Kinetics of transformation of 1,1,1-trichloroethane by Fe(II) in cement slurries

Bahngmi Jung, Bill Batchelor

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7 Citations (Scopus)

Abstract

This study examines the applicability of the iron-based degradative solidification/stabilization (DS/S-Fe(II)) process to 1,1,1-trichloroethane (1,1,1-TCA), which is one of common chlorinated aliphatic hydrocarbons (CAHs) of concern at contaminated sites. DS/S-Fe(II) combines contaminant degradation by Fe(II) and immobilization by the hydration reactions of Portland cement. The transformation of 1,1,1-TCA by Fe(II) in 10% Portland cement slurries was studied using a batch slurry reactor system. The effects of Fe(II) dose, pH, and initial concentration of 1,1,1-TCA on the kinetics of 1,1,1-TCA degradation were evaluated. Degradation of 1,1,1-TCA in cement slurries including Fe(II) was very rapid and could be described by a pseudo-first-order rate law. The half-lives for 1,1,1-TCA were measured between 0.4 and 5 h when Fe(II) dose ranged from 4.9 to 39.2 mM. The pseudo-first-order rate constant increased with pH to a maximum near pH 12.5. A saturation rate equation was able to predict degradation kinetics over a wide range of target organic concentrations and at higher Fe(II) doses. The major transformation product of 1,1,1-TCA in mixtures of Fe(II) and cement was 1,1-dichloroethane (1,1-DCA), which indicates that degradation occurred by a hydrogenolysis pathway. A small amount of ethane was observed. The conversion of 1,1,1-TCA to ethane was better described by a parallel reaction model than by a consecutive reaction model.

Original languageEnglish
Pages (from-to)1315-1321
Number of pages7
JournalJournal of Hazardous Materials
Volume163
Issue number2-3
DOIs
Publication statusPublished - 3 Apr 2009
Externally publishedYes

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Keywords

  • 1,1,1-Trichloroethane
  • Degradative solidification/stabilization
  • Fe(II)
  • Portland cement
  • Reductive dechlorination

ASJC Scopus subject areas

  • Environmental Chemistry
  • Environmental Engineering
  • Health, Toxicology and Mutagenesis
  • Pollution
  • Waste Management and Disposal

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