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The Sonochemical Degradation of Azobenzene and Related Azo Dyes: Rate Enhancements via Fenton's Reactions

Joseph, Jiju M. and Destaillats, Hugo and Hung, Hui-Ming and Hoffmann, Michael R. (2000) The Sonochemical Degradation of Azobenzene and Related Azo Dyes: Rate Enhancements via Fenton's Reactions. Journal of Physical Chemistry A, 104 (2). pp. 301-307. ISSN 1089-5639. https://resolver.caltech.edu/CaltechAUTHORS:20150812-143043327

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Abstract

The sonochemical degradation of aqueous solutions of azobenzene and related azo dyes (methyl orange, o-methyl red, and p-methyl red) was performed at 500 kHz and 50 W, under air, O_2, or Ar saturation at 288 K. Reaction products and intermediates were identified by HPLC-ES-MS. Total organic carbon (TOC) was also determined as a function of reaction time. We propose a reaction mechanism based on the observed species and the extent and rate of TOC depletion. The addition of OH radicals to the azo double bond is considered to be the first step of the sequence of oxidative bond cleavages leading to the production of carboxylic acids, quinones, carbon dioxide, and nitrate ions as the main degradation products. The effects of the dye structures and of the background gas on the sonochemical bleaching rates were also investigated. The reaction rates for o-methyl red were approximately 30−40% faster than those for the other compounds. This appears to be a strong influence by a carboxylic group ortho to the azo group. Saturating with Ar instead of air or O_2 increased the pseudo first-order rate constants for the degradation by 10%. The acceleration of the sonochemical bleaching and the mineralization process upon addition of Fe(II) was also investigated in Ar-saturated methyl orange solutions. A 3-fold increase in the reaction rate was observed at optimal Fe(II) concentrations. This kinetic effect is quantitatively accounted for by a simple kinetic model based on the reaction of Fe(II) with sonochemically produced H_2O_2 (Fenton's reaction). This latter effect illustrates a simple way of achieving a substantial improvement in the efficiency of sonochemical degradation reactions.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/jp992354mDOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp992354mPublisherArticle
ORCID:
AuthorORCID
Hung, Hui-Ming0000-0002-6755-6359
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 2000 American Chemical Society. Received: July 14, 1999; In Final Form: October 29, 1999. Publication Date (Web): December 9, 1999. The authors thank Dr. A. J. Colussi and Dr. Peter Green for helpful discussions. Financial support provided by the Department of Energy (DOE 1963472402) and the U.S. Navy (N 47408-99-M-5049) is gratefully acknowledged. J.M.J. thanks the ICSC World Laboratory for a research fellowship.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DOE 1963472402
Office of Naval Research (ONR)N 47408-99-M-5049
ICSC World LaboratoryUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20150812-143043327
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150812-143043327
Official Citation:The Sonochemical Degradation of Azobenzene and Related Azo Dyes:  Rate Enhancements via Fenton's Reactions Jiju M. Joseph, Hugo Destaillats, Hui-Ming Hung, and Michael R. Hoffmann The Journal of Physical Chemistry A 2000 104 (2), 301-307 DOI: 10.1021/jp992354m
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59455
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:12 Aug 2015 22:21
Last Modified:09 Mar 2020 13:18

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