Anti-oxidant/pro-oxidant activity of ascorbic acid Effect in the degradation of Acid Orange 7 with H2O2 catalyzed by transition metal ions

作者：Piumetti Marco; Freyria Francesca S; Armandi Marco; Saracco Guido; Garrone Edoardo; Bonelli Barbara^*

来源：Chimica Oggi-Chemistry Today, 2015, 33(3): 40-45.

• Heterogeneous catalysis
• Fenton mechanism
• liquid phase oxidation
• ascorbic acid
• titania
• azo-dyes

The effect of incubating mesoporous TiO2, with or without Fe3+ or V5+, in ascorbic acid (H(2)A) solutions before the catalytic oxidation in the dark with H2O2 of Acid Orange 7 was studied; the results were compared to the same reaction without H(2)A pretreatment. With a short incubation time, H(2)A irreversibly adsorbs on the TiO2 surface, depleting the related activity, so that pure TiO2 becomes inactive, and reduces surface ions to Fe2+ and V3+ species, so that the pristine reaction mechanisms (slow Fe3+-catalysed Fenton and stoichiometric oxidation by V5+ to V4+) are replaced by fast Fenton reactions. With long incubation times, H(2)A reacts with dissolved O-2 to form 2,3-diketo-L-gulono-delta-lactone and has a detrimental effect on the catalytic activity.

• 出版日期2015-6