HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Elprince, A. M. Articles by Mohamed, W. H. Search for Related Content PubMed Articles by Elprince, A. M. Articles by Mohamed, W. H. Agricola Articles by Elprince, A. M. Articles by Mohamed, W. H.

Catalytic Decomposition Kinetics of Aqueous Hydrogen Peroxide and Solid Magnesium Peroxide By Birnessite

Kuwait Institute for Scientific Research, P.O. Box 24885, Safat 13109, Kuwait

W. H. Mohamed

Dep. of Soils and Agricultural Chemistry, Alexandria Univ., Alexandria, Egypt

* Corresponding author.

ABSTRACT

Peroxides are used as O₂-generating agents. The decomposition of H₂O₂ (aq) or MgO₂(s) in the presence of synthetic birnessite [-MnO₂(s)] as a catalyst was observed by measuring the volume of O₂(g) given off. The experimental data fit a first-order kinetic law and the mechanism proposed by Habes and Weiss can explain the experimental results obtained for the decomposition of H₂O₂(aq). The applicability of the proposed mechanism involving H₂O₂(aq) was based on the following: (i) the activation energy was relatively high (82 ± 3 kJ mol^–1); (ii) the rate constant (k) was pH dependent, indicating that H⁺ and OH^- ions were formed in the process; (iii) a linear relationship (and not logarithmic) between k and the ionic strength indicated a reaction between an ion and a neutral molecule; and (iv) using birnessite with different fractional coverages of Co indicated that the reaction was heterogeneously catalyzed by Mn^z+1/Mn^z active centers. Regarding MgO₂(s) decomposition, the experimental data obtained at pH 7.6 followed a rate law derived from a shrinking-core model for fixed-size particles. The rate of the reaction was controlled by diffusion through the Mg(OH)₂(s) product layer rather than by chemical reaction at the core surface. Compared with ionic peroxides, MgO₂(s) could be a potential O₂-generating agent for generating O₂(g) during a relatively long period of time.

Received for publication August 5, 1991.

This article has been cited by other articles:

				A. M. Elprince, W. H. Mohamed, and E. M. El-Wakil Kinetics of Nonenzymatic Decomposition of Hydrogen Peroxide by Torrifluvents Soil Sci. Soc. Am. J., January 11, 2008; 72(1): 83 - 89. [Abstract] [Full Text] [PDF]