New Insights into the Photochemical Degradation of the Insensitive Munition Formulation IMX-101 in Water.

This study describes photolysis of the insensitive munition formulation IMX-101 [2,4-dinitroanisole (DNAN), NQ (nitroguanidine), and 3-nitro-1,2,4-triazol-5-one (NTO)] in aqueous solutions using a solar simulating photoreactor. Due to a large variance in the water solubility of the three constituents DNAN (276 mg L), NQ (5,000 mg L), and NTO (16,642 mg L), two solutions of IMX-101 were prepared: one with low concentration (109.3 mg L) and another with high concentration (2831 mg L). The degradation rate constants of DNAN, NQ, and NTO (0.137, 0.075, and 0.202 d, respectively) in the low concentration solution were lower than those of the individually photolyzed components (0.262, 1.181, and 0.349 d, respectively). In the high concentration solution, the molar loss of NTO was 4.3 times higher than that of NQ after 7 days of irradiation, although NQ was two times more concentrated and that NQ alone degraded faster than NTO. In addition to the known degradation products, DNAN removal in IMX-101 was accompanied by multiple productions of methoxydinitrophenols, which were not observed during photolysis of DNAN alone. One route for the formation of methoxydinitrophenols was suggested to involve photonitration of the DNAN photoproduct methoxynitrophenol during simultaneous photodenitration of NQ and NTO in IMX-101. Indeed, when DNAN was photolyzed in the presence of NO-labeled explosive CL-20, we detected methoxydinitrophenols with an increase of 1 mass unit, indicating that denitration of DNAN and renitration of products simultaneously occurred. As was the case with DNAN, we found that guanidine, a primary degradation product of NQ, also underwent renitration in the presence of NTO and the photocatalyst TiO. We concluded that the three constituents of IMX-101 can be photodegraded in surface water and that fate and primary degradation products of IMX-101 can be influenced by the interactions between the formulation ingredients and their degradation products.