Effect of rGO Content on Enhanced Photo-Fenton Degradation of Venlafaxine using rGO Encapsulated Magnetic Hexagonal FeTiO3 Nanosheets

In this work, we synthesized magnetic reduced graphene oxide (rGO) encapsulated hexagonal FeTiO3 (FTO@rGO) nanosheets with rGO loading amount of 0, 1, 5 and 10 wt%, with a primary objective of efficiently degrading venlafaxine (VLF) through photo-Fenton processes across a wide pH range of 3-11. The inherent visible-light photocatalytic ability of ilmenite FeTiO3 (FTO) and catalytic activation of H2O2 by Fe sites during the photo-Fenton process were established. Through the strategic integration of rGO, all FTO@rGO catalysts show higher VLF degradation rate than FTO in photo-Fenton evolution experiments and the FTO@rGO catalysts with rGO loading amount of 5 wt% presents the highest VLF degradation rate (100% VLF degradation at 90 min), which attributed to the accelerated migration of photo-generated electrons and the efficient Fe2+/Fe3+ cycle. Furthermore, the encapsulation of rGO significantly mitigated Fe leaching throughout the reaction pH range, directing H2O2 activation to occur at the FTO@rGO interface instead of in solution. Through a comprehensive analysis, we identified 47 intermediate products of VLF and deduced the degradation pathway based on 12 representative intermediates. The degradation process was primarily driven by hydroxyl radicals as the dominant reactive oxygen species, complemented by the contribution of superoxide radicals, photogenerated electrons, and holes during the FTO@rGO-catalyzed photo-Fenton process. This study not only expands the application of ilmenite in the realm of advanced oxidation processes (AOPs) but also provides valuable insights for the future exploration and development of metal oxide/carbonaceous heterostructure catalysts.