Deuterium Exchange between Water and Boehmite (α-Alumina, Monohydrate).

Wei, Yung-Kang; Bernstein, R. B.

doi:10.1021/j150575a023

Cited by 22 publications

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A similar slow movement of protons either into or out of goethite was observed in this work and for soil particles by Mora & Barrow (1996). A diffusion mechanism has also been postulated for the reaction of deuterium with an aluminium oxide (Wei & Bernstein, 1959) and for the reaction of protons with an iron oxide (Bérubé et al , 1967). An analogous migration into micropores, boundary layers of domains or defects in the goethite structure has been postulated by Brümmer et al (1988), Fischer et al (1996), Strauss et al (1997b), Gerth (2005) and Mikutta et al (2006) to explain the slow reactions of cations and anions with goethite, while Axe & Trivedi (2002) call this process an intraparticle surface diffusion into microporous sorbents.…”

Section: Discussionsupporting

confidence: 81%

Observations and modelling of the reactions of 10 metals with goethite: adsorption and diffusion processes

Fischer

Brümmer

Barrow

2007

European J Soil Science

View full text Add to dashboard Cite

A sample of goethite was mixed for periods which ranged from 2 hours to 8 weeks with solutions of dilute nitrate salts of Pb, Hg, Cd, Zn, Cu, Ni, Co, Mn, Cr and Al. The amount of sorption after each period was measured for an appropriate pH range for each metal. The sorption behaviour was characterized both by using characteristics of the sorption curves such as the pH at which half of the added metal was sorbed (pH 50 ) and by fitting a model in which sorption was mainly characterized by an affinity constant and by a diffusion constant. Initial sorption, whether characterized by the pH 50 or by the affinity constant, was closely correlated with the appropriate dissociation constants of the metals. The greater the affinity of the metals for hydroxide ions, the greater their affinity for the goethite surface. The metals differed in the rate at which they continued to react with the goethite. Lead had the slowest continuing reaction, cobalt the fastest. The continuing reaction was due to diffusion into the particles. It was characterized by the fitted diffusion constant and by the change with time in the pH 50 . For seven of the eight divalent metals, these were correlated with the ionic radius of the metals: the larger the radius, the slower the reaction. For Al and Cr, rates were slower than would be expected from the ionic radii and we suggest this shows that these ions react as the larger M(OH) 2þ ions. The behaviour of Ni was consistent with oxidation of the surface species and diffusion of Ni(OH) 2þ ions. The continuing reaction was similar to that observed when metal ions react with soils and suggests that their reaction with iron oxides is important in soils. The results also show that studies in which sorption is measured at only one period of reaction are incomplete and the application of equilibrium models to such results is misleading.

show abstract

Section: Discussionsupporting

confidence: 81%

Observations and modelling of the reactions of 10 metals with goethite: adsorption and diffusion processes

Fischer

Brümmer

Barrow

2007

European J Soil Science

View full text Add to dashboard Cite

show abstract

“…The magnitude of zlE is comparable to activation energies reported in some other instances of what is thought to be proton diffusion in oxides, e.g., 3.2 kcal/ mole in MnO2 (9), 13 kcal/mole in cc-A120~. H20 (10), and 4.5 kcal/mole in ice (10). For metal ions in oxides, AE has been found to be roughly an order of magnitude higher, and it is generally higher still for oxide ions, so that this value of AE is consistent with the proposed mechanism involving the diffusion of protons.…”

Section: Resultssupporting

confidence: 79%

“…H20 (10), and 4.5 kcal/mole in ice (10). For metal ions in oxides, AE has been found to be roughly an order of magnitude higher, and it is generally higher still for oxide ions, so that this value of AE is consistent with the proposed mechanism involving the diffusion of protons.…”

