Increasing the efficiency of magnetic heterogeneous Fenton catalysts with a simple halogen visible lamp

Abstract

The effect of a simple visible halogen lamp was studied in the Fenton-type oxidation of three model aqueous pollutants differing in their structure and electrostatic charge, methylorange (MO), methylene blue (MB) and paranitrophenol (PNP), using maghemite nanoparticles (γ-Fe 2 O 3 NP), or maghemite/silica nanocomposite microspheres (γ-Fe 2 O 3 /SiO 2 MS) as heterogeneous catalysts. These materials, which were fully characterized, differ in size, morphology, porosity and microstructure, although their catalytic activity is related to the same γ-Fe 2 O 3 nanoparticles. Both have a strong magnetic susceptibility, but only the MS catalyst can be easily recovered by magnetic settlement. Whatever the catalyst, the pollutant tested, or the experimental conditions used, much better decolorization rates and mineralization efficiencies were recorded under illumination by visible light in comparison to the same tests in the dark. The large range of experimental conditions tested enabled us to propose a mechanism for photocatalytic activity. Experiments of long-term stability showed that the MS catalyst, although generally less active than the NP catalyst, retained almost all of its activity after five repeated experiments under visible light. The good stability of this catalyst was also confirmed by the low level of iron leaching, making it suitable candidate for an application as photo-Fenton catalyst in industrial wastewater treatment.

Fe3+-doped ordered mesoporous γ-Fe2O3/SiO2 microspheres as a highly efficient magnetically separable heterogeneous Fenton catalyst

“…We also observed a low level of leaching and a good reusability for this catalyst, but relatively low activities, and moderate mineralization levels, were obtained in the absence of light [20,35]. However, we reported that the efficiency of this material can be improved through the use of visible light [34]. But photoactivation is not always practicable at a large scale, or when the effluent is characterized by a high level of turbidity or absorbance [36].…”

“…The γ-Fe 2 O 3 NPs used in this study were the same as those used in our previous papers [20,34,35]. The first step is the coprecipitation of Fe 2+ and Fe 3+ ions in order to get magnetite (Fe 3 O 4 ) NPs [37].…”

“…The undoped maghemite/silica microporous microspheres (γ-Fe 2 O 3 /SiO 2 MS) were synthesized using a modified ESE (emulsion solvent evaporation) protocol [39] described in our previous papers [20,34,35]. Briefly, a silica precursor (tetraethoxysilane, TEOS, 20 mL) was hydrolyzed by stirring during 45 min with a 0.15 mol L −1 HNO 3 aqueous solution (5 mL).…”

“…In our previous studies, we employed maghemite (γ-Fe 2 O 3 ) nanoparticles (NPs) supported on microporous silica microspheres as heterogeneous Fenton catalysts [20,34,35]. The main advantage of this material is to be easily recoverable with the help of a simple magnet, as a result of the high magnetic susceptibility of the γ-Fe 2 O 3 NPs.…”

Advanced applications of chemo‐responsive dyes based odor imaging technology for fast sensing food quality and safety: A review

“…are the major factors in the selection of the camera light source. The commonly used light sources are halogen lamps (fiber light sources), high frequency fluorescent lamps, and LED light sources (Ferroudj et al., 2017; X. Zhou et al., 2010). For example, Zhang et al.…”