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Kinetics and Mechanism of the Enhanced Reductive Degradation of CCl_4 by Elemental Iron in the Presence of Ultrasound

Hung, Hui-Ming and Hoffmann, Michael R. (1998) Kinetics and Mechanism of the Enhanced Reductive Degradation of CCl_4 by Elemental Iron in the Presence of Ultrasound. Environmental Science and Technology, 32 (19). pp. 3011-3016. ISSN 0013-936X. https://resolver.caltech.edu/CaltechAUTHORS:20150807-112624837

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Abstract

Enhanced rates of sonolytic degradation of CCl_4 in the presence of Fe^0 are demonstrated. In Ar-saturated solutions, the first-order rate constant for CCl_4 degradation is k_(US) = 0.107 min^(-1), whereas in the presence of Ar and Fe^0, the apparent first-order rate constant is found to depend on the total surface area of elemental iron in the following fashion:  k_(obs) = (k_(US) + k_(Fe)^0A_(Fe)^0) min^(-1), where k^(US) = 0.107 min^(-1), k_(Fe)^0 = 0.105 L m_(-2) min^(-1), and A_(Fe)^0) = reactive surface area of Fe^0 in units of m^2 L^(-1). In the coupled ultrasound and iron system, the contribution to the overall degradation rate by direct reaction with Fe^0 results in an overall rate enhancement by a factor of 40. These enhancements are attributed (1) to the continuous cleaning and chemical activation of the Fe^0 surface by the combined chemical and physical effects of acoustic cavitation and (2) to accelerated mass transport rates of reactants to the Fe^0 surfaces. Additional kinetic enhancements are due to the production of H^+ during the course of the reaction. Furthermore, the concentrations of the principal reaction intermediates, C_2Cl_6 and C_2Cl_4, are influenced substantially by the total available surface area of Fe^0.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/es980273iDOIArticle
http://pubs.acs.org/doi/abs/10.1021/es980273iPublisherArticle
ORCID:
AuthorORCID
Hung, Hui-Ming0000-0002-6755-6359
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 1998 American Chemical Society. Received for review March 17, 1998. Revised manuscript received June 1, 1998. Accepted June 15, 1998. Publication Date (Web): August 14, 1998. We appreciate the contributions by Dr. Weavers about the details of the kinetics and mechanisms. Financial support from the Office of Naval Research (NAV5-N0001492J1901; NAV1-N47408-97-M-0771) and the Department of Energy (DOE 1 963472402) is gratefully acknowledged.
Funders:
Funding AgencyGrant Number
Office of Naval Research (ONR)NAV5-N0001492J1901
Office of Naval Research (ONR)NAV1-N47408-97-M-0771
Department of Energy (DOE)DOE 1 963472402
Issue or Number:19
Record Number:CaltechAUTHORS:20150807-112624837
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150807-112624837
Official Citation:Kinetics and Mechanism of the Enhanced Reductive Degradation of CCl4 by Elemental Iron in the Presence of Ultrasound Hui-Ming Hung and Michael R. Hoffmann Environmental Science & Technology 1998 32 (19), 3011-3016 DOI: 10.1021/es980273i
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59319
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:07 Aug 2015 23:18
Last Modified:09 Mar 2020 13:18

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