Section: E = Eo" Jr 2303 (Rt/f) Log T'/ --(T --T) /2 --1mentioning

confidence: 57%

Discharge Mechanism of the V[sub 2]O[sub 5] Electrode

Newby¹,

Scott²

1970

J. Electrochem. Soc.

View full text Add to dashboard Cite

The behavior of V205 single crystals, grown from the melt, during cathodic polarization and recovery, has been investigated. The dependence of potential on pH showed that the only plausible reduction product was a solid oxide or oxyhydroxide, polarization being due to the formation of a solid solution. In the pH range 2.0-5.5, the curve of electrode potential vs. time during both polarization and recovery was accurately predicted by an equation, already applied to MnO2, derived from the assumption that the product is removed from the surface by diffusion into the electrode. Using tritium as a tracer, it was shown that hydrogen is incorporated in the electrode during discharge at pH 4.7. The activation energy for diffusion was found to be 6.7 kcal/mole, which is consistent with bipolar diffusion of protons and electrons.Vanadium pentoxide as a cathode in electrochemical cells has previously been studied to a limited extent. Watson and Scott (1) studied polycrystalline V20~ electrodes in an acid electrolyte saturated with dissolved V205. They found that, for low constant-current discharges, polarization curves for this electrode were qualitatively similar to those for MnO2 in an alkaline medium. These authors were partially successful in applying a theory developed (2) for MnO2 to these discharge curves. This theory is based on the assumption that polarization is caused by an accumulation of reduced product in solid solution on the electrode surface and that recovery is a result of the subsequent diffusion of the product into the electrode. Its application to MnO2 has been demonstrated quantitatively (3).Shukler and Kuz'min (4) studied the cathodic behavior of pressed pellet electrodes made of 80% V205 and 20% graphite. These authors used H2SO4 as an electrolyte and worked at higher apparent current densities than Watson and Scott. They concluded that the V205 electrode is reduced directly to a second solid phase on the electrode surface. This phase was identified as one containing V(IV).Here we attempt to determine the discharge mechanism for single crystalline V205 in NH4C1 buffered solutions and to show under what experimental conditions the theory applicable to MnO2 can be expected to predict the discharge and recovery curves. ExperimentalElectrode preparation.--Single crystals of V205 were grown using a modification of a method originally due to Arsen'eva and Kurchatov (5) and supplied to this laboratory by Boros in a private communication.The crystals were grown in a platinum crucible in an air atmosphere. Baker analyzed (99.5%) V20~ was melted at 690~ and a small seed of crystalline V205 was placed on the melt surface. The temperature was then slowly raised until only a single crystallite remained. At this point the melt was cooled at a rate of approximately 1~ min for a total of 10~176 The single crystal grew as a thin, flat sheet on the surface of the melt with the ac crystallographic plane parallel to the surface of the melt. The crystal was removed before it reached the edge of the crucible by lifting it...

show abstract

“…Therefore, a rough estimate of the activation energy value for proton diffusion in α‐FeOOH can be made ~0.45 eV. This estimate concurs with the values reported for other materials 0.41 eV (SrTiO 3 ) and 0.42 (CaTiO 3 ), 0.61 eV (Ca(OH) 2 ), and 0.56 eV (α‐AlO(OH)). Furthermore, this study suggests that micro‐Raman spectroscopy can be extended further and utilized for real‐time studies of the proton diffusion activation energy via dehydration processes when possible.…”

Section: Resultsmentioning

confidence: 99%

In‐situ isothermal micro‐Raman spectroscopy reveals the activation energy of dehydration in α‐FeOOH

Sendova

Hosterman

Grebe

2017

J Raman Spectroscopy

View full text Add to dashboard Cite

A real‐time, isothermal micro‐Raman spectroscopy was developed as a single technique for monitoring the solid state kinetics of dehydration and measuring its activation energy. The technique comprises of acquisition and numerical analysis of a set of isothermal time‐dependent Raman spectra. α‐FeOOH transformation to Fe2O3 in N2 atmosphere was continuously monitored for up to 16 h at three temperatures. Dehydration activation energy of 1.4(1) eV was estimated. The Raman band evolution of two modes with different symmetries (B1g ~ 240 cm−1 and Ag ~ 400 cm−1) and the intensity decay of B1g mode at ~540 cm−1 are analyzed independently utilizing kinetic model‐free approach. The study opens new possibilities for developing versatile solid state chemical and bio‐chemical Raman sensors and advances the field of analytical micro‐Raman spectroscopy. Copyright © 2017 John Wiley & Sons, Ltd.

show abstract

Deuterium Exchange between Water and Boehmite (α-Alumina, Monohydrate).

Cited by 22 publications

References 0 publications

Observations and modelling of the reactions of 10 metals with goethite: adsorption and diffusion processes

Observations and modelling of the reactions of 10 metals with goethite: adsorption and diffusion processes

Discharge Mechanism of the V[sub 2]O[sub 5] Electrode

In‐situ isothermal micro‐Raman spectroscopy reveals the activation energy of dehydration in α‐FeOOH

Contact Info

Product

Resources

About