Kinetics of the methylene blue oxidation by cerium(iv) in sulphuric acid solutions

Katafias, A. and Kita, P. and Wrzeszcz, G. and Mills, A. (2007) Kinetics of the methylene blue oxidation by cerium(iv) in sulphuric acid solutions. Transition Metal Chemistry, 32 (1). pp. 31-37. ISSN 0340-4285 (http://dx.doi.org/10.1007/s11243-006-0120-3)

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Abstract

The oxidation of methylene blue (MB+) by cerium(IV) was studied in 0.1-5 M H2SO4. The reaction proceeds via MB radical (MB2+•) formed by one electron transfer to the oxidant. The radical is observed spectrophotometrically by a very intense absorbance at λmax = 526 nm and by the e.p.r signal at g = 2.000. The kinetics of the fast radical formation are two orders of magnitude slower than its decomposition, which were examined using a stopped-flow method at 298 K under pseudo-first order conditions. The rate laws for the both steps were determined and a likely mechanism reported.

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