Analytical Sciences

Kinetic Investigation of the Autocatalytic Reaction between Potassium Permanganate and Hydrogen Peroxide with Soft-modeling Methods

Yanyan LI, Yi ZHAO, and Zhongliang ZHU

Department of Chemistry, Tongji University, 1239 Siping Road, Shanghai 200092, P. R. China

The complex autocatalytic reaction between potassium permanganate (KMnO₄) and hydrogen peroxide (H₂O₂) was studied by online UV-Vis spectra methods. The kinetic profiles of the absorptive components, including KMnO₄ and two intermediates, were obtained by resolving the spectra-kinetic matrix with iterative target transformation factor analysis (ITTFA). But for the product Mn(II), which is not absorptive in the monitoring wavelength range, this was not applicable. Therefore, local mass balance region (LMBR) technique was proposed to get all of the scaled profiles, especially the non-absorptive components. Influences of various reaction conditions, such as concentrations of H₂O₂ and sulfuric acid (H₂SO₄) and reaction temperatures, were also investigated. Contrary to most other reactions, when initial concentrations of hydrogen peroxide ([H₂O₂]₀) are largely excessive ([H₂O₂]₀/[KMnO₄]₀ >40), higher [H₂O₂]₀ will decrease the degradation rate, while the higher temperature makes the reaction go much slower.

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