PH05 Fate and Effects of Energetic Compounds
Exhibit Hall
8:00 AM - Thursday
(PH029) Reductive degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX) with zero valent iron in the presence of electron transfer mediators.
Bae, B.1, Nurmi, J.2, Tratnyek, P.2, 1 Kyungwon University, Sungnam, Kyunggi, Rep. of Korea2 Oregon Health & Science University, Beaverton, Oregon, USA
ABSTRACT- The toxicity and mutagenicity of RDX poses significant environmental concerns in munitions contaminated soils and groundwaters near military ranges, munitions manufacturing plants, and disposal areas. The recent development of reductive transformation technologies with zero valent iron offers a new treatment scheme for remediating highly oxidized RDX contaminated groundwater. Most studies focus on the RDX reduction by Fe0 in controlled batch experiments. However, there is evidence that naturally-occurring compounds can enhance or retard the rate of contaminant degradation by Fe0. In this study, the rate of RDX degradation by Fe0 under various environmental conditions was studied and compared with the effects of naturally occurring electron transfer mediators. In a batch reactor containing electrolytic Fe0, RDX was sequentially reduced to polar intermediates which eventually disappeared, via mononitroso-RDX (MNX), dinitroso-RDX (DNX), and trinitroso-RDX (TNX) as the major intermediates. The rate of RDX reduction was best fitted by a pseudo-first order and the surface normalized rate constant, ksa, was estimated to be 0.0275 Lm-2min-1. However, the occurrence and longevity of partially reduced RDX varied depending on the RDX/iron mass ratio. At low iron mass concentrations, the nitroso-RDX intermediate were dominant and slowly degraded. On the contrary, low concentrations of MNX and DNX appeared in the early phase of the reaction at high iron mass concentration. In addition, the effects of electron transfer mediators on reduction of RDX are discussed.
Key words: RDX, Reductive degradation, Electron transfer mediator