Synthesis and Characterization of Fe-Imogolite as an Oxidation Catalyst

Ookawa, Masashi

doi:10.5772/48171

Cited by 10 publications

(9 citation statements)

References 44 publications

(68 reference statements)

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“…Natural allophane from Ecuador contains oxalate-soluble Fe that may be present in isomorphic substitution in the allophane, as well as dithionite-extractable Fe present in a finely dispersed goethite phase (Kaufhold et al, 2009(Kaufhold et al, , 2010. The X-ray absorption spectrum (XAS) of Fe-substituted imogolite is distinct from that of Fe-adsorbed imogolite (Ookawa et al, 2006), but the structures have not been fully modeled. According to McBride et al (1984), allophane can accommodate more Fe in its structure than well formed imogolite.…”

Section: Introductionmentioning

confidence: 98%

XAFS Study of Fe-Substituted Allophane and Imogolite

Baker

Nickerson

Strawn

2014

Clays and clay miner.

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The nano-aluminosilicate mineral allophane is common in soils formed from parent materials containing volcanic ash and often contains Fe. Due to its lack of long-range order, the structure of allophane is still not completely understood. In the present study, Fe K-edge X-ray absorption fine structure (XAFS) was used to examine Fe-containing natural and synthetic allophane and imogolite samples. Results indicated that Fe substitutes for octahedrally coordinated Al in allophane, and that Fe exhibits a clustered distribution within the octahedral sheet. Iron adsorbed on allophane surfaces is characterized by spectral features distinct from those of isomorphically substituted Fe and of ferrihydrite. Fe adsorbed on the allophane surfaces probably exists as small polynuclear complexes exhibiting FeÀFe edge sharing, similar to poorly crystalline Fe oxyhydroxides. The XAFS spectra of natural allophane and imogolite indicate that the Fe in the minerals is a combination of isomorphically substituted and surfaceadsorbed Fe. In the synthetic Fe-substituted allophanes, the Fe XAFS spectra did not vary with the Al:Si ratio. Theoretical fits of the extended XAFS (EXAFS) spectra suggest that local atomic structure around octahedral Fe in allophanes is more similar to Fe in a smectite-like structure than to a published theoretical nanoball structure.

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Section: Introductionmentioning

confidence: 98%

XAFS Study of Fe-Substituted Allophane and Imogolite

Baker

Nickerson

Strawn

2014

Clays and clay miner.

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“…The earliest experimental studies on Fe-doped IMO (Ookawa et al 2006;Ookawa 2012) indicated an upper limit to the amount of iron, in that NTs are preserved up to overall 1.4 wt% Fe content. More recent reports on Fe-doped aluminium-germanate NTs, analogous to IMO NTs, showed that Fe IS is indeed limited to 1.0 wt%, and the formation of Fe oxo-hydroxides unavoidably occurs at higher Fe content (Avellan et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Al/Fe isomorphic substitution versus Fe2O3 clusters formation in Fe-doped aluminosilicate nanotubes (imogolite)

et al. 2015

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Textural, magnetic and spectroscopic properties are reported of Fe-doped aluminosilicate nanotubes (NTs) of the imogolite type, IMO, with nominal composition (OH) 3 Al 2-x Fe x O 3 SiOH (x = 0, 0.025, 0.050). Samples were obtained by either direct synthesis (Fe-0.025-IMO, Fe-0.050-IMO) or postsynthesis loading (Fe-L-IMO). The Fe content was either 1.4 wt% (both Fe-0.050-IMO and Fe-L-IMO) or 0.7 wt% (Fe-0.025-IMO). Textural properties were characterized by High-Resolution Transmission Electron Microscopy, X-ray diffraction and N 2 adsorption/ desorption isotherms at 77 K. The presence of different iron species was studied by magnetic moment measurements and three spectroscopies: Mössbauer, UV-Vis and electron paramagnetic resonance, respectively. Fe 3? /Al 3? isomorphic substitution (IS) at octahedral sites at the external surface of NTs is the main process occurring by direct synthesis at low Fe loadings, giving rise to the formation of isolated high-spin Fe 3? sites. Higher loadings give rise, besides IS, to the formation of Fe 2 O 3 clusters. IS occurs up to a limit of Al/Fe atomic ratio of ca. 60 (corresponding to x = 0.032). A fraction of the magnetism related to NCs is pinned by the surface anisotropy; also, clusters are magnetically interacting with each other. Post-synthesis loading leads to a system rather close to that obtained by direct synthesis, involving both IS and cluster formations. Slightly larger clusters than with direct synthesis samples, however, are formed. The

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“…Ookawa and co-workers used Fe-doped INTs for catalytic oxidation with H 2 O 2 of different aromatic hydrocarbons compounds, such as phenol, cyclohexene, benzene, chlorobenzene, or benzaldehyde, to their respective isomers but with low selectivity [87,88]. In a similar approach, Shafia et al followed the degradation of the azo-dye Acid Orange 7 (AO7) in the presence of H 2 O 2 and Fe-doped INTs [89].…”

Section: Catalysis and Fenton Reactionmentioning

confidence: 99%

Metal Chalcogenides Based Heterojunctions and Novel Nanostructures for Photocatalytic Hydrogen Evolution

Jiménez‐Calvo

Paineau

et al. 2020

Catalysts

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The photo-conversion efficiency is a key issue in the development of new photocatalysts for solar light driven water splitting applications. In recent years, different engineering strategies have been proposed to improve the photogeneration and the lifetime of charge carriers in nanostructured photocatalysts. In particular, the rational design of heterojunctions composites to obtain peculiar physico-chemical properties has achieved more efficient charge carriers formation and separation in comparison to their individual component materials. In this review, the recent progress of sulfide-based heterojunctions and novel nanostructures such as core-shell structure, periodical structure, and hollow cylinders is summarized. Some new perspectives of opportunities and challenges in fabricating high-performance photocatalysts are also discussed.

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Synthesis and Characterization of Fe-Imogolite as an Oxidation Catalyst

Cited by 10 publications

References 44 publications

XAFS Study of Fe-Substituted Allophane and Imogolite

XAFS Study of Fe-Substituted Allophane and Imogolite

Al/Fe isomorphic substitution versus Fe2O3 clusters formation in Fe-doped aluminosilicate nanotubes (imogolite)

Metal Chalcogenides Based Heterojunctions and Novel Nanostructures for Photocatalytic Hydrogen Evolution

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