The Role of Oxides in Reduction Reactions at the Metal-Water Interface

Scherer, Michelle M.; Balko, Barbara A.; Tratnyek, Paul G.

doi:10.1021/bk-1998-0715.ch015

Cited by 129 publications

(141 citation statements)

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“…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

343

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: Introductionmentioning

confidence: 99%

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

Noubactep¹

2008

Environmental Technology

343

308

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“…With the addition of chloride, the decrease in reactivity could be slowed due to pitting in the oxide layer on the outside of the metal. Pitting in the oxide layer occurs when a strong anion enhances the dissolution of the oxide at a small defect in the film (Scherer et al, 1999). The oxide layer is dissolved until it is breached and bare metal is uncovered (Scherer et al, 1999).…”

Section: Chapter II Literature Reviewmentioning

confidence: 99%

“…Pitting in the oxide layer occurs when a strong anion enhances the dissolution of the oxide at a small defect in the film (Scherer et al, 1999). The oxide layer is dissolved until it is breached and bare metal is uncovered (Scherer et al, 1999). At this point a pH gradient is produced due to the hydrolysis of Fe 2+ at the bottom of the pit, this produces an acidic environment and the dissolution of oxide layer at the surface produces a basic environment (Scherer et al, 1999).…”

Section: Chapter II Literature Reviewmentioning

confidence: 99%

Single-step treatment of 2,4-dinitrotoluene via zero-valent metal reduction and chemical oxidation

Thomas

Hernández

Kuo

2008

Journal of Hazardous Materials

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Many nitroaromatic compounds (NACs) are considered toxic and potential carcinogens. The purpose of this study was to develop an integrated reductive/oxidative process for treating NAC contaminated waters. The process consists of the combination of zero-valent manganese or iron and a hydroxyl radical based treatment technique.Corrosion promoters were added to the contaminated water to minimize passivation of the metallic species. Water contaminated with 2,4-dinitrotoluen (DNT) was treated with the integrated process using a recirculating batch reactor. It was demonstrated that addition of corrosion promoters to the contaminated water enhanced the rate of reaction of 2,4-DNT with zero-valent iron or manganese. Results showed that iron provided greater reduction of 2,4-DNT than manganese. Chemical oxidation was used to mineralize the reduction products. The degree of mineralization was measured analyzing the samples for total organic carbon and nitrates. A proposed reaction and corrosion mechanisms and rate expressions were developed during the course of the study.ii DEDICATION This thesis is dedicated to the memory of my late grandmother, Emily Thomas.Her amazing will and determination was seconded only by the love she had for her family. You are missed Nanny, I love you. I would like to thank my colleagues,

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“…The reactivity of ZVI varies greatly as its surface becomes coated with secondary mineral coatings formed when ZVI is oxidized (Sass et al, 1998;Scherer et al, 1998;Johnson et al, 1998;. As the ZVI surfaces become increasingly covered with secondary precipitates the removal rates change.…”

Section: Zero-valent Iron Chemistrymentioning

confidence: 99%

“…Satapanajaru et al (2000) reported that although the reaction rates may initially decrease, they eventually increase again over extended durations. They attributed this chemical behavior to the semiconductor nature and the increased adsorptive capacity of the solid phase as magnetite and green rust are formed (Scherer et al, 1998). In the extraction trench design, it is believed that flow fluctuations due to weather events will help to physically remove loose iron oxyhydroxide particles from ZVI surfaces in the reaction cell and convey those particles to the settling/oxidation basin for long-term storage.…”

Section: Zero-valent Iron Chemistrymentioning

confidence: 99%