Photocatalytic degradation of 2,4,6-tribromophenol over Fe-doped ZnIn2S4: Stable activity and enhanced debromination

Fe doped ZnIn2S4 catalyst was prepared and tested for photocatalytic degradation of 2,4,6-tribromophenol (2,4,6-TBP), it was more efficient in debromination and total organic carbon (TOC) removal, compared with TiO2 (P25) and ZnIn2S4. The preparation of Fe-ZnIn2S4 involved a facile hydrothermal ZnIn2S4 synthesis process at low temperature and without templates, followed by chemical reductive deposition of Fe. The catalysts were characterized using scanning electron microscopy (SEM) equipped with an X-ray energy dispersive spectroscopy (EDS), TEM and HRTEM, FT-IR spectra, X-ray diffraction (XRD) and UV–vis diffuse reflectance spectra. The band gaps of ZnIn2S4 and Fe-ZnIn2S4 calculated from the onset of the absorption edges were 2.12 eV and 2.05 eV, respectively. The calculated pseudo-first-order constants (Kr) were in the order of TiO2 (0.022 min−1) < 0.5 wt% Fe-TiO2 (0.0369 min−1) < ZnIn2S4 (0.362 min−1) < 0.5 wt% Fe-ZnIn2S4 (0.436 min−1). After 1 h reaction by Fe-ZnIn2S4, the released bromide concentration was 17.6mg l−1, which was 1.11 and 2.69 times higher than ZnIn2S4 and TiO2 (P25), respectively. The increase in TOC removal was 7% and 33% compared to ZnIn2S4 and TiO2 (P25), respectively. The repeated tests proved that the synthesized Fe-ZnIn2S4 was stable, reusable and durable in degradation of 2,4,6-TBP. The possible cycle of iron species and a tentative debromination pathway were proposed.