Kinetics of tetrachloroethylene-reductive dechlorination catalyzed by vitamin B{sub 12}

Journal Article · Tue Sep 01 04:00:00 EDT 1998 · Environmental Toxicology and Chemistry

DOI:https://doi.org/10.1002/etc.5620170906· OSTI ID:675410

Burris, D R ^[1]; Delcomyn, C A ^[2]; Deng, B ^[3]; Buck, L E ^[4]; Hatfield, K ^[5]

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1. AFRL/MLQR, Tyndall AFB, FL (United States)
2. Applied Research Associates, Inc., Tyndall AFB, FL (United States)
3. New Mexico Inst. of Mining and Technology, Socorro, NM (United States). Dept. of Mineral and Environmental Engineering
4. Polytechnic Univ., Brooklyn, NY (United States). Dept. of Civil and Environmental Engineering
5. Univ. of Florida, Gainesville, FL (United States). Dept. of Civil Engineering

Reductive dechlorination kinetics of tetrachloroethylene (PCE) to ethylene catalyzed by vitamin B{sub 12} using Ti[III] citrate as the bulk reductant was examined in a vapor-water batch system. A kinetic model incorporating substrate-B{sub 12} electron-transfer complex formation and subsequent product release was developed. The model also accounted for the primary reductive dechlorination pathways (hydrogenolysis and reductive {beta} elimination) and vapor/water-phase partitioning. Reaction rate constants were sequentially determined by fitting the model to experimental kinetic data while moving upward through consecutive reaction pathways. The release of product from the complex was found to be second order with respect to substrate concentration for both PCE and acetylene; all other substrates appeared to release by first order. Reductive {beta} elimination was found to be a significant reaction pathway for trichloroethylene (TCE), and chloroacetylene was observed as a reactive intermediate. Acetylene production appears to be primarily due to the reduction of chloroacetylene derived from TCE. The reduction of cis-dichloroethylene (cis-DCE), the primary DCE isomer formed, was extremely slow, leading to a significant buildup of cis-DCE. The kinetics of acetylene and vinyl chloride reduction appeared to be limited by the formation of relatively stable substrate-B{sub 12} complexes. The relatively simple model examined appears to adequately represent the main features of the experimental data.

• Sponsoring Organization: USDOE
• OSTI ID: 675410
• Journal Information: Environmental Toxicology and Chemistry, Journal Name: Environmental Toxicology and Chemistry Journal Issue: 9 Vol. 17; ISSN ETOCDK; ISSN 0730-7268
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
CHLORINATED ALIPHATIC HYDROCARBONS
DECHLORINATION
INDUSTRIAL WASTES
MATHEMATICAL MODELS
VITAMIN B-12
WASTE PROCESSING
WASTE WATER
WATER POLLUTION ABATEMENT