Degradation of RDX by various advanced oxidation processes: I. Reaction rates

1, 3, 5-trinitrotriazacyclohexane (C3H6O6N6) or RDX is a heterocyclic nitramine compound that has been widely used as an explosive since the early 1900 s. There is substantial interest in removing this compound from groundwater and other environmental media. Advanced oxidation processes (AOPs) are currently being tested as a treatment process for this compound. In this research five types of oxidation processes (UV, UV/H2O2, ozone, ozone/H2O2, and UV/ozone) were used to degrade RDX. Samples were collected at various times during these processes and tested for residual RDX. Degradation rates of RDX by various AOPs were determined and the effect of some process parameters on the degradation rates examined. Oxidation of RDX was observed to be enhanced under conditions where hydroxyl radical formation could be maximized by adjusting the process parameters. Carbon and nitrogen balances were performed during RDX oxidation by the ozone/H2O2 process. While no mineralization of organic carbon was noted, approximately 50% of organic nitrogen was converted to nitrate during this process. This suggests that the carbon and nitrogen in the heterocyclic ring structure of RDX were oxidized to organic byproducts, while the nitro groups were oxidized to nitrate.