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

Abstract Fe 2 O 3 on Raschig glass rings (Fe 2 O 3 /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 Fe 2 O 3 particles were coated on glass rings using polyethylene-graft-maleic anhydride (PEGMA) as a negative interfacial agent. The Fe 2 O 3 /RR photocatalyst presented absorption in the visible range up to 535 nm. The catalytic activity of Fe 2 O 3 /RR coated with preformed Fe 2 O 3 (11.4 m 2 /g) was found to be superior to that of Fe 2 O 3 /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 Fe 2 O 3 /RR photocatalyst shows a stable catalytic performance during long-term operation under simulated sunlight radiation. The Fe 2 O 3 /RR and Fe 2 O 3 /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 Fe 2 O 3 /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 Fe 2 O 3 powder to the Fe 2 O 3 attached on the Raschig glass rings but the Fe 2 O 3 BET area decreased considerably involving restructuring of the Fe 2 O 3 particles. The experimental data allows to formulate a mechanism of reaction for the degradation of 4-CP on the Fe 2 O 3 /RR catalyst.