Catalytic degradation of Acid Orange 7 by H2O2as promoted by either bare or V-loaded titania under UV light, in dark conditions, and after incubating the catalysts in ascorbic acid

Marco Piumetti,Barbara Bonelli,Guido Saracco,Marco Armandi,Edoardo Garrone,Francesca S Freyria,Giovanny Esteban Gonzalez

doi:10.1080/2055074x.2015.1105618

Abstract

AbstractPure and V-loaded mesoporous titania (with 2.5 wt-% V) were prepared by template-assisted synthesis and compared to commercial titania (Degussa P25), both as such and after vanadium loading. Mesoporous TiO2 occurred as pure anatase nanoparticles with higher surface area (SSA = 150 m2 g−1) than P25 (SSA = 56 m2 g−1).Degradation of the azo dye Acid Orange 7 by H2O2 was used as a test reaction: under UV light, no difference emerged between mesoporous TiO2 and P25, whereas in dark conditions, higher SSA of the mesoporous sample resulted in higher conversions. Under UV illumination, surface V5+ species inhibited photocatalytic activity, by forming inactive V4+ species. Similarly, in dark conditions, V5+ surface species reacted with H2O2, likely yielding ·O2H radicals and reducing to V4+. On the contrary, V-containing catalysts were very active after pretreatment with ascorbic acid, which reduced V5+ species to V3+species, the latter promoting very lively a Fenton-like reaction.

Highlights

Degradation of the azo dye Acid Orange 7 by H2O2 was used as a test reaction: under UV light, no difference emerged between mesoporous TiO2 and P25, whereas in dark conditions, higher specific surface area (SSA) of the mesoporous sample resulted in higher conversions
One current application of TiO2 is the degradation of organic pollutants, including azo dyes,[4] a class of organic molecules widely applied in the photographic industry,[13] which can be removed by photocatalytic degradation with TiO2, usually in the presence of an oxidizing agent, like H2O2.2
Results obtained under UV light with 0.030 M H2O2 are reported in Fig. 4: as expected, addition of H2O2 to the reaction mixture had a positive effect on the photocatalytic activity of all the samples

Summary

Introduction

Degradation of the azo dye Acid Orange 7 by H2O2 was used as a test reaction: under UV light, no difference emerged between mesoporous TiO2 and P25, whereas in dark conditions, higher SSA of the mesoporous sample resulted in higher conversions.

Results

Conclusion