Reduction and conversion of 2,4,6-trinitrotoluene (TNT) by sulfide under simulated anaerobic conditions.

To account for the fast disappearance of TNT in anaerobic fermentative liquid, we investigated TNT (TNT0 = 50 mg/L) reduction by Na2S at 30 +/- 1 degrees C in two types of buffer systems, a phosphate buffer (PB, system A) and a CH3COOH-NaHCO3 buffer (system B). The effects of pH, sulfide concentration and buffer system on the conversion and reaction rate of TNT were investigated. The effect of different variables on the conversion of TNT decreased in the following order: Na2S concentration > pH > buffer system. A kinetics study showed that TNT reduction by Na2S occurred in two stages separated by a change point. The observed rate constants of the first stage Kobs-1 were 1 order of magnitude lower than those of the second stage. The TNT conversion rate increased and the time to reach the change point became shorter with increasing Na2S concentration and pH. A 5-fold increase in Na2S concentration above the theoretical stoichiometric concentration was optimum. Observed rate constants of the first stage Kobs-1 were proportional to the hydrosulfide ion concentration and the conversion rate of TNT was greater and faster in buffer system B than in system A. (C) 2010 Elsevier B.V. All rights reserved.