Fabrication of 2D TiO2/α-Fe2O3/Fe-g-C3N4 heterogeneous from metallurgical solid waste for Photo-Fenton catalysis of levofloxacin/Cr(VI): Electron transfer pathway and DFT calculation

Abstract

Herein, the 2D Nano α-Fe2O3 were prepared by solvent-free method from rolling iron scale (RIS) - a by-product of metallurgical industry. 2D TiO2/α-Fe2O3 nanostructures were prepared using the obtained nanocrystals. Fe-doped g-C3N4 (Fe-g-C3N4) was synthesized using RIS as the raw material. A Composite of TiO2/α-Fe2O3 and Fe-g-C3N4 was combined to prepare a TiO2/α-Fe2O3/Fe-g-C3N4 heterojunction with high catalytic performance. This heterojunction was employed as a photo-Fenton catalyst to synergistically remove Cr(VI) and levofloxacin (LEV). The TiO2/α-Fe2O3/Fe-g-C3N4 heterojunction enhanced the intensity of the visible light response and suppressed the recombination of photogenerated electrons and holes. The N-Fe-O bridge, formed by synergistic coordination effects, enhanced the charge lifetime by decreasing the impedance of the catalyst and increasing the electron transfer rate. Additionally, the Fermi level and work function of the sample were calculated, providing further evidence for the electron transfer. Direct electron transfer between TiO2/α-Fe2O3/Fe-g-C3N4 and LEV/Cr(VI) was observed, indicating its importance in the removal of pollutants. To determine the potential degradation pathways, the energy orbitals of LEV derived from DFT calculations were analyzed. Overall, the study presents an excellent strategy for the sustainable use of RIS and the preparation of highly active catalysts. In conclusion, TiO2/α-Fe2O3/Fe-g-C3N4 is predicted to considerably contribute to studies on treating heavy metal and organic pollutant-contaminated wastewater.