Photocatalytic degradation of 5-Nitro-1,2,4-Triazol-3-one NTO in aqueous suspention of TiO2. Comparison with fenton oxidation.

5-nitro-1,2,4-triazol-3-one (NTO) is a powerful insensitive explosive, present in industrial waste waters. A remediation method based on photochemical decomposition and Fenton oxidation of NTO has been evaluated by monitoring the mineralization of 14C-labelled NTO. The TiO2-catalyzed photodegradation (α>290nm, Ti02 0.4 g/1, NTO 150 mg/1)) leads to the complete mineralization of NTO in 3 hours. This degradation involves a simultaneous denitrification and ring scission of NTO leading to nitrites , nitrates and carbon dioxide. No significant photo-degradation of NTO was detected in the absence of the catalyst. Long term irradiation over one week, leads to a complete degradation of concentrated NTO (5g/1), suggesting that this method could be useful to clean-up NTO wastes. Fenton oxidation offers an efficient cost-effective method for NTO remediation. This reaction is faster that the TiO2 catalyzed photolysis and find application on the mineralization of high concentrations of NTO (15 g/1). Fenton oxidation provokes ring cleavage and subsequent elimination of the two carbon atoms of NTO as CO2, During this reaction, the nitro group is completely transformed into nitrates.