Fenton-enhanced gamma-radiolysis of cyanuric acid.

Degradation of cyanuric acid (OOOT), a stable end product of oxidative decomposition of atrazine, is investigated in a combined field of gamma radiolysis and fenton reaction. The reaction of hydroxyl radical (OH) at pH 6 was carried out by irradiating N(2)O saturated aqueous solutions containing OOOT (1 x 10(-3) mol dm(-3)), and this resulted only a marginal degradation (20%). However, when the same reaction was carried out in the presence of varying concentrations of ferrous sulfate ((5-10)x10(-5) mol dm(-3)), the decay of OOOT has been enhanced to more than 80%. This decay followed a first order kinetics. Nearly similar effects were observed with another triazine derivative, 2,4-dioxohexahydro-1,3,5-triazine (DHT). Two major reaction mechanisms are proposed for the enhanced decay of OOOT. The formation of unstable hydroxyl radical adducts from the reaction of .OH which is the result of gamma radiolysis and the Fenton reaction (resulting from the reaction of the added Fe(II) and of the H(2)O(2) from the radiolysis of water), is proposed as the first mechanism. The second mechanism, which is likely the major contributor to degradation, is proposed as the reaction of a nucleophilic adduct, Fe(II)OOH, which could directly react with the electron deficient triazine ring. It is highlighted that such degradation reactions must be explored for the complete degradation of the byproducts of the oxidative decomposition of atrazine.