Kinetics of Chromate Reduction by Ferrous Iron

Fendorf, S. E.; Li, Guangchao

doi:10.1021/es950618m

Cited by 362 publications

(198 citation statements)

References 19 publications

Supporting

Mentioning

192

Contrasting

Unclassified

Order By: Relevance

“…However, ferrous iron from the Fe III /Fe II redox couple, either in aqueous solution or adsorbed on mineral surfaces, can act as a reductant for organic and inorganic soil components (e.g. MnO 2 ) [77][78][79] and contaminants [80,81]. Furthermore, it has been shown that adsorbed or structural Table 1).…”

Section: Implications For Fe 0 Reactive Wallsmentioning

confidence: 99%

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

Noubactep¹

2008

Environmental Technology

344

308

View full text Add to dashboard Cite

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.

show abstract

Section: Implications For Fe 0 Reactive Wallsmentioning

confidence: 99%

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

Noubactep¹

2008

Environmental Technology

344

308

View full text Add to dashboard Cite

show abstract

“…on bentonite is an exothermic process. is exothermic effect can be explained by the forces of interaction between the bentonite and metal, which are stronger than those existing in both bentonite and metal alone, which means that it would prefer the product than reactant [30]. e almost zero values of Δ * suggests that the entropy of the system is decreased or stayed constant.…”

Section: Ermodynamics Of Sorption Onmentioning

confidence: 99%

Sorption of Uranium(VI) and Thorium(IV) by Jordanian Bentonite

Khalili

Salameh

Shaybe

2012

Journal of Chemistry

View full text Add to dashboard Cite

Puri�cation of raw bentonite was done to remove quartz. is includes mixing the raw bentonite with water and then centrifuge it at �50 rpm; this process is repeated until white puri�ed bentonite is obtained. �RD, �RF, FTIR, and SEM techniques will be used for the characterization of puri�ed bentonite. e sorption behavior of puri�ed Jordanian bentonite towards UO 2 2+and  4+ metal ions in aqueous solutions was studied by batch experiment as a function of pH, contact time, temperature, and column techniques at 25.0 ∘ C and pH = 3. e highest rate of metal ions uptake was observed aer 18 h of shaking, and the uptake has increased with increasing pH and reached a maximum at pH = 3. Bentonite has shown high metal ion uptake capacity toward uranium(VI) than thorium(IV). Sorption data were evaluated according to the pseudo-second-order reaction kinetic. Sorption isotherms were studied at temperatures 25.0 ∘ C, 35.0 ∘ C, and 45.0 ∘ C. e Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) sorption models equations were applied and the proper constants were derived. It was found that the sorption process is enthalpy driven for uranium(VI) and thorium(IV). Recovery of uranium(VI) and thorium(IV) ions aer sorption was carried out by treatment of the loaded bentonite with different concentrations of HNO 3 1.0 M, 0.5 M, 0.1 M, and 0.01 M. e best percent recovery for uranium(VI) and thorium(IV) was obtained when 1.0 M HNO 3 was used.

show abstract

“…[4,14,22] However, ferrous iron from the Fe 2+ -Fe 3+ redox couple, either in aqueous solution or adsorbed on mineral surfaces, can be part of a convenient delivery path for electrons, reducing and immobilizing organic and inorganic pollutants. [23][24][25][26][27] Furthermore, pollutant coprecipitation with corrosion products has been demonstrated as another removal pathway. [28,29] Therefore there are at least three possible immobilization pathways for several pollutants: reduction by Fe°, by Fe 2+ and coprecipitation with corrosion products.…”

Section: Some Relevant Aspects Of the "Pollutant-zvi-h 2 O"-systemmentioning

confidence: 99%

Investigating the Mechanism of Uranium Removal by Zerovalent Iron

Noubactep¹,

Meinrath

Merkel

2005

Environ. Chem.

View full text Add to dashboard Cite

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.

show abstract

Kinetics of Chromate Reduction by Ferrous Iron

Cited by 362 publications

References 19 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

Sorption of Uranium(VI) and Thorium(IV) by Jordanian Bentonite

Investigating the Mechanism of Uranium Removal by Zerovalent Iron

Contact Info

Product

Resources

About

Kinetics of Chromate Reduction by Ferrous Iron

Cited by 362 publications

References 19 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

Sorption of Uranium(VI) and Thorium(IV) by Jordanian Bentonite

Investigating the Mechanism of Uranium Removal by Zerovalent Iron

Contact Info

Product

Resources

About

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