Preparation of Si–Al/α-FeOOH Catalyst from an Iron-Containing Waste and Surface–catalytic Oxidation of Methylene Blue at Neutral Ph Value in the Presence of H2O2

The tested Si–Al/α-FeOOH composite was prepared by dissolution, precipitation and aging of a high iron-containing grinding wheel ash (GWA). The obtained Si–Al/α-FeOOH composite was characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope/energy dispersive X-ray spectrometer (SEM/EDS) analyses. The characterized composite was then evaluated for the decolorization of methylene blue (MB) in the presence of H2O2 at various pH conditions. The extent of MB decolorization was characterized using UV–Vis spectra, total organic carbon (TOC) and Fourier transform infrared spectroscopy (FTIR). The surface–catalytic oxidation mechanism was discussed and the roles of silica and alumina were also evaluated through preparation of four kinds of catalysts from analytical reagents (ARs). The results showed that α-FeOOH (75.40wt% Fe) was the predominate content in Si–Al/α-FeOOH composite with 2.26wt% Si and 1.02wt% Al. The Fenton-like process (Si–Al/α-FeOOH composite combined with H2O2) can effectively oxidize MB at pH 6.46% and 72% of TOC removal can be achieved after 60min catalytic oxidation. The surface–catalytic oxidation by Si–Al/α-FeOOH/H2O2 may proceed mainly through a non-radical mechanism. The introduction of silica played an important role in the enhancement of the α-FeOOH adsorptive capacity by the inhibition of the formation of crystalline structure of FeOOH, and the introduction of alumina might enhance the α-FeOOH catalytic activity and also prevent the iron from leaching from Si–Al/α-FeOOH catalyst.