Maghemite nanoparticles and maghemite/silica nanocomposite microspheres as magnetic Fenton catalysts for the removal of water pollutants

Abstract

Maghemite nanoparticles (γ-Fe 2 O 3 NP), and maghemite/silica nanocomposite microspheres (γ-Fe 2 O 3 /SiO 2 MS), have been evaluated as magnetic heterogeneous Fenton catalysts. The catalysts were fully characterized by electronic microscopies, magnetometry, XRD, UV-Vis-NIR spectroscopy, and sorption volumetry. It was found that the two materials differ in size, morphology, porosity and microstructure, although the maghemite nanoparticles are not modified by their encapsulation into the silica. Both catalysts have a strong magnetic susceptibility, but only the MS catalyst can be easily recovered by magnetic settlement. The mineralization and decolorization of aqueous solutions containing a model pollutant in presence of the catalysts were comparatively studied. Three model pollutants differing in their structure and their electrostatic charge were tested. The obtained reaction rates depend on the nature of the pollutant and catalyst. The results indicate the existence of a correlation between the amount of adsorbed pollutant and the decolorization rate. The free NP are usually more active than the MS catalyst, but larger velocity can also be obtained with the MS catalyst when the pollutant is strongly adsorbed on this material. Moderate mineralization rates were observed for both catalysts illustrating the larger stability toward oxidation of the uncoloured organic intermediates resulting from the primary degradation of the model pollutants. Moreover the efficiency and stability of the MS catalyst were established since this material showed an activity for a pollutant during five consecutive tests. This was also confirmed by characterization of the catalyst after these tests.

Recent advances and prospects of catalytic advanced oxidation process in treating textile effluents

“…The synthesized γ-FeOOH-GAC nanocomposites had low leaching rate; therefore, they could be used for a long time. Additionally, maghemite (γ-Fe 2 O 3 ) nanoparticles and γ-Fe 2 O 3 /silica nanocomposite microspheres were evaluated as magnetic heterogeneous Fenton catalysts for the degradation of MB, MO, and paranitrophenol by Ferroudj et al (2013). The developed nanoparticles maintained a good activity for MO degradation in five repeated experiments despite a relative decrease in the reaction rates.…”

“…Recently, nanostructured materials have gained enormous attention in wastewater treatment through AOPs (Nezamzadeh-Ejhieh and Banan 2011, Ferroudj et al 2013, He et al 2014. Least diffusion resistance, easy accessibility to reactants, and availability of a large number of active sites are among the advantages compared to micro-and macrosized particles in chemical processes especially for wastewater treatment.…”

Metallo-Solid Lipid Nanoparticles as Colloidal Tools for Meso–Macroporous Supported Catalysts

“…Among them, silica-supported iron oxide has been intensively studied for wastewater treatment such as degradation of organic dyes through Fenton-like reactions. [11][12] Mesoporous silica has been also widely studied as a support material due to its high pore volume, surface area as well as ordered pore network which provide a good active site accessibility. [13][14] Several studies have proven that iron oxide dispersed in mesoporous silica supports shows not only a considerable improvement of catalytic ability, but also better stability of iron oxide, compared to free iron oxide particles.…”

Colloidal cubes for the enhanced degradation of organic dyes

“…This result was probably effected by the combination of the adsorption of both methylene blue and hydrogen peroxide to the silica surface, and the inherent acidity of the silica surface, as proposed in previous studies. 20,23,44,45 The former brings the reactants closer to the hematite surface. The latter is benecial since the Fenton reaction is enhanced at low pH.…”