Gas treatment of Cr(VI)-contaminated sediment samples from the North 60`s pits of the chemical waste landfill

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Description

Twenty sediment samples were collected at depths ranging from 5 to 100 ft (1.5 to 30 m) beneath a metal-contaminated plating-waste site and extensively characterized for Cr(VI) content and environmental availability. Three samples were selected for treatment with diluted gas mixtures with the objective of converting Cr(VI) to Cr(III), which is relatively nontoxic and immobile. These tests were designed to provide information needed to evaluate the potential application of gas injection as an in situ remediation technique. Gas treatment was performed in small columns (4.9-cm ID, 6.4- to 13.9-cm long) using 100 ppm ({mu}L L{sup -1}) H{sub 2}S or ethylene ... continued below

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67 p.

Creation Information

Thornton, E.C. & Amonette, J.E. December 1, 1997.

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  • Pacific Northwest Laboratory
    Publisher Info: Pacific Northwest Lab., Richland, WA (United States)
    Place of Publication: Richland, Washington

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Description

Twenty sediment samples were collected at depths ranging from 5 to 100 ft (1.5 to 30 m) beneath a metal-contaminated plating-waste site and extensively characterized for Cr(VI) content and environmental availability. Three samples were selected for treatment with diluted gas mixtures with the objective of converting Cr(VI) to Cr(III), which is relatively nontoxic and immobile. These tests were designed to provide information needed to evaluate the potential application of gas injection as an in situ remediation technique. Gas treatment was performed in small columns (4.9-cm ID, 6.4- to 13.9-cm long) using 100 ppm ({mu}L L{sup -1}) H{sub 2}S or ethylene mixtures in N{sub 2}. Treatment progress during the tests involving H{sub 2}S was assessed by monitoring the breakthrough of H{sub 2}S. Evaluation of H{sub 2}S treatment efficacy included (1) water-leaching of treated and untreated columns for ten days, (2) repetitive extraction of treated and untreated subsamples by water, 0.01 M phosphate (pH 7) or 6 M HCl solutions, and (3) Cr K-edge X-ray absorption near-edge structure (XANES) spectroscopy of treated and untreated subsamples. Results of the water-leaching studies showed that the H{sub 2}S treatment decreased Cr(VI) levels in the column effluent by 90% to nearly 100%. Repetitive extractions by water and phosphate solutions echoed these results, and the extraction by HCl released only 35-40% as much Cr in the treated as in the untreated samples. Analysis by XANES spectroscopy showed that a substantial portion of the Cr in the samples remained as Cr(VI) after treatment, even though it was not available to the water and phosphate extracting solutions. These results suggest that this residual Cr(VI) is present in low solubility phases such as PbCrO{sub 4} or sequestered in unreacted grain interiors under impermeable coatings formed during H{sub 2}S treatment. However, this fraction is essentially immobile and thus unavailable to the environment.

Physical Description

67 p.

Notes

INIS; OSTI as DE98051354

Source

  • Other Information: PBD: Dec 1997

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  • Other: DE98051354
  • Report No.: PNNL--11634
  • Grant Number: AC06-76RL01830
  • DOI: 10.2172/565355 | External Link
  • Office of Scientific & Technical Information Report Number: 565355
  • Archival Resource Key: ark:/67531/metadc690795

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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.

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Creation Date

  • December 1, 1997

Added to The UNT Digital Library

  • Aug. 14, 2015, 8:43 a.m.

Description Last Updated

  • June 14, 2016, 3:18 p.m.

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Thornton, E.C. & Amonette, J.E. Gas treatment of Cr(VI)-contaminated sediment samples from the North 60`s pits of the chemical waste landfill, report, December 1, 1997; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc690795/: accessed November 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.