Degradation of carbon tetrachloride by iron metal: Complexation effects on the oxide surface

Johnson, T. W.; Fish, William; Gorby, Yuri A.; Tratnyek, Paul G.

doi:10.1016/s0169-7722(97)00063-6

Cited by 191 publications

(137 citation statements)

References 56 publications

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“…stirring with 0 r/min). On the other hand, mixing may be disadvantageous because in nature (and in column experiments) formed corrosion products remain mostly on the Fe 0 surface and limit the surface accessibility for contaminants [35,[67][68][69][70]. It is the objective of this study to discuss the effect of the film of corrosion products on the accessibility of the Fe 0 surface.…”

Section: Implications For Fe 0 Reactive Wallsmentioning

confidence: 99%

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A CRITICAL REVIEW ON THE PROCESS OF CONTAMINANT REMOVAL IN FE⁰–H₂O SYSTEMS

Noubactep¹

2008

Environmental Technology

344

308

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A central aspect of the contaminant removal by elemental iron materials (Fe 0 or Fe 0 materials) is that reduction reactions are mediated by the iron surface (direct reduction). This premise was introduced by the pioneers of the reactive wall technology and is widely accepted by the scientific community. In the meantime enough evidence has been provided to suggest that contaminant reduction through primary corrosion products (secondary reductants) does indeed occur (indirect reduction). It was shown for decades that iron corrosion in the pH range of natural waters (4-9) inevitably yields an obstructive oxide film of corrosion products at the metal surface (oxide film). Therefore, contaminant adsorption on to corrosion products and contaminant co-precipitation with corrosion products inevitably occurs. For adsorbed and coprecipitated contaminants to be directly reduced the oxide film should be electronic conductive. This study argues through a literature review a series of points which ultimately lead to the conclusion that, if any quantitative contaminant reduction occurs in the presence of Fe 0 materials, it takes place within the matrix of corrosion products and is not necessarily a direct reduction. It is concluded that Fe 0 materials act both as source of corrosion products for contaminant adsorption/coprecipitation and as a generator of Fe II and H 2 (H) for possible catalytic contaminant reduction.

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Section: Implications For Fe 0 Reactive Wallsmentioning

confidence: 99%

“…It should be acknowledged that several studies have investigated the role of iron corrosion products on the process of contaminant removal in Fe 0 -H 2 O systems [35][36][37][38][39][40]. However, the objective of the investigators was mostly to explain the role of the film in mediating direct contaminant reduction in Fe 0 -H 2 O systems.…”

Section: Introductionmentioning

confidence: 99%

A CRITICAL REVIEW ON THE PROCESS OF CONTAMINANT REMOVAL IN FE⁰–H₂O SYSTEMS

Noubactep¹

2008

Environmental Technology

344

308

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“…[Gu et al 2002, Matheson et al 2002 The efficiency of ZVI for contaminant removal is presumed to highly depend on the properties of the metal surface because contaminant reduction reaction may mainly occur on the surface of iron [Keum & Li 2005, Matheson & Tratnyek 1994, Weber 1996 . Although it has been recognised that the formation of iron oxide or hydroxide over the surface may decrease the reactivity of ZVI materials, available information of the effects of oxide-films on the reductive capacity of ZVI materials results largely from well-mixed batch experiments [Huang et al 2003, Johnson et al 1998, Kim & Carraway 2000, Lin & Lo 2005, Ritter et al 2002, Weber et al 1996 . However, this experimental procedure (shaken or stirred batch experiments) may be inconsistent with groundwater environments (flow velocities 5-50 cm/day) where iron precipitates are continuously generated on ZVI surface, probably forming a reactive physical barrier to several contaminants [Devlin et al 1998, Devlin & Allin 2005, Mishra & Farrell 2005, Noubactep et al 2001 .…”

Section: Introductionmentioning

confidence: 99%

Investigating the Mechanism of Uranium Removal by Zerovalent Iron

Noubactep¹,

Meinrath

Merkel

2005

Environ. Chem.

