On the hydrolysis of iodine in alkaline solution: A radiation chemical study

A reaction set has been constructed that describes the radiolysis of N2O-saturated aqueous solutions of iodide ion. The kinetics and mechanism of the hydrolysis of iodine has been reassessed from conductivity measurements at pH 9.5-11.1 using pulse radiolysis (present work) and previously published data on the yields of 1(2)+I-3(-), HOI + IO- and IO3- produced by the gamma-radiolysis of unbuffered solutions [Buxton, G.V., Sellers, R.M., 1985. Radiation induced redox reactions of iodine species in aqueous solutions J. Chem. Soc., Faraday Trans. I 81, 449-471]. The conductivity data are consistent with a value of k(5)(I-2 + OH-) = 1 x 10(10) dm(3) mol(-1) s(-1) and with the other hydrolysis parameters having values in the following ranges: k(-8)(HOI + I-) = (0.3 - 3) x 10(9) dm(3) mol(-1) s(-1), K-5(I-2 + OH- empty set I2OH-) = 5-50dm(3) mol(-1), K-8(I2OH- empty set HOI + I-) = 8.3-0.83 mol dm(-3), based on K5K8 = 41.5. The values of K-5 obtained here are much smaller than the literature values of ca. 1.6 x 10(4) dm(3) mol(-1) [Lengyel, I., Epstein, I.R., Kustin, K., 1993. Kinetics of iodine hydrolysis. Inorg. Chem. 32, 5880-5882]. The gamma-radiolysis results are well described by these hydrolysis parameters. (C) 2006 Elsevier Ltd. All rights reserved.