Environmental application of millimetre-scale sponge iron (s-Fe 0 ) particles (IV): New insights into visible light photo-Fenton-like process with optimum dosage of H 2 O 2 and RhB photosensitizers

In this study, we firstly develop the photo-Fenton-like system with millimetric sponge iron (s-Fe0), H2O2, visible light (vis, λ≥420nm) and rhodamine B (RhB), and present a comprehensive study concerning the mechanism. Thus, we investigate (1) the adsorption of RhB onto s-Fe0, (2) the photo-Fenton-like removal of RhB over iron oxides generated from the corrosion of s-Fe0, (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-Fe0 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∼285nm 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-Fe0- based photo-Fenton-like process assisted with dyestuff wastewater is promising for removing a series of persistent organic pollutants.