^*Correspondence to C. T. Aravindakumar, School of Chemical Sciences, Mahatma Gandhi University, Kottayam 686 560, Kerala, India.

Laser flash photolysis has been used to determine the bimolecular rate constants and the spectral nature of the intermediates obtained by the reaction of sulfate radical anion (SO₄^- ) with 1,3,5-triazine (T), 2,4,6-trimethoxy-1,3,5-triazine (TMT), 2,4-dioxohexahydro-1,3,5-triazine (DHT), and 6-chloro N-ethyl N’-(1-methylethyl)-1,3,5-triazine-2,4-diamine (atrazine, AT). The rate constants determined were in the range 4.6 × 10⁷-3 × 10⁹ dm³ mol^-1 s^-1 at pH 6. The transient absorption spectra obtained from the reaction of SO₄^- with T, TMT, DHT and AT has an absorption maximum in the region 320-350 nm and was found to undergo second-order decay. The intermediate species is assigned to N-yl C(OH) radical of T (TOH), carbon centered neutral radical of TMT, an OH-adduct of AT and an N-centered radical in the case of DHT. The interpretations on the experimental results obtained from TMT are supported by DFT calculation using Gaussian 03. Steady state radiolysis technique has also been used to investigate the degradation of AT induced by SO₄^-. The degradation profile indicated that about 99% of AT has been decomposed after an absorbed gamma-radiation dose of 7.5 kGy. The degradation yield of AT (expressed as G(-AT)) was found to be 0.26 µ mol J^-1. The degradation reactions initiated by SO₄^-  may thus be employed as a potential alternative for OH-induced degradation of triazines.

Copyright © 2007 John Wiley & Sons, Ltd.

The Abstract has been published at Wiley InterScience website and can be accessed from this link:

http://www3.interscience.wiley.com/cgi-bin/abstract/114102851/ABSTRACT