Mathematics

Sweeny, Robert F.; Davis, Robert S.; Hendrix, Charles D.

doi:10.1021/ie50672a012

Cited by 5 publications

(4 citation statements)

References 1 publication

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“…It has recently been shown that chlorinated aliphatic compounds can be reduced by metallic iron ( − ). A reactive permeable barrier technology based upon using metallic iron as the source of electrons for reductive dechlorination has been proposed and successfully implemented for in situ groundwater remediation ( , ).…”

Section: Introductionmentioning

confidence: 99%

Reduction of Vinyl Chloride in Metallic Iron−Water Systems

Deng

Burris

Campbell

1999

Environ. Sci. Technol.

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Batch experiments examining the kinetics and mechanism of vinyl chloride (VC) reduction by metallic iron in aqueous systems were performed. The effects of various iron loadings, VC concentrations, pH conditions, temperatures, and Fe-(II)/Fe(III) chelating agents (1,10-phenanthroline, 2,2′-dipyridyl, and nitrilotriacetic acid) on reduction kinetics were examined. Ethylene was the major carbon-containing product of VC reduction under all conditions examined, indicating hydrogenolysis. The reaction was pseudo-firstorder with respect to aqueous VC concentration. The amount of VC adsorption on iron surfaces was estimated from the rapid initial loss of VC from solution, and the resultant sorption isotherm was linear over the concentration range examined. The first-order kinetics and the linear sorption for VC suggest that the portion of VC sorption to surface reactive sites relative to nonreactive sorption sites is constant, unlike the behavior observed for the higher chlorinated ethenes. The activation energy of the reaction was measured to be 41.6 ( 2.0 kJ/mol, sufficiently large to indicate that the chemical reaction at the surface, rather than aqueous phase diffusion to the surface, controls the overall rate of the reaction. Experiments with the chelating agents suggest that the effect of available Fe-(II) on VC reduction is not significant.

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Section: Introductionmentioning

confidence: 99%

Reduction of Vinyl Chloride in Metallic Iron−Water Systems

Deng

Burris

Campbell

1999

Environ. Sci. Technol.

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“…Specific surface area and pore size distribution determinations were done by employing a NOVA Quantachrome instrument using nitrogen Mullet-BET analysis and the BJH method. The density of zinc dust determined on the NOVA Quantachrome was 7.0 g/cm 3 . That is close to 7.14 g/cm 3 for zinc metal (39).…”

Section: Methodsmentioning

confidence: 99%

“…The density of zinc dust determined on the NOVA Quantachrome was 7.0 g/cm 3 . That is close to 7.14 g/cm 3 for zinc metal (39). Nitrogen single-point BET analysis was done for a number of samples on a Micrometrics flowsorb II 2300 instrument.…”

Section: Methodsmentioning

confidence: 99%

“…Chloroalkanes, includ ing chloroform and carbon tetrachloride, have a cumulative toxicity and are carcinogenic. Sweeny ( , ) followed by Senzaki and Kumagai ( , ) were the first to report an environmental application of zero-valent iron for removal of chlorinated compounds from water, and they formulated some preliminary ideas for aboveground treatment reactors. Further interest in the use of zero-valent metals can be attributed to Gillham and O'Hannesin ( , ), who proposed the use of permeable walls containing metallic iron as a reactant, and Reynolds with co-workers (), who reported on aliphatic halide transformation in the presence of several metals, including iron, galvanized metals, aluminum, and copper.…”

Section: Introductionmentioning

confidence: 99%

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Activated and Nonactivated Forms of Zinc Powder: Reactivity toward Chlorocarbons in Water and AFM Studies of Surface Morphologies

Boronina

Lagadic

Sergeev

et al. 1998

Environ. Sci. Technol.

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This work was carried out with the purpose of developing effective reagents for decontamination of groundwater contaminated with chlorocarbons. Zinc metal as a reducing agent for carbon tetrachloride (CT), chloroform (Chl), and methylene chloride (MC) in aqueous solution has been studied in some detail, especially regarding activated forms of the metal. Chlorocarbon concentrations were monitored at certain time intervals by gas chromatography/mass spectrometry (GC/MS) analysis of the headspace and water phase. Reaction mixture headspace was additionally studied by a GC/headspace analysis system to detect the formation of hydrocarbons. Chloroform, methylene chloride, methyl chloride, methane, and acetylene were found to be products from CT reduction. For methylene chloride reduction, traces of cis and trans-1,2-dichloroethene (DCE) were also found. Activated by cryo or mechanical treatment, metallic zinc caused an increase in CT dechlorination rate and conversion into methane. After the first 2.5 h, more than 20% of CT was converted into methane by cryochemically activated zinc in comparison to 1.2% by conventional zinc dust. Furthermore, CT reduction by activated zinc caused the formation of DCEs and TCE. Pathways are proposed to account for the observed methane/methylene chloride ratio and DCEs and TCE formation that include sequential reductive dechlorination through organometallic and carbonoid species on the Zn surface. Furthermore, it seems likely that some methane can be formed in “one metal contact”, since significant amounts are formed early in the reaction. In attempts to learn more about morphological changes in the zinc during its consumption, pore volume/pore radii were determined, and atomic force microscope images were obtained. Zinc corrosion takes place rapidly at edges/corners leading to the formation of cavities with wide openings, large volumes, and increased specific surface areas. Pyramidal zinc “pillars” are formed during the process.

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Development of Optimization Models for Carbon Bed Design

Dostal¹,

Harrington²,

Clark³

et al. 1966

Journal AWWA

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This article presents optimization models that incorporated technologic and economic considerations in order to determine a best preliminary design for the unit process of granular carbon adsorption. Only the case of continuous reactivation was considered. Under some seasonal demand patterns, it may be more economical to operate the furnace on an intermittent basis. Such a policy would require the inclusion of additional startup and shutdown costs, and probably higher maintenance costs. These are not conveniently considered in the linear programing formulations; but this aspect could be investigated in the case of no off‐line storage by a dynamic programing approach.

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Mathematics

Cited by 5 publications

References 1 publication

Reduction of Vinyl Chloride in Metallic Iron−Water Systems

Reduction of Vinyl Chloride in Metallic Iron−Water Systems

Activated and Nonactivated Forms of Zinc Powder: Reactivity toward Chlorocarbons in Water and AFM Studies of Surface Morphologies

Development of Optimization Models for Carbon Bed Design

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