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Electrochemical Reduction of Halogenated Alkanes and Alkenes Using Activated Carbon-Based Cathodes.
King, Jacob F; Mitch, William A.
Afiliação
  • King JF; Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, Palo Alto, California94305, United States.
  • Mitch WA; Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, Palo Alto, California94305, United States.
Environ Sci Technol ; 56(24): 17965-17976, 2022 12 20.
Article em En | MEDLINE | ID: mdl-36459429
ABSTRACT
Granular activated carbon (GAC) is used to sorb a broad range of halogenated contaminant classes, but spent GAC disposal is costly. Taking advantage of GAC's conductivity, this study evaluated the conversion of the GAC to cathodes for electrochemical reductive dehalogenation of 15 halogenated alkanes and alkenes exhibiting a diversity of structures (type of halogen, number of halogens, functional groups) and including contaminants of practical importance (e.g., trichloroethylene). Alkane degradation rates increased with the number of halogens and in the order chlorine < bromine < iodine. Quantitative structure-activity relationships (QSARs) correlating experimental first-order degradation rate constants for alkanes with molecular descriptors associated with an outer-sphere one-electron transfer calculated using density functional theory indicated that correlations with molecular descriptors improved in the order aqueous phase reduction potentials (E0,aq) < energy of the substrate's lowest unoccupied molecular orbital (ELUMO) < Marcus theory activation free energies (ΔG‡) ∼ gas-phase standard reduction free energies (ΔG0,gas). Chlorinated alkene degradation rates increased with decreasing number of chlorines, and QSAR correlations were opposite those of alkanes, indicating a different reaction mechanism. Degradation timescales ranged from 1 min to 3 h with halides as predominant products. These results suggest that the electrochemical reduction of halogenated alkanes and alkenes can be used to regenerate spent GAC.
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Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Carvão Vegetal / Alcanos Idioma: En Revista: Environ Sci Technol Ano de publicação: 2022 Tipo de documento: Article País de afiliação: Estados Unidos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Carvão Vegetal / Alcanos Idioma: En Revista: Environ Sci Technol Ano de publicação: 2022 Tipo de documento: Article País de afiliação: Estados Unidos