Electrolytic reduction of low molecular weight chlorinated aliphatic compounds: Structural and thermodynamic effects on process kinetics
A series of chlorinated low molecular weight alkanes and alkenes was transformed electrolytically using a porous nickel cathode at potentials from {minus}0.3 to {minus}1.4 V (versus standard hydrogen electrode). Kinetics were first-order with respect to the concentration of the halogenated targets. The dependence of the first-order rate constants on cathode potential followed the Butler-Volmer equation, modified to account for mass transfer resistance to reaction. The mass-transfer-limited rate constant for reaction of all species was about 1.55 L m{sup {minus}2} min{sup {minus}1}. Log-transformed reaction rate constants for reduction of chlorinated alkanes, derived via experiments at the same cathode potential (E{sub c} = {minus}1.0 or {minus}1.2 V vs SHE), were linearly related to carbon-halogen bond enthalpies, as expected based on a physical model that was developed from transition state theory. The chlorinated ethenes reacted much faster than predicted from bond enthalpy calculations and the alkane-based correlation, suggesting that alkenes are not transformed via the same mechanism as the chlorinated alkanes. Dihalo-elimination was the predominant pathway for reduction of vicinal polychlorinated alkanes. For chlorinated alkenes and germinal chlorinated alkanes, sequential hydrogenolysis was the major reaction pathway.
- Research Organization:
- Univ. of Arizona, Tucson, AZ (US)
- OSTI ID:
- 20023206
- Journal Information:
- Environmental Science and Technology, Vol. 34, Issue 5; Other Information: PBD: 1 Mar 2000; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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