Collect. Czech. Chem. Commun. 1992, 57, 1210-1217

Kinetics of Autocatalytic Oxidation of Mn(II) Ions by Periodate in Relation to Manganese Oscillations

Gongoryn Sodnomdordža, Milan Melicharčíkb and Ľudovít Treindlc

a Faculty of Natural Sciences, Mongolian State University, Ulaanbaatar, Mongolia
b Department of Chemistry, Pedagogical Faculty, 975 49 Banská Bystrica, Czechoslovakia
c Department of Physical Chemistry, Comenius University, 842 15 Bratislava, Czechoslovakia


The kinetics of the autocatalytic oxidation of Mn(II) ions by periodate was investigated in unbuffered phosphoric acid solutions and in buffered solutions; the process was studied in a bath reactor in relation to the chemical oscillations in a continuously flow stirred tank reactor (CSTR), which are based on the chemistry of manganese. The rate constants k1 and k'2 corresponding to the noncatalyzed and catalyzed reaction course were determined by the Schwartz method. While MnO4- ions are the reaction product in the unbuffered phosphoric acid medium, in a CH3COOH-NaOH buffer the Mn2+ ions are only oxidized to Mn(IV). For this case, a reaction pathway is discussed where the key step encompasses dimerization of MnO(OH)+ ions followed by the formation of (MnO2)col colloids, stabilized by adsorption of H2PO4- ions on their surface. This reaction pathway is also of importance with respect to the new manganese oscillator which is based on the autocatalytic oxidation of Mn(II) ions by periodate in a CSTR.