Reductive dissolution of neutron- and gamma-irradiated magnetite

Afonso, Marı́a dos Santos; Risio, Cecilia Di; Roitberg, Adrián E.; Marqués, R. O.; Blesa, Miguel A.

doi:10.1016/1359-0197(90)90033-e

Cited by 6 publications

(4 citation statements)

References 6 publications

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“…A number of recent studies have observed enhanced radiation decomposition of water when associated with various solid oxides. − Iron oxides have a number of interesting biological and geological applications; a number of papers have examined radiation effects on stainless steel, , carbon steel, − magnetite, and pure iron ,− under a variety of atmospheres, but radiation effects on the molecular level at iron oxide surfaces are not completely understood. Currently, stainless steel containers are being proposed for long-term radioactive waste storage .…”

Section: Introductionmentioning

confidence: 99%

Radiation-Induced Chemical Changes to Iron Oxides

Reiff

LaVerne

2015

J. Phys. Chem. B

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The radiolysis of a variety of iron oxide powders with different amounts of associated water has been performed using γ rays and 5 MeV (4)He ions. Adsorbed water was characterized by both temperature-programmed desorption and diffuse reflection infrared Fourier transform spectroscopy to reveal a variety of active sites on the surface. Molecular hydrogen production was found only from water adsorbed on Fe2O3, and the yield was several orders of magnitude greater than that of bulk water. Aqueous slurries of FeO, Fe3O4, and Fe2O3 examined as a function of water fraction gave different yields of H2 depending on the oxide type and the amount of water. Examination of the iron oxide powders following irradiation by X-ray diffraction showed no change in crystal structure. Raman spectroscopy of the oxides revealed the formation of islands of Fe2O3 on the surfaces of FeO and Fe3O4. X-ray photoelectron spectroscopy of the oxides revealed the general formation of oxygen species following radiolysis.

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Section: Introductionmentioning

confidence: 99%

Radiation-Induced Chemical Changes to Iron Oxides

Reiff

LaVerne

2015

J. Phys. Chem. B

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“…Although a contribution to this difference produced by the change in acid (H2S04 vs. HC1) cannot be totally ruled out, the most important factor is certainly the influence of the different preparative methods on the extent of defects associated to imperfect coordination polyhedra: Sidhu et al (26) heated magnetite at 220°C for 3 h whereas our samples were precipitated at 90°C and not subjected to further heat treatment. As shown previously (27), important changes in reactivity are caused by annealing of coordination polyhedra defects. Figure 3 shows the fraction of dissolved iron and chromium in an experiment with 2.5 M H2S04 in the presence of 0.1 M KBrO, at 65°C.…”

Section: Resultsmentioning

confidence: 87%

Acid and oxidative dissolution of coprecipitated iron–chromium oxides

Rodenas¹,

Morando²,

Blesa³

et al. 1993

Can. J. Chem.

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. Can. J. Chem. 71, 771 (1993).A mixed Fe,Cr oxide formed of maghemite and chromium hydrous oxide was prepared by oxidative precipitation at 90°C. Mineral acids dissolve the chromium phase very quickly, whereas iron dissolves slowly and independently; there is little mutual influence in the dissolution behaviour. Calcination of this oxide at 600°C yields a mixture of a-Fe,03 and Cr, ,Fe, ,03 that leaches iron slowly upon acid attack. The reactivity of the oxide towards H+ is largely determined by the degree of crosslinking of the Cr-containing phase. Oxidative attack (by KBrO,) increases the rate of dissolution of both Cr and Fe, against simple expectations that Fe dissolution rates might be reduced. This effect is of importance in chemical cleaning and decontamination of stainless steels. This influence of acidity and [BrO,-] are interpreted in terms of the formation of surface =Cr(III)-0-Br(V) species that evolve to produce Cr(VI),,. These surface complexes form more readily than analogous solution species, making surface Cr(II1) more readily oxidizable than aqueous (Cr(1II). [Traduit par la redaction]

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“…The rate is given by eq. [12]; from the data in Fig. 3, it is possible to calculate the rates at any given The sigmoidal trace at low [Br03-] is due to incomplete scavenging of e,,-by BrO,-(eq.…”

Section: Resultsmentioning

confidence: 99%

“…This effect is due to the increased rate of removal from the surface (eq. [12]). The rate of generation of =~r " according to eq.…”

Section: Resultsmentioning

confidence: 99%

Radiation-induced dissolution of chromium oxide in aqueous solutions

Rodenas¹,

Chocron²,

Morando³

et al. 1996

Can. J. Chem.

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Gamma irradiation of suspensions of a commercial sample of a-Cr,03 in the presence of KBrO, in the concentration range 0.1 5 [BrOq] 5 0.4 mol dm-,, at pH 4 and 25OC brings about oxidative dissolution. Release of Cr(V1) to the solution proceeds at a constant rate that increases with bromate concentration, even in conditions of quantitative e -scavenging. A " Y mechanism of reactions is proposed in which OH and BrO, radicals oxidize surface Cr(II1) to Cr(IV), and Ionic release is achieved by oxidation of surface Cr(1V) by bromate. The corresponding set of equations was solved by a rigid method for the integration of ordinary differential equations, using these two heterogeneous rate constants as adjustable parameters. The calculated profiles are in close agreement with the experimental data.Key words: chromium oxides, radiation-induced dissolution, oxidation dissolution.RCsumC : L'irradiation y d'un Cchantillon commercial d'a-Cr,03, en prCsence de KBrO,, i d e s concentrations de Br0,-allant de 0,l i0.4 mol dm-,, a un pH de 4 et a 25"C, provoque une dissolution oxydante. L'apparition de Cr(V1) dans la solution se produit i une vitesse constante qui augmente avec la concentration de bromate, meme dans des conditions de piCgeage quantitatif de eaq-. On propose un mCcanisme des rkactions dans lequel les radicaux OH et BrO, oxydent la surface du Cr(II1) en Cr(1V) qui est par la suite oxydC par le bromate pour provoquer une apparition de chrome ionique. L'ensemble correspondant des Cquations a CtC rCsolu par une rude mtthode pour I'inttgration des Cquations diffkrentielles ordinaires qui utilise ces deux constantes de vitesse hCtCrogknes comme paramktres ajustables. Les profils calculCs sont en bon accord avec les donnCes expCrimentales.

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Reductive dissolution of neutron- and gamma-irradiated magnetite

Cited by 6 publications

References 6 publications

Radiation-Induced Chemical Changes to Iron Oxides

Radiation-Induced Chemical Changes to Iron Oxides

Acid and oxidative dissolution of coprecipitated iron–chromium oxides

Radiation-induced dissolution of chromium oxide in aqueous solutions

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