Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Reduction Kinetics of Polymeric (Soluble) Manganese (IV) Oxide (MnO2) by Ferrous Iron (Fe2+)

Reduction Kinetics of Polymeric (Soluble) Manganese (IV) Oxide (MnO2) by Ferrous Iron (Fe2+) In numerous freshwater and marine environments, ferrous iron (Fe2+) can react with manganese oxides in a redox reaction. However, there are few quantitative data describing reaction rates. A “soluble” (colloidal and nanoparticulate) phase manganese dioxide (MnO2) was used to obtain kinetic data on MnO2 reduction by Fe2+ with a stopped flow UV–Vis method. Stopped flow experiments were carried out in unbuffered solutions between pH 4.9 and 5.36 and also at pH 7. The reaction was determined to be first order with respect to MnO2 and Fe2+ and second order overall. It is important to subtract absorbance of Fe(III) products from the UV–Vis data and to acquire data from the first milliseconds of the reaction. After subtracting Fe(III) product absorbance, the average second-order rate constant was determined to be 4338 ± 249 M−1 s−1 at 25 °C and pH 5. Reactions of 5 μM MnO2 with 50 and 100 μM Fe2+ were more than 50 % complete in 1.77 and 0.7 s, respectively. The reaction is an inner sphere electron transfer process as an outer sphere process is symmetry-forbidden. Studies show that Mn(III) intermediates are produced during the reaction. The fast kinetics makes this reaction significant to consider when modeling manganese oxide and reduced iron in environmental redox systems. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aquatic Geochemistry Springer Journals

Reduction Kinetics of Polymeric (Soluble) Manganese (IV) Oxide (MnO2) by Ferrous Iron (Fe2+)

Loading next page...
 
/lp/springer-journals/reduction-kinetics-of-polymeric-soluble-manganese-iv-oxide-mno2-by-qh7mqVnaFv

References (30)

Publisher
Springer Journals
Copyright
Copyright © 2015 by Springer Science+Business Media Dordrecht
Subject
Earth Sciences; Geochemistry; Hydrology/Water Resources; Hydrogeology
ISSN
1380-6165
eISSN
1573-1421
DOI
10.1007/s10498-015-9257-z
Publisher site
See Article on Publisher Site

Abstract

In numerous freshwater and marine environments, ferrous iron (Fe2+) can react with manganese oxides in a redox reaction. However, there are few quantitative data describing reaction rates. A “soluble” (colloidal and nanoparticulate) phase manganese dioxide (MnO2) was used to obtain kinetic data on MnO2 reduction by Fe2+ with a stopped flow UV–Vis method. Stopped flow experiments were carried out in unbuffered solutions between pH 4.9 and 5.36 and also at pH 7. The reaction was determined to be first order with respect to MnO2 and Fe2+ and second order overall. It is important to subtract absorbance of Fe(III) products from the UV–Vis data and to acquire data from the first milliseconds of the reaction. After subtracting Fe(III) product absorbance, the average second-order rate constant was determined to be 4338 ± 249 M−1 s−1 at 25 °C and pH 5. Reactions of 5 μM MnO2 with 50 and 100 μM Fe2+ were more than 50 % complete in 1.77 and 0.7 s, respectively. The reaction is an inner sphere electron transfer process as an outer sphere process is symmetry-forbidden. Studies show that Mn(III) intermediates are produced during the reaction. The fast kinetics makes this reaction significant to consider when modeling manganese oxide and reduced iron in environmental redox systems.

Journal

Aquatic GeochemistrySpringer Journals

Published: Mar 13, 2015

There are no references for this article.