Mössbauer and X-ray study of natural magnetite sands

The study of natural magnetic sands is instrumental to investigate the geological aspects of their formation and of the origin of their territory. In particular, Mössbauer spectroscopy provides unique information on their iron content and on the oxidation state of iron in their mineral composition. The Italian coast on the Mediterranean Sea near Rome is known for the presence of highly magnetic black sands of volcanic origin. A study of the room temperature Mössbauer spectrum, powder X-ray diffraction, energy dispersive X-ray spectroscopy, and magnetic measurements of a sample of black magnetic sand collected on the seashore of the town of Ladispoli is performed. This study reveals magnetite as main constituent with iron in both tetrahedral and octahedral sites. Minor constituents are the iron minerals hematite and ilmenite, the iron containing minerals diopsite, gossular, and allanite, as well as ubiquitous sanidine, quartz, and calcite.

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“…[2,3]. To analyze the spectrum, fits have been performed starting from the simplest hypothesis of two sextets.…”

Section: Resultsmentioning

confidence: 99%

“…For substances containing iron, Mössbauer spectroscopy represents the most precise and predictive method [1]. This is the case of magnetic sands, as reported in studies of sands from the Black Sea [2] and from Costa Rica [3]. Several studies have been published on Mössbauer spectroscopy of volcanic soils (see for ex.…”

Section: Introductionmentioning

confidence: 99%

Mössbauer, X-ray and Magnetic Studies of Black Sand from the Italian Mediterranean Sea

Braccini¹,

Pellegrinelli²,

Krämer³

2013

WJNST

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“…This fit routine includes two additional sextets corresponding to maghemite for all of these samples. It is very much objectionable considering that at RT the sextets arising from ferric ions of the octahedral and tetrahedral sites largely overlap and are inseparable because of poor resolution. − Hence, the maghemite Mossbauer spectrum should only be fitted with a sextet, although it can better resolve if collected at lower temperatures , and/or upon application of a magnetic field. ,− Moreover, in this particular case, it is very significant, as the obtained hyperfine parameters of the magnetite tetrahedral site, both sites of maghemite and hematite are in a very narrow range, with the hyperfine field of these samples lying in the range of 49.5–51.7 T (Table S4). Hence, attempting to fit a two-sextet model for maghemite in these spectra is not acceptable for all practical purposes.…”

Section: Introductionmentioning

confidence: 99%

Comment on “Engineering Shape Anisotropy of Fe₃O₄-γ-Fe₂O₃ Hollow Nanoparticles for Magnetic Hyperthermia”

Nayak

2022

ACS Appl. Nano Mater.

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In a recent paper, the authors presented their investigation involving engineering shape anisotropy of Fe3O4-γ-Fe2O3 hollow nanoparticles for magnetic hyperthermia; however, a significant part of the study involving Mössbauer spectroscopy is erroneous. During analysis of the room temperature Mössbauer spectra for these samples, the investigators included two additional sextets for γ-Fe2O3 (maghemite). This is not acceptable considering that the sextets arising from ferric ions of both the octahedral and tetrahedral sites of maghemite largely overlap at room temperature and are inseparable because of poor resolution. We suggest a methodology for analyzing these spectra, and accordingly corrections are warranted in Figure 4 and Tables S3 and S4 and within the main text.

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“…The Mössbauer spectra of the iron oxide samples are shown in , respectively, and these can be assigned to c-Fe 2 O 3 [15][16][17][18][19]. The sextet of sub-spectrum 2 having an I.S.…”

Section: Mössbauer Spectrum Analysis For the Iron-based Catalystsmentioning

confidence: 99%

Low‐Temperature De‐NO_x by Selective Catalytic Reduction Based on Iron‐Based Catalysts

