Chromium(III) hydrolysis constants and solubility of chromium(III) hydroxide

Rai, Dhanpat; Sass, Bruce; Moore, Dean A.

doi:10.1021/ic00250a002

Cited by 659 publications

(471 citation statements)

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“…Both mechanisms result in the formation of Cr III -Fe IIIhydroxides with a Cr-solubility far below critical limits (log[Cr 3+ ] < -7 at pH ) 7 (27)). The microanalytical findings (i.e., Cr-containing precipitates on the gravel surfaces and solids with a Cr/Fe ratio of 1/3 in the corrosion rinds) strongly suggest that, as intended in the design process, homogeneous Cr VI reduction is an important pathway within the zone impacted by ZVI corrosion.…”

Section: Resultsmentioning

confidence: 99%

Assessment of Long-Term Performance and Chromate Reduction Mechanisms in a Field Scale Permeable Reactive Barrier

Flury

Frommer

Eggenberger

et al. 2009

Environ. Sci. Technol.

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An innovative full-scale implementation of a permeable reactive barrier, consisting of a double-row of cylinders filled with zerovalent iron shavings, for chromate remediation was monitored over four years. Solid samples were analyzed to elucidate (i) the relevant corrosion mechanisms and products, (ii) the pathways of chromate reduction and immobilization, and (iii) the long-term performance of the barrier situated in a hydrological and geochemical complex groundwater regime. Sampling and analysis of groundwater and reactive material revealed an oxidative iron corrosion zone evolving in the inflow and a zone of anaerobic iron corrosion in the center and outflow of the barrier. Chromate reduction was mainly confined to the inflow region. The formation and thickness of corrosion rinds depended on sampling time, position, and depth, as well as on the size, shape, and graphite content. In the inflow, the corrosion rinds mostly consisted of goethite and ferrihydrite. X-ray absorption fine structure spectroscopy revealed two distinct Cr III species, most likely resulting from homogeneous and heterogeneous redox reaction pathways, respectively. The longevity and long-term effectiveness of the PRB appears to be primarily limited by reduced corrosion rates of the ZVI-shavings because of the thick layers of Fe-hydroxides.

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Section: Resultsmentioning

confidence: 99%

Assessment of Long-Term Performance and Chromate Reduction Mechanisms in a Field Scale Permeable Reactive Barrier

Flury

Frommer

Eggenberger

et al. 2009

Environ. Sci. Technol.

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“…However, it has been above 10 1 M concentration [34,35]. In solution, Cr (III) reported that M6ssbauer spectroscopy cannot be applied to exists as the cations /Cr 3 +(aq) and hydroxo complexes Cr because of the lack of suitable Cr isotopes for Cr,,,(OH)(nl-n)+ [34]. However, /Cr 3 + (aq) and Cr(OH) (3-") measurement [58].…”

Section: Introductionmentioning

confidence: 96%

“…Only under very acidic (pH < 5) or very transition metals) [55], Auger electron spectroscopy (AES) basic (14 <pH) conditions will Cr(III) exhibit solubility [56], and M6ssbauer spectroscopy [57]. However, it has been above 10 1 M concentration [34,35]. In solution, Cr (III) reported that M6ssbauer spectroscopy cannot be applied to exists as the cations /Cr 3 +(aq) and hydroxo complexes Cr because of the lack of suitable Cr isotopes for Cr,,,(OH)(nl-n)+ [34].…”

Section: Introductionmentioning

confidence: 99%

Determination of chromium valence over the range Cr(0)–Cr(VI) by electron energy loss spectroscopy

2006

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“…It was generally accepted that anionic monomers, Cr(OH) j (j-3)-(j = 4, 5 or 6), form in alkaline solutions and become dominant when pH is above 12. 2,16 However, this assumption was solely based on the fitting of solubility data and the species have not been identified. In fact, recent studies 17 have cast doubt on the formation of Cr(OH) 4 -and the speciation of chromium(III) in alkaline solutions still remains uncertain.…”

Section: Introductionmentioning

confidence: 99%

Oligomerization of chromium(iii) and its impact on the oxidation of chromium(iii) by hydrogen peroxide in alkaline solutions

Rao

Zhang

Friese

et al. 2002

J. Chem. Soc., Dalton Trans.

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Kinetic studies on the oxidation of separated/characterized chromium(III) oligomers by hydrogen peroxide indicate that the degree of oligomerization has a significant impact on the rate of oxidation in alkaline solutions. The oxidation rate constant decreases in the order: monomer > dimer > trimer > aged/unseparated chromium(III) solution where higher oligomers dominate. SummaryMonomeric, dimeric and trimeric chromium(III) species in solution were separated by ion exchange and characterized with UV/Vis absorption and Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS). The kinetics of the oxidation of the separated species by hydrogen peroxide in alkaline solutions was studied by conventional and stopped-flow UV/Vis absorption spectroscopy. Results indicate that the intensity of Cr-Cr scattering in the EXAFS spectra (d Cr-Cr ~ 2.99 Å), a measure of the degree of oligomerization, increases as the solution alkalinity is increased. As the oligomerization proceeds, the rate of oxidation by hydrogen peroxide in alkaline solutions decreases in the order: monomer > dimer > trimer > aged/unseparated alkaline chromium(III) solution where higher 1 oligomers dominate. The dominant redox pathway has an inverse order with respect to C NaOH . The data suggest that the rate-determining step involves the weakening of the bridging bonds in the oligomer and a concomitant release of one hydroxyl group from the chromium(III) moiety upon the attack by hydrogen peroxide.

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Chromium(III) hydrolysis constants and solubility of chromium(III) hydroxide

Cited by 659 publications

References 0 publications

Assessment of Long-Term Performance and Chromate Reduction Mechanisms in a Field Scale Permeable Reactive Barrier

Assessment of Long-Term Performance and Chromate Reduction Mechanisms in a Field Scale Permeable Reactive Barrier

Determination of chromium valence over the range Cr(0)–Cr(VI) by electron energy loss spectroscopy

Oligomerization of chromium(iii) and its impact on the oxidation of chromium(iii) by hydrogen peroxide in alkaline solutions

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