FATE OF AMINO-ACIDS UPON EXPOSURE TO AQUEOUS TITANIA IRRADIATED WITH UV-A AND UV-B RADIATION - PHOTOCATALYZED FORMATION OF NH3, NO3- AND CO2

The fate of nitrogen in various amino acids was examined following the ir photooxidative (and/or reductive) transformation catalyzed by UV-A and UV-B illuminated aqueous TiO2 dispersions. The nitrogens in the am ino acids are photoconverted predominantly into NH, (analyzed as NH4+) and to a lesser extent into NO3- ions; NH4+/NO3- ratios span the rang e 3-12 after ca. 8 h irradiation. Extensive evolution of CO2 is also o bserved; in some cases it is quantitative. Variations in the NH4+/NO3- ratio in the transformation of amino acids are dependent on the subst rates molecular structure. Some of the steps in an otherwise complex m echanism of the heterogeneous photocatalyzedmineralization are describ ed. (C) 1997 Elsevier Science S.A.