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Environmental ContextGroundwater remediation is mostly a costly long-term process. In-situ remediation by permeable reactive barriers is a potential solution. For pollution by halogenated hydrocarbons, nitrate, and chromium, zerovalent iron (ZVI) has been found to induce a chemical reduction.ZVI remediation technology has been extended to metal pollution, where one of the major removal mechanisms seems to be co-precipitation with the products of iron corrosion. Due to difficulties of identifying reaction products in the matrix of corrosion products, investigation methods for characterising the contaminant removal with respect to interactions between contaminant and corrosion products need to be developed. AbstractZerovalent iron (ZVI) has been proposed as a reactive material in permeable in-situ walls for groundwater contaminated by metal pollutants. For such pollutants which interact with corrosion products, the determination of the actual mechanism of their removal is very important to predict the long-term stability of reactive walls. From a study of the effects of pyrite (FeS 2 ) and manganese nodules (MnO 2 ) on the uranium removal potential of a selected ZVI material, a test methodology (FeS 2 -MnO 2 -method) is suggested to follow the pathway of contaminant removal by ZVI materials. An interpretation of the removal potential of ZVI for uranium in presence of both additives corroborates coprecipitation with iron corrosion products as a major removal mechanism for uranium.

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“…Zero-valent metals have been the focus of much recent attention in the environmental 27 community because they offer great promise in treating contaminated groundwater through their 28 ability to promote abiotic reductive dehalogenation (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Nevertheless, many basic questions 29 about the mechanism of these reactions remain unanswered.…”

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confidence: 99%

Alkyl Bromides as Mechanistic Probes of Reductive Dehalogenation: Reactions of Vicinal Dibromide Stereoisomers with Zerovalent Metals

Totten

Jans

Roberts

2001

Environ. Sci. Technol.

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Whether reductive dehalogenation proceeds via a one-or a two-electron mechanism has been suggested to affect product distributions, hence potentially influencing the success of engineered treatment systems. In this work, we explore vicinal dibromide stereoisomers as "probes" of the concertedness of electron transfer in reduction by aqueous suspensions of iron and zinc metal. Dibromides consisted of 2,3-dibromopentane (diBP) stereoisomers and (()-1,2-dibromo-1,2-diphenylethane. All dibromides reacted with metals to give the same E:Z ratio of olefins observed during dehalogenation by iodide (a two-electron reductant). Reduction by Cr(II) (a one-electron reductant) yielded distinctly different proportions of E and Z olefins. Although this might be construed as evidence that metals function as two-electron reductants, high stereospecificity was also obtained for reduction of diBPs by Fe(II) adsorbed to goethite, a presumed one-electron reductant; this can be explained by two single-electron transfers in rapid succession, facilitated by the locally elevated concentration of reducing equivalents at the oxide-water interface. The results suggest that reduction of alkyl halides by metals is not likely to produce free radicals that persist long enough to undergo radical-radical coupling or hydrogen-atom abstraction from minor dissolved constituents. Apparent free-radical coupling products are more likely to result from (possibly surface-bound) organometallic intermediates.

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Degradation of carbon tetrachloride by iron metal: Complexation effects on the oxide surface

Cited by 191 publications

References 56 publications

A CRITICAL REVIEW ON THE PROCESS OF CONTAMINANT REMOVAL IN FE⁰–H₂O SYSTEMS

A CRITICAL REVIEW ON THE PROCESS OF CONTAMINANT REMOVAL IN FE⁰–H₂O SYSTEMS

Investigating the Mechanism of Uranium Removal by Zerovalent Iron

Alkyl Bromides as Mechanistic Probes of Reductive Dehalogenation: Reactions of Vicinal Dibromide Stereoisomers with Zerovalent Metals

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Degradation of carbon tetrachloride by iron metal: Complexation effects on the oxide surface

Cited by 191 publications

References 56 publications

A CRITICAL REVIEW ON THE PROCESS OF CONTAMINANT REMOVAL IN FE0–H2O SYSTEMS

A CRITICAL REVIEW ON THE PROCESS OF CONTAMINANT REMOVAL IN FE0–H2O SYSTEMS

Investigating the Mechanism of Uranium Removal by Zerovalent Iron

Alkyl Bromides as Mechanistic Probes of Reductive Dehalogenation: Reactions of Vicinal Dibromide Stereoisomers with Zerovalent Metals

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A CRITICAL REVIEW ON THE PROCESS OF CONTAMINANT REMOVAL IN FE⁰–H₂O SYSTEMS

A CRITICAL REVIEW ON THE PROCESS OF CONTAMINANT REMOVAL IN FE⁰–H₂O SYSTEMS