Visualizing Redox Chemistry: Probing Environmental Oxidation–Reduction Reactions with Indicator Dyes

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 6 Issue 3 (2001) pp 172-179

Visualizing Redox Chemistry: Probing Environmental Oxidation–Reduction Reactions with Indicator Dyes

Paul G. Tratnyek,^*,† Thea E. Reilkoff,^† Anthony W. Lemon,^† Michelle M. Scherer,^† Barbara A. Balko,^§ Linda M. Feik,^** and Brad D. Henegar^††

Department of Environmental Science and Engineering, Oregon Graduate Institute of Science & Technology^†, Portland, OR 97291, tratnyek@ese.ogi.edu, Department of Chemistry, Lewis & Clark College^§, Portland, OR 97219, Westview High School^**, Portland, OR, and Banks High School^††, Banks, OR
Received November 13, 2000. Accepted January 12, 2001

Published online: 27 April 2001

Abstract. One of the important questions in the chemistry of pollutant degradation is the identity and distribution of chemical agents that are responsible for reduction reactions in the environment. Reduction occurs primarily in water-saturated environments, such as sediments, soils, and sludges. Redox indicators can be used (i) as chemical probes to obtain fundamental insights into biogeochemical processes and (ii) as the basis for demonstrations suitable for teaching aspects of environmental chemistry. This paper explores the latter with examples that involve a variety of indicators (indigo sulfonates, resazurin, etc.), environmental media (anaerobic sediments and granular iron metal), and physico-chemical processes (oxidation–reduction, adsorption, and diffusion). The results show that reduction by either media (sediments or iron metal) is primarily, although not always entirely, a surface reaction. This situation results in indicator behavior that is interesting and challenging for students with a wide range of backgrounds.

Key Words: Laboratories and Demonstrations; environmental chemistry; redox reactions; UV-vis spectroscopy; indicator dyes; kinetics

(*) Corresponding author. (E-mail: tratnyek@ese.ogi.edu)

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