Kinetics and mechanism of the hydrolytic disproportionation of iodine

Kinetics of the hydrolytic disproportionation of I-2 3l(2) + 3H(2)O double left right arrow IO3- + 5l(-) + 6H(+) was studied by UV-VIS spectrophotometry at 298 K and at the ionic strength 0.2 M (NaClO4) in buffered solutions in the pH range 8.91-10.50 at different initial iodide concentrations. The characterization of this reaction is fundamental for modeling oscillatory and front reactions in the presence of iodine as reactant or intermediate as well as for drinking water treatment. A matrix rank analysis confirmed three absorbing species in the beginning of the reaction, whereas later assumption of two species is enough to describe the experimental data in the visible part of the spectrum. A reaction mechanism was proposed for disproportionation by using fitting/simulation with a multipurpose program package ZiTa, by simultaneous evaluation of 17,906 points in 79 experimental curves. A parameter set was suggested, which was obtained by absolute, relative, and orthogonal fittings of the experimental data. (C) 2004 Wiley Periodicals, Inc.