Photocatalysis-Fenton of Fe-doped g-C3N4 catalyst and its excellent degradation performance towards RhB

A Fe-doped graphite-like carbon nitride (g-C3N4) nanocomposites containing various Fe contents (5 wt.%, 10 wt.% and 15 wt.%) were prepared via two-step calcination thermal polymerization, and were employed as efficient heterogeneous photo-Fenton composites towards rhodamine B (RhB) removal in visible-light/H2O2 system. The sheet structure of g-C3N4 was refined down to nano-scale and less densely packed by the increasing Fe-doping ratio. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra indicated that Fe was doped completely into the g-C3N4 lattice. Over 90 %RhB was degraded in photo-Fenton system within 45 min under the optimal Fe-doping ratio of 10 wt.% (10 % Fe-g-C3N4). The degradation efficiency of photo-Fenton was superior in comparison with photocatalysis and Fenton reaction. The as-prepared composite exhibited excellent performance (∼90 % removal) and high stability in a wide range of pH value (3∼9), and the degradation data well fitted with the pseudo-first-order kinetics model. The enhanced photo-Fenton catalytic activity benefited from the Z-scheme heterojunctions of Fe-g-C3N4, which improved the separation ability of photo-generated charge carriers and increased the electrons that participated in Fe2+/Fe3+ cycle. The main active oxygen species of Fe-g-C3N4 were hydroxyl radicals, followed by superoxide radicals and electron holes. The effect of Fe-doping was revealed by density functional theory calculation. The excellent recyclability and stability of Fe-g-C3N4 catalyst was also observed. Such photo-Fenton system was also effective to degrade other organic pollutants. The findings reported here offer promising implications in developing the utilization of Fe-g-C3N4 composite in photo-Fenton system for treatment of wastewater.