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 t he 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 whic h cannot be completely oxidised to CO2 is observed. Experiments perfor med under strictly oxidative conditions show higher yields of these in ert compounds and, hence, incomplete mineralization. Cyanide was forme d in concentrations lower than 5 x 10(-5) mol/l. In alkaline aqueous s olutions, cyanide is completely transformed into CO32-, NH4+ and NO3- during the irradiation time needed to mineralize the isoxazole. Theref ore, cyanide does not present a potential risk for the use of the VUV photolysis for isoxazole degradation. Similarly, organic nitrogen is c onverted into both, NO3- and NH4+. The relative concentrations of the two ions depend on total irradiation time, oxygen saturation and react or geometry. A sequence of reactions is proposed and discussed.