field of photo-Fenton-like for wastewater treatment. To achieve those purposes, we have designed and fabricated an S-scheme catalyst by in-situ growing magnetic sodium ferric silicate/ferroferric oxide-ferric oxide (SFS/M-FO) heterojunction. Our results demonstrated the mechanism of heterogeneous interface formation and S-scheme charge transportation between NaFeSi2O6 and α-Fe2O3 in the composite. Meanwhile, the semi-coherent interface in heterojunction could effectively reduce the charge transfer resistance. The incorporation of magnetic ferroferric oxide (Fe3O4) not only ensured high recoverability of the catalyst, but also facilitated charge transfer and improved light absorption capacity. The improved catalytic activity was derived from the combination of the S-scheme NaFeSi2O6/α-Fe2O3 heterojunction and Fe3O4 electronic conductor. Therefore, the SFS/M-FO composite showed excellent tetracycline removal rate of 91.8% within 50 min in the photo-Fenton-like reaction. The ternary composite also held excellent performance, reusability and structural stability. The produced intermediates and three degradation pathways of tetracycline were identified by liquid chromatograph-mass spectrometer. This study offers a convenient way for combining high performance and magnetical retrievability by in-situ growth method for wastewater treatment.