UV-Fenton discolouration and mineralization of Orange II over hydroxyl-Fe-pillared bentonite

An efficient solid catalyst, hydroxyl-Fe-pillared bentonite (H-Fe-P-B), was successfully developed for photo-assisted Fenton reaction. The characteristics of the catalyst were detected by N2 adsorption/desorption, X-ray fluorescence spectroscopy (XRF), X-ray powder diffraction (XRD), UV–vis absorption spectra (UV–vis) and atom force microscopy (AFM). The catalytic activity of H-Fe-P-B was evaluated in discolouration and mineralization of Orange II in UV-Fenton system. The effects of pH, Orange II concentration, UV light wavelength and temperature on Orange II degradation were studied in detail. It was found that the catalytic activity of H-Fe-P-B for H2O2 came from Fe-polycations between bentonite sheets rather than Fe3+ or Fe2+ in tetrahedral or octahedral sheets of bentonite. As the leaching of iron from the H-Fe-P-B after treatment was negligible, the H-Fe-P-B exhibited a high catalytic activity and good long-term stability in multiple runs in the discolouration and mineralization of Orange II. Because of the strong surface acidity, the H-Fe-P-B acted as not only catalyst but also solid acid in UV-Fenton system, as a result, almost 100% colour removal and 95% TOC removal of 0.2 mM Orange II could be obtained at 40 and 120 min even if the initial pH of solution was as high as 9.0. These results implied that the H-Fe-P-B was a promising catalyst for UV-Fenton system.