Dechlorination of chloromethanes on iron and palladium-iron bimetallic surface in aqueous systems
- Cleveland State Univ., OH (United States). Dept. of Chemistry
Iron granules and palladium-treated iron granules (Pd/Fe[sup 0]-H[sub 2]O) in contact with water have been tested as a potential means to dechlorinate chloromethanes (CCl[sub 4], CHCl[sub 3], and CH[sub 2]Cl[sub 2]) that are commonly generated in teaching chemistry laboratories. Palladium treatment enhanced the rate of dechlorination of CCl[sub 4] by a factor of about seven compared to the untreated Fe[sup 0]-H[sub 2]O, but the potential toxic effect of palladium remains a concern. Oxygen in the aqueous solution reduced the dechlorination rates of CCl[sub 4] with both Fe[sup 0]-H[sub 2]O and Pd/Fe[sup 0]-H[sub 2]O by at least a factor of three. Nevertheless, from the consideration of remediating solvent wastes, both systems appear suitable for treating CCl[sub 4] and possibly CHCl[sub 3] wastes, even in the presence of oxygen. The reactivities of the three chloromethanes toward the Fe[sup 0]-H[sub 2]O were vastly different. The dechlorination rate of CCl[sub 4] was by far the highest, followed by that of CHCl[sub 3], and CH[sub 2]Cl was virtually unreactive toward the Fe[sup 0]-H[sub 2]O system. Dechlorination reactions of CCl[sub 4] and CHCl[sub 3] were systematically examined on both Fe[sup 0]-H[sub 2]O and Pd/Fe[sup 0]-H[sub 2]O. On the basis of the data, it appears that CCl[sub 4] is successively dechlorinated to form CH[sub 4] via the formation of partially dechlorinated intermediates. Proton transfer to various intermediates produces the chloromethanes: CHCl[sub 3], CH[sub 2]Cl[sub 2], and CH[sub 3]Cl. Furthermore, CH[sub 4] formation, independent of the proton-transferring reactions, appears to be selectively stimulated by palladium.
- OSTI ID:
- 6406750
- Journal Information:
- Environmental Toxicology and Chemistry, Journal Name: Environmental Toxicology and Chemistry Vol. 18:6; ISSN ETOCDK; ISSN 0730-7268
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
540320 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
CHEMICAL REACTIONS
CHEMISTRY
CHLORINATED ALIPHATIC HYDROCARBONS
CONTROL
DECHLORINATION
DEHALOGENATION
ELEMENTS
HALOGENATED ALIPHATIC HYDROCARBONS
IRON
METALS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PALLADIUM
PLATINUM METALS
POLLUTION CONTROL
REMEDIAL ACTION
TRANSITION ELEMENTS
WATER CHEMISTRY
WATER POLLUTION CONTROL