OXIDATIVE-DEGRADATION OF NITROGEN-CONTAINING ORGANIC-COMPOUNDS - VACCUM-ULTRAVIOLET (VUV) PHOTOLYSIS OF AQUEOUS-SOLUTIONS OF 3-AMINO 5-METHYLISOXAZOLE

The oxidative degradation of 3-amino 5-methyl isoxazole initiated by the VUV photolysis of water at 172 nm has been studied. Mineralization of CO2, H2O, NO3- and NH4+ is more efficient when reductive conditions (argon saturated solutions) are Favoured. Formation of compounds which cannot be completely oxidised to CO2 is observed. Experiments performed under strictly oxidative conditions show higher yields of these inert compounds and, hence, incomplete mineralization. Cyanide was formed in concentrations lower than 5 x 10(-5) mol/l. In alkaline aqueous solutions, cyanide is completely transformed into CO32-, NH4+ and NO3- during the irradiation time needed to mineralize the isoxazole. Therefore, cyanide does not present a potential risk for the use of the VUV photolysis for isoxazole degradation. Similarly, organic nitrogen is converted into both, NO3- and NH4+. The relative concentrations of the two ions depend on total irradiation time, oxygen saturation and reactor geometry. A sequence of reactions is proposed and discussed.