Environmental application of millimetre-scale sponge iron (s-Fe0) partiCles (IV): New insights into visible light photo-Fenton-like process with optimum dosage of H2O2 and RhB photosensitizers

In this study, we firstly develop the photo-Fenton-like system with millimetric sponge iron (s-Fe-0), H2O2, visible light (vis, lambda >= 420 nm) and rhodamine B (RhB), and present a comprehensive study concerning the mechanism. Thus, we investigate (1) the adsorption of RhB onto s-Fe-0 (2) the photo-Fenton-like removal of RhB over iron oxides generated from the corrosion of s-Fe-0 (3) the homogeneous photo Fenton removal of RhB over Fe2+ or Fe3+, (4) the Fe3+-RhB complexes, and (5) the photo-Fenton-like removal of tetrabromobisphenol A (TBBPA). The results show that neither the adsorption process over s-Fe-0 nor the photo-Fenton-like process over FeOOH, Fe3O4 and Fe2O3, achieved efficient removal of RhB. For comparison, in homogeneous photo Fenton process, the presence of Fe3+ ions, rather than Fe2+ ions, effectively eliminated RhB. Furthermore, the UV-vis spectra showing new absorbance at similar to 285 nm indicate the complexes of RhB and Fe3+ ions, adopting vis photons to form excited state and further eject one electron via ligand-to-metal charge transfer to activate H2O2. Additionally, efficient TBBPA removal was obtained only in the presence of RhB. Accordingly, the s-Fe-0-based photo-Fenton-like process assisted with dyestuff wastewater is promising for removing a series of persistent organic pollutants. (C) 2016 Elsevier B.V. All rights reserved.