Comparative study of catalytic activity of different Fe-pillared bentonites in the presence of UV light and H2O2

To study the relationship of catalytic activity with Fe configuration over bentonite, three kinds of Fe-pillared bentonites were prepared by pillaring the bentonite with different Fe configurations (Fe-polycation, α-Fe2O3 and α-FeOOH). The characteristics of Fe-pillared bentonites were detected by N2 adsorption/desorption, XRF, XRD, FTIR, AFM and UV–vis. Their catalytic activities were compared by discoloration and mineralization of Orange II in the presence of UV light and H2O2. The order of catalytic activity of Fe-pillared bentonites for dye discoloration was α-Fe2O3-pillared bentonite (α-Fe2O3-P-B) > hydroxyl-Fe-pillared bentonite (H-Fe-P-B) > α-FeOOH-pillared bentonite (α-FeOOH-P-B). And that for dye mineralization was α-Fe2O3-P-B = H-Fe-P-B ≫ α-FeOOH-P-B. A possible catalytic mechanism was proposed for surface and solution reactions to discuss the difference in their catalytic activities. The rate constants of UV-Fenton reaction decreased but the catalytic activities of Fe-pillared bentonites for H2O2 became more obvious when the UV light wavelength increased. Furthermore, the reaction activation energy of UV-Fenton reaction was 18.6 kJ mol−1, 20.1 kJ mol−1 and 23.9 kJ mol−1 with catalyst of H-Fe-P-B, α-Fe2O3-P-B and α-FeOOH-P-B, respectively. The results showed that both α-Fe2O3-P-B and H-Fe-P-B were promising catalysts for UV-Fenton system because of its physical and chemical stability and highly catalytic activity.