Chemistry and Physics Faculty Articles

Title

Mixed Redox Catalytic Destruction of Chlorinated Solvents in Soils and Groundwater

Document Type

Article

Publication Date

10-2008

Publication Title

Annals of the New York Academy of Sciences

Keywords

Mixed redox conditions, Mixed redox catalysis, Catalytic destruction, Chlorinated solvents, PCE conversion, Reduction, Oxidation

ISSN

0077-8923

Volume

1140

First Page

435

Last Page

445

Abstract

A new thermocatalytic method to destroy chlorinated solvents has been developed in the laboratory and tested in a pilot field study. The method employs a conventional Pt/Rh catalyst on a ceramic honeycomb. Reactions proceed at moderate temperatures in the simultaneous presence of oxygen and a reductant (mixed redox conditions) to minimize catalyst deactivation. In the laboratory, stable operation with high conversions (above 90% at residence times shorter than 1 s) for perchloroethylene (PCE) is achieved using hydrogen as the reductant. A molar ratio of H2/O2= 2 yields maximum conversions; the temperature required to produce maximum conversions is sensitive to influent PCE concentration. When a homologous series of aliphatic alkanes is used to replace hydrogen as the reductant, the resultant mixed redox conditions also produce high PCE conversions. It appears that the dissociation energy of the C–H bond in the respective alkane molecule is a strong determinant of the activation energy, and therefore the reaction rate, for PCE conversion. This new method was employed in a pilot field study in Tucson, Arizona. The mixed redox system was operated semicontinuously for 240 days with no degradation of catalyst performance and complete destruction of PCE and trichloroethylene in a soil vapor extraction gas stream. Use of propane as the reductant significantly reduced operating costs. Mixed redox destruction of chlorinated solvents provides a potentially viable alternative to current soil and groundwater remediation technologies.

Comments

©2008 New York Academy of Sciences

Additional Comments

NIH grant #: P42 ES04940

DOI

10.1196/annals.1454.044

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Peer Reviewed

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