Raschig rings-Fe2O3 composite photocatalyst activate in the degradation of 4-chlorophenol and Orange II under daylight irradiation

Fe2O3 on Raschig glass rings (Fe2O3/RR) was investigated as photocatalyst under simulated solar radiation during the degradation of 4-chlorophenol (4-CP) and the azo dye Orange II (Or II). Thin films of Fe2O3 particles were coated on glass rings using polyethylene-graft-maleic anhydride (PEGMA) as a negative interfacial agent. The Fe2O3/RR photocatalyst presented absorption in the visible range up to 535 nm. The catalytic activity of Fe2O3/RR coated with preformed Fe2O3 (11.4 m2/g) was found to be superior to that of Fe2O3/RR1 catalyst obtained by the precipitation of Fe-ions on the glass rings surface. The photoactivated degradation of 4-CP and Or II was possible at pH values of 5.5 using both catalysts. The Fe2O3/RR photocatalyst shows a stable catalytic performance during long-term operation under simulated sunlight radiation. The Fe2O3/RR and Fe2O3/RR1 photocatalysts were characterized by diffusion reflectance spectroscopy (DRS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS) and gas adsorption measurements (BET). The Fe 2p binding energy (BE) in the Fe2O3/RR samples was 711.6 eV before the catalysis and 711.7 eV after the catalysis, indicating the stability of the Fe-oxidation state on the glass rings. The pore diameter did not decrease when going from Fe2O3 powder to the Fe2O3 attached on the Raschig glass rings but the Fe2O3 BET area decreased considerably involving restructuring of the Fe2O3 particles. The experimental data allows to formulate a mechanism of reaction for the degradation of 4-CP on the Fe2O3/RR catalyst.