Electrochemical Reduction of 2,4,6-Trinitrotoluene

Abstract

A laboratory-scale reactor was used to study the electrochemical reduction of 2,4,6-trinitrotoluene (TNT). A graphite cylinder impregnated with glassy carbon (zero porosity) was used as the cathode, and a platinum wire was used as the anode. Initially, experiments simulating batch conditions were conducted to evaluate the effect of electrolyte type, molar concentration of the electrolyte, and the applied current on the reduction kinetics of TNT. Results showed that the rate of TNT reduction increased with an increase in molar concentration of the electrolyte and the applied current. For the various currents studied, no significant changes in rate constants were observed for experiments conducted with sodium sulfate or lithium sulfate as electrolyte in the feed. Continuous flow experiments were conducted to evaluate the performance of the reactor. Three different currents (150, 200, and 250 mA) using 6 and 9 mM concentration of sodium sulfite as the electrolyte were used. Sodium sulfite was used as the electrolyte in the feed to maintain strict anoxic conditions, thereby preventing the formation of solid dimers. Under undetectable dissolved oxygen concentration levels in the system, the reactor operated continuously at a stable performance for the total experimental period conducted (105 days). On average, TNT reduction efficiency in the mid-80% levels was achieved for the three currents studied. The only intermediate observed in the aqueous phase was 2,4,6-trimainotoluene (TAT). A mole balance closure of 85–92% was achieved. A combined overall TNT reduction efficiency over 99% was achieved by using three reactors in series.