Identification of organic acids and other intermediates in oxidative degradation of chlorinated ethanes on TiO[sub 2] surfaces en route to mineralization. A combined photocatalytic and radiation chemical study. [gamma radiolysis]

Journal Article · Thu Nov 28 04:00:00 EST 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100177a085· OSTI ID:6923506

Mao, Yun; Schoeneich, C; Asmus, K D ^[1]

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1. Hahn-Meitner Inst., Berlin (Germany)

The oxidative degradation of chlorinated ethanes proceeds practically via the same mechanism in [gamma]-radiolysis and photocatalysis at TiO[sub 2] surfaces, respectively. C-centered radicals generated via hydroxyl radical induced C-H bond cleavage and peroxyl radicals derived therefrom after oxygen addition are the key radical intermediates in these processes. The main molecular products identified and isolated in both the [gamma]-radiolytic and photocatalytic experiments are organic (mostly chlorinated) acids, HCl, and CO[sub 2]. Other products formed in minor yields are aldehydes and HCOOH. Photocatalytic degradation of these product acids and nonionic substrates leads eventually to complete mineralization. The results strongly suggest that the photocatalytic degradation is initiated by an oxidation of the chlorinated compounds through TiO[sub 2]-surface-adsorbed hydroxyl radicals. Only some acids, like trichloroacetic acid and oxalic acid, seem to be oxidized primarily by valence band holes via a photo-Kolbe process. Several rate constants are reported on the oxidation of chlorinated ethanes and acids by free and surface-adsorbed hydroxyl radicals and on the overall photocatalytic degradation of the chlorinated compounds. The paper also includes a discussion of the material balance. The study demonstrates the value of radiation chemical investigations for the understanding of the details in the photocatalytic mineralization process of halogenated organic compounds.

• OSTI ID: 6923506
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:24; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400500* -- Photochemistry
400600 -- Radiation Chemistry
ALKYL RADICALS
CATALYSIS
CHALCOGENIDES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
DATA
DECOMPOSITION
ELECTROMAGNETIC RADIATION
EXPERIMENTAL DATA
GAMMA RADIATION
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROXYL RADICALS
INFORMATION
IONIZING RADIATIONS
KINETICS
MECHANICAL STRUCTURES
MINERALIZATION
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PEROXY RADICALS
PHOTOCHEMICAL REACTIONS
RADIATION EFFECTS
RADIATIONS
RADICALS
RADIOLYSIS
REACTION INTERMEDIATES
REACTION KINETICS
SUPPORTS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS