Radiolysis of aqueous solutions of TNT was examined to provide fundamental information concerning the reactions of TNT with radical species in water. χ-Radiation was used in conjunction with radical scavengers to compare yields for radiation-induced TNT transformation under oxidizing end reducing conditions and in the presence and absence of oxygen. Pulse radiolytic techniques were employed to determine rate constants and absorption spectra for the reactions of TNT with the hydroxyl radical and the aqueous electron. TNT was rapidly transformed under both reducing (1% tert- butyl alcohol, N2 sparged) and oxidizing (N20 sparged) conditions although rates under reducing conditions were greater. The initial yield for transformation of a 350 μmol L-1 TNT solution under reducing conditions was 0.14 μmol/J as opposed to 0,10 μmol/J measured in oxidizing conditions. The reactions of TNT with reduced oxygen species were found to be highly inefficient in aqueous solution. Although TNT is transformed by both oxidizing and reducing radicals, TNT degradation yields in the absence of a radical scavenger were low, indicating that under these conditions there were significant secondary reactions in which the species resulting from reactions between TNT and the primary radicals further reacted to reform the parent compound. The bimolecular rate constant for the reaction between TNT and ·OH was determined to be 4.3 x 108 mol-1 s-1. Byproduct analyses from χ- radiolysis suggest that hydroxyl radical abstraction of a methyl hydrogen to form the trinitrotoluyl radical is an initial oxidative reaction. The bimolecular rate constant for the reaction between TNT and e(aq)- was measured as 3.5 x 1010 mol-1 s-1. These results provide quantitative and qualitative insight into the reactions between TNT and the various aqueous radicals produced in many remediation processes.
ASJC Scopus subject areas
- Environmental Chemistry