Chemical mechanism of inorganic oxidants in the TiO2/UV process: increased rates of degradation of chlorinated hydrocarbons

Autor:	Michael R. Hoffmann, Albert T. Lee, Scot T. Martin
Rok vydání:	1995
Předmět:	chemistry.chemical_compound Light intensity Hydrolysis Reaction rate constant Autoxidation chemistry Environmental Chemistry Reactivity (chemistry) Oxyanion General Chemistry Photodegradation Photochemistry Chemical decomposition
Zdroj:	Environmental Science & Technology. 29:2567-2573
ISSN:	1520-5851 0013-936X
DOI:	10.1021/es00010a017
Popis:	Particulate suspensions of TiO_2 irradiated with UV light at wavelengths shorter than 385 nm catalyze the autooxidation of chlorinated hydrocarbons such as 4-chlorophenol (4-CP). The addition of oxyanion oxidants such as CIO_2^-, CIO_3^-, IO_4^-, S_2O_8^(2-), and BrO_3^- increases the rate of photodegradation of 4-CP in the following order: CIO_2^- > IO_4^- > BrO_3^- > CIO_3^-. In the absence of TiO_2, CIO_3^- shows no photoreactivity toward 4-CP, while HSO_5^- and MnO_4^- exhibit rapid thermal reactivity with 4-CP. BrO_3^- appears to increase photoreactivity by scavenging conduction-band electrons and reducing charge-carrier recombination. With CIO_3^- as an oxidant, the degradation of 4-CP appears to follow three concurrent pathways. Kinetic equations for the rate of degradation of 4-CP as a function of [4-CP], [CIO_3^-], and [O_2] and of the light intensity are derived from a proposed mechanism.
Databáze:	OpenAIRE
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