Arrhenius parameter determination for the reaction of the oxide radical, hydrated electron and hydroxyl radical with iodate in aqueous solution

The temperature dependence of the reactions of the primary water radiolysis radicals, O-.-, e(aq)(-) and (OH)-O-. with IO3- has been determined using electron pulse radiolysis and absorption spectroscopy. The transient growth of the IO4.2- species at 360 nm, formed by the oxide radical addition to iodate, was used to determine its reaction rate constant of(1.66 +/- 0.04) x 10(9) dm(3) mol(-1) s(-1) (22.1 degrees C), with a corresponding activation energy of 14.60 +/- 0.67 kJ mol(-1). The equivalent values for hydrated electron reaction with iodate, obtained by directly monitoring the e(aq)(-) decay at 700 nm were (5.49 +/- 0.15) x 10(9) dm(3) mol(-1) s(-1) (21.5 degrees C) and 8.86 +/- 0.26 kJ mol(-1), respectively. Arrhenius parameters for the reaction of the hydroxyl radical with iodate were determined using SCN- competition-kinetics and computer simulation, to give a rate constant of (1.08 +/- 0.48) x 10(5) dm(3) mol(-1) s(-1) (22.0 degrees C) and activation energy of 26.5 +/- 2.8 kJ mol(-1).