Abstract
The x-SnO2/α-Fe2O3 (x = 0.04, 0.07, and 0.1) heterogeneous composites were successfully prepared via a two-step solvothermal method. These composites were systematically characterized by the X-ray diffraction technique, field emission scanning electron microscopy, an energy dispersive spectrometer, X-ray photoelectron spectroscopy and a UV–visible spectrometer. It was found that SnO2 nanoparticles were uniformly decorated on the surface of α-Fe2O3 particles in these heterogeneous composites. A comparative study of methylene blue (MB) photodegradation by α-Fe2O3 and x-SnO2/α-Fe2O3 composites was carried out. All x-SnO2/α-Fe2O3 composites showed higher MB photodegradation efficiency than α-Fe2O3. When x = 0.07, the MB photodegradation efficiency can reach 97% in 60 min. Meanwhile, the first-order kinetic studies demonstrated that the optimal rate constant of 0.07-SnO2/α-Fe2O3 composite was 0.0537 min−1, while that of pure α-Fe2O3 was only 0.0191 min−1. The catalytic mechanism of MB photodegradation by SnO2/α-Fe2O3 was examined. The SnO2 can act as a sink and help the effective transfer of photo-generated electrons for decomposing hydrogen peroxide (H2O2) into active radicals. This work can provide a new insight into the catalytic mechanism of the photo-Fenton process.
Highlights
As an important advanced oxidation process, the heterogeneous photo-Fenton system has been considered a promising method for the removal of stubborn organic dyes [1–4]
The crystal structure of as-prepared α-Fe2 O3 precursors, SnO2, and x-SnO2 /α-Fe2 O3 (x = 0.04, 0.07, and 0.1) powders were measured by X-ray diffraction (XRD)
The widths of peaks of SnO2 are much larger than that of α-Fe2 O3, which might be attributed to the poor crystallinity and small particle size of SnO2
Summary
As an important advanced oxidation process, the heterogeneous photo-Fenton system has been considered a promising method for the removal of stubborn organic dyes [1–4]. In this process, iron-based catalysts are generally applied to activate H2 O2 in order to generate strong oxidative hydroxyl radicals (·OH) [5–8]. Several adverse factors seriously reduce the reaction activity of α-Fe2 O3 , such as the high recombination rate of photoelectrons and holes, and a weak activation in alkaline environments To remedy these drawbacks, various measures have been studied, such as porous regulation [11–16], facet engineering [17–20], and composite construction [21–26]. Free radical trapping experiments and hydroxyl radical quantitative experiments were carried out to explore the mechanism of photocatalytic reaction
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