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Published August 1993 | public
Journal Article

Photocatalytic Degradation of Pentachlorophenol on TiO_2 Particles: Identification of Intermediates and Mechanism of Reaction

Abstract

The photoassisted oxidation of pentachlorophenol (PCP) in TiO_2 particle suspensions was investigated. Complete dechlorination of 47 µM PCP was achieved after 3 h of illumination at high intensity with apparent quantum efficiencies (ΦPCP, ΦCI, ΦH+, ΦH_2O_2) ranging from 1 to 3%. p-Chloranil, tetrachlorohydroquinone, H_2O_2, and o-chloranil were formed as the principal intermediates. Formate and acetate were formed as products during the latter stages of photooxidation. The mechanism for photooxidation of PCP proceeds via hydroxyl radical attack on the para position of the PCP ring to form a semiquinone radical which in turn disproportionates to yield p-chloranil and tetrachlorohydroquinone. Under high-intensity illumination, the reaction intermediates are attacked further by •OH to yield HCO_2^-, CH_3CO_2^-, CO_2, H^+, and Cl^-.

Additional Information

© 1883 American Chemical Society. Received for review July 6, 1992. Revised manuscript received April 13, 1993. Accepted May 13,1993. Publication Date: August 1993. With are grateful to the U.S. Environmental Protection Agency (Grant R813326-01-0) for the financial resources to pursue this project and to the Degussa Corporation for a gift of the titanium dioxide.

Additional details

Created:
August 20, 2023
Modified:
October 23, 2023