Photoinduced transformation of glycerol in titania suspensions. (An EPR spin trapping study of radical intermediates).

Formation of radical intermediates upon photocatalytic (UVA) glycerol transformation in aerated aqueous TiO 2 (P25) suspensions was followed by EPR spin trapping technique. Character and concentration of the spin-adducts generated by the addition of the radical species to 5,5-dimethyl-1-pyrroline N -oxide (DMPO) spin trap are significantly affected by the UVA radiation dose and by the initial composition of the photocatalytic system. The DMPO spin-adducts of hydroxyalkyl radicals R1 and R2 detected in the aerated aqueous P25 suspensions containing glycerol are compatible with the H-abstraction processes attributed to the interaction of physisorbed glycerol molecules with the trapped holes or to the reaction of free hydroxyl radicals with glycerol in solution. Addition of fluoride at various concentrations has no effect on the character and concentration of DMPO spin-adducts observed upon in situ UVA photoexcitation of photocatalytic system P25/DMPO/glycerol under given experimental conditions (pH > 7). [ABSTRACT FROM AUTHOR]