Overcoming Barriers to the Remediation of Carbon Tetrachloride Through Manipulation of Competing Reaction Mechanisms

PDF Version Also Available for Download.

Description

Quantify the kinetics of all competing product-formation pathways, over a range of conditions relevant to groundwater remediation, using well-mixed batch reactors and analysis primarily by chromatography. At OGI, batch experiments were conducted on Fe(0) systems (both Fisher Electrolytic and Nano-sized iron). The experiments were done with and without buffer. The buffered experiments tried to contrast two buffers: an organic buffer (EPPS, presumably a H atom donor), and the inorganic borate. In the buffered experiments, the pH was varied (7.3 and 8.4). For the pre-exposure treatment, after trying a variety of methods, like shaking and not shaking for varied amounts of ... continued below

Physical Description

vp.

Creation Information

Tratnyek, Paul G. June 1, 2003.

Context

This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this report can be viewed below.

Who

People and organizations associated with either the creation of this report or its content.

Sponsor

Publisher

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this report. Follow the links below to find similar items on the Digital Library.

Description

Quantify the kinetics of all competing product-formation pathways, over a range of conditions relevant to groundwater remediation, using well-mixed batch reactors and analysis primarily by chromatography. At OGI, batch experiments were conducted on Fe(0) systems (both Fisher Electrolytic and Nano-sized iron). The experiments were done with and without buffer. The buffered experiments tried to contrast two buffers: an organic buffer (EPPS, presumably a H atom donor), and the inorganic borate. In the buffered experiments, the pH was varied (7.3 and 8.4). For the pre-exposure treatment, after trying a variety of methods, like shaking and not shaking for varied amounts of time, it was decided to stick with not shaking and have a pre-exposure of 24 hours. The unbuffered data did not show any marked trend with increasing mass of Felc. However, 3.5 g of Fe showed about 100% conversion to CHCl3, and 1g of Fe showed 50% conversion. At pHs 8.4 and 7.3, there was no trend observed for branching ratios between EPPS and Borate buffer. kCT (disappearance rate constant of carbon tetrachloride) values were found to be different from CT and CF fits. Experiments with nano-iron (unbuffered, buffered with both buffers at pH 8.3), did not show any trend with respect to Fisher Iron, except for the unbuffered experiments, where the CF ''yield'' was less in the nano iron case. Future experiments involve testing for chloride, formate and CO, and performing experiments over a wider range of pH and buffers. Batch experiments were conducted at PNNL to compare the efficiency and product distribution of representative Fe(II) and Fe(0) systems applied to dechlorination of CCl4. These experiments involved (1) a smectite clay with Fe(III) in its structure that had been reduced to Fe(II) by dithionite treatment, (2) the same clay to which Fe(II) was added as an exchangeable cation, (3) electrolytic Fe(0) from Fisher, and (4) a mixture of the reduced clay and Fe(0). Experiments were conducted in headspace vials at pH 7 in either bicarbonate or bis-tris propane buffers. Reactant and product concentrations were determined by headspace analysis using GC/MS. Results from the first run of this experiment showed relatively little dechlorination by the Fe(II) system, and from 50-80% dechlorination by the Fe(0) system after 48 h. Essentially no CHCl3 was seen in the Fe(II) system, whereas as 30% of the original CCl4 was converted to CHCl3 in the Fe(0) system. Very low amounts of CH2Cl2 were seen in all treatments. Plans are underway to repeat this experiment and use a cryo-GC capability that will allow simultaneous determination of CO as well as the chlorinated methanes. This is important because CO represents the end product of the second hypothetical dechlorination pathway that may compete with the CHCl3 pathway and will aid in mass balance calculations. An additional experiment to evaluate the Henry's Law constant for CCl4 in aqueous solutions in the presence and absence of clay showed no significant difference due to the presence of clay, although slightly higher gas-phase concentrations were seen when clay was present.

Physical Description

vp.

Source

  • Other Information: PBD: 1 Jun 2003

Language

Item Type

Identifier

Unique identifying numbers for this report in the Digital Library or other systems.

  • Report No.: EMSP-86820A--2003
  • Grant Number: FG07-02ER63485
  • DOI: 10.2172/836460 | External Link
  • Office of Scientific & Technical Information Report Number: 836460
  • Archival Resource Key: ark:/67531/metadc782730

Collections

This report is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

What responsibilities do I have when using this report?

When

Dates and time periods associated with this report.

Creation Date

  • June 1, 2003

Added to The UNT Digital Library

  • Dec. 3, 2015, 9:30 a.m.

Description Last Updated

  • June 10, 2016, 6:43 p.m.

Usage Statistics

When was this report last used?

Yesterday: 0
Past 30 days: 0
Total Uses: 4

Interact With This Report

Here are some suggestions for what to do next.

Enlarge

PDF Version Also Available for Download.

Citations, Rights, Re-Use

Tratnyek, Paul G. Overcoming Barriers to the Remediation of Carbon Tetrachloride Through Manipulation of Competing Reaction Mechanisms, report, June 1, 2003; United States. (digital.library.unt.edu/ark:/67531/metadc782730/: accessed April 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.