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 radio lysis radicals, O-.-, e(aq)(-) and (OH)-O-. with IO3- has been determi ned using electron pulse radiolysis and absorption spectroscopy. The t ransient growth of the IO4.2- species at 360 nm, formed by the oxide r adical addition to iodate, was used to determine its reaction rate con stant 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). T he equivalent values for hydrated electron reaction with iodate, obtai ned 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-k inetics 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 ener gy of 26.5 +/- 2.8 kJ mol(-1).