2010

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Low-temperature De-NO x technology is a new topic in the area of flue gas treatment. This paper presents experimental studies on selective catalytic reduction (SCR) of NO x from synthetic flue gas over iron-based catalysts with ammonia in a fluidized reactor. The iron-based catalysts used in the experiments are particles of Fe 3 O 4 and c-Fe 2 O 3 , and they are analyzed by X-ray diffraction (XRD) and Mössbauer spectroscopy, before and after reaction. It is observed that the efficiency of De-NO x with c-Fe 2 O 3 catalyst is high at temperatures from 200-290°C and the maximum efficiency is seen to exceed 90 % at 250°C. The effects of magnetic fields on SCR De-NO x using c-Fe 2 O 3 particles as catalysts are also studied by applying uniform and coaxial magnetic fields to the fluidized bed. The results suggest that SCR De-NO x on c-Fe 2 O 3 catalyst is fit for operation below 200°C in the fluidized reactor in conjunction with the effects of magnetic fields. IntroductionSelective catalytic reduction (SCR) of NO x is an effective flue gas cleaning technology, which can reduce NO x with high efficiency [1][2][3]. Currently, SCR De-NO x is normally undertaken at medium to high temperatures varying from 350-450°C. However, the temperature of the flue gas discharged from the boiler is reduced to 200°C, since the flue gas cools down when it passes through the boiler economizer and the air preheater. Therefore, it is difficult for the tail end configurations to apply SCR De-NO x technologies developed under middle to high temperature conditions in practical situations. Moreover, the De-NO x catalysts can be poisoned by SO 2 , and thus, one should remove SO 2 in the flue gas before the De-NO x process proceeds. Unfortunately, the temperature of the flue gas after desulfurization is normally below 200°C. In such instances, if the operation temperatures of De-NO x catalysts are in the medium to high temperature range, the flue gas must be reheated by heat exchange, and this results in even further energy consumption. Hence, it is important to develop a low temperature De-NO x technology and determine the catalysts that can be used in such low temperature De-NO x processes. However, most of the suitable catalysts currently available are expensive metal oxides, e.g., Mn-based [4-8], Cu-based [9][10][11][12], and Cebased [3,13] catalysts. In addition to the high costs involved in applying these metal-based catalysts to industry, the heavy metal-based catalysts will cause further pollution to the environment if their disposal is not undertaken properly.Therefore, in the current context, the SCR De-NO x from synthetic flue gas is investigated in a fluidized reactor based on magnetic iron-based catalysts, such as Fe 3 O 4 and Fe 2 O 3 . These iron-based catalysts are fairly cheap and less hazardous compared to the above-mentioned metal oxide catalysts. Furthermore, a magnetically fluidized bed is configured by applying uniform and axial magnetic fields to the fluidized bed, and the effects of magnetic fields on SCR De-NO x are rese...

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Mössbauer and X-ray study of natural magnetite sands

Cited by 6 publications

References 4 publications

Mössbauer, X-ray and Magnetic Studies of Black Sand from the Italian Mediterranean Sea

Mössbauer, X-ray and Magnetic Studies of Black Sand from the Italian Mediterranean Sea

Comment on “Engineering Shape Anisotropy of Fe₃O₄-γ-Fe₂O₃ Hollow Nanoparticles for Magnetic Hyperthermia”

Low‐Temperature De‐NO_x by Selective Catalytic Reduction Based on Iron‐Based Catalysts

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Mössbauer and X-ray study of natural magnetite sands

Cited by 6 publications

References 4 publications

M&#246;ssbauer, X-ray and Magnetic Studies of Black Sand from the Italian Mediterranean Sea

M&#246;ssbauer, X-ray and Magnetic Studies of Black Sand from the Italian Mediterranean Sea

Comment on “Engineering Shape Anisotropy of Fe3O4-γ-Fe2O3 Hollow Nanoparticles for Magnetic Hyperthermia”

Low‐Temperature De‐NOx by Selective Catalytic Reduction Based on Iron‐Based Catalysts

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Product

Resources

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Mössbauer, X-ray and Magnetic Studies of Black Sand from the Italian Mediterranean Sea

Mössbauer, X-ray and Magnetic Studies of Black Sand from the Italian Mediterranean Sea

Comment on “Engineering Shape Anisotropy of Fe₃O₄-γ-Fe₂O₃ Hollow Nanoparticles for Magnetic Hyperthermia”

Low‐Temperature De‐NO_x by Selective Catalytic Reduction Based on Iron‐Based Catalysts