Pilot-Scale Reactor for Electrochemical Reduction of Nitroaromatics in Water. Simulated Wastewater Testing

Abstract

Abstract : The large-scale manufacture and use of nitroaromatic compounds such as TNT, DNT, and RDX has led to significant production of munitions wastewater. Wastewater containing these compounds is commonly referred to as pinkwater. The United States ceased production of TNT in the mid-l98Os, but TNT-contaminated wastewater generation still exists as a result of demilitarization. Both TNT and DNT are listed as priority pollutants by the U.S. Environmental Protection Agency because of their toxicology hazards. This study used an existing pilot-scale reactor, which was modified to account for mass transfer limitations observed in a previous study, to evaluate the performance of the modified reactor for electrochemical reduction of simulated munitions wastewater and pinkwater. Kinetic rate determination of RDX, HMX (a military explosive), and Tritanol (munitions wastewater with suspected aluminum and iron metal ions) reduction was studied at the bench-scale in an electrochemical batch reactor. These experiments yielded low rate constants. Continuous flow experiments conducted on the modified reactor showed very low DNT reduction. End product studies for batch simulation experiments conducted on the pilot-scale reactor showed a mass balance of 60 to 90 percent, and most of the intermediates were observed in the solid phase. Based on these results, continuous flow experiments were conducted on the pilot-scale reactor. A DNT reduction of about 80 percent could be attained for these experiments. End product studies conducted on the continuous flow experiments showed a mass balance of about 100 percent, with 80 percent of the intermediates observed in the solid phase.