Science Inventory

Degradation Kinetics of Carbon Tetrachloride by Sulfate Green Rust as Influenced by pH and Copper Ions

Citation:

Toews, B. K. AND C. SU. Degradation Kinetics of Carbon Tetrachloride by Sulfate Green Rust as Influenced by pH and Copper Ions. Presented at Research Day at Northeastern State University, Broken Arrow, OK, November 14, 2008.

Impact/Purpose:

Because green rusts play an important role in both active remediation and natural attenuation of contaminants in the subsurface, it is necessary to study their interactions with chlorinated solvents.

Description:

Chlorinated solvents such as trichloroethene (TCE, C2HCl3) and carbon tetrachloride (CT, CCl4) are priority groundwater contaminants at many EPA field sites. Green rust (GR) minerals are important corrosion products of zerovalent iron (Fe0) that has been used in permeable reactive barrier (PRB) technologies to remediate groundwater contaminants. Green rusts also occur naturally and are found in certain soils and sediments. Because green rusts play an important role in both active remediation and natural attenuation of contaminants in the subsurface, it is necessary to study their interactions with chlorinated solvents. Previous studies in our laboratory have examined interactions between TCE and sulfate green rust (SGR) and little TCE degradation was found. In addition, although preliminary evidence suggests that SGR can degrade CT, little is known about the influence of geochemical factors such as pH and transition metals like copper (as a catalyst) on reaction kinetics. Therefore, the purpose of this project was to study degradation kinetics and products of CT by iron(II, III)hydroxysulfate green rust (sulfate green rust, Fe(II)4Fe(III)2(OH)12SO4•3H2O) as a function of reaction time (0 to 360 hours), pH (6 to 11), and concentrations of copper (Cu(II)) ions (0 to 10 mM) in microcosm tests. Results indicate that the pseudo-first-order reaction equation is able to satisfactorily describe most of the data. Degradation rates generally increased with an increase in pH while the addition of copper resulted in faster and more complete CT degradation. These results suggest that in PRB systems where pH is high (8-11), CT may readily degrade.

URLs/Downloads:

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Record Details:

Record Type: DOCUMENT (PRESENTATION/POSTER)
Product Published Date: 11/14/2008
Record Last Revised: 06/29/2010
OMB Category: Other
Record ID: 202177

Organization:

U.S. ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF RESEARCH AND DEVELOPMENT

NATIONAL RISK MANAGEMENT RESEARCH LABORATORY

GROUND WATER AND ECOSYSTEMS RESTORATION DIVISION

SUBSURFACE REMEDIATION BRANCH