Degradation of azo dyes in aqueous TiO2 suspensions employing UV and visible radiation.

SATUF, M. L.; PIERRESTEGUI, M. J.; BRANDI, R. J.; ALFANO, O. M.

San Pablo, Brasil

Otro; V Encuentro sobre Aplicaciones Ambientales de Procesos Oxidativos Avanzados (V EPOA); 2009

Universidad de San Pablo

Azo dyes present in wastewaters from the textile industry constitute a major threat to the environment due to their toxicity, non-biodegradability and potentially carcinogenic nature. Heterogeneous photocatalysis with titanium dioxide (TiO2) has been proposed as an effective method to degrade this kind of pollutants. The degradation mechanism of the dye depends on the wavelength of irradiation. Radiation in the UV range can induce charge separation in the TiO2 particle. On the other hand, under visible light, initial excitation of dye molecules occurs. Electrons are then injected from the excited states of the dye into the conduction band of the semiconductor. Charges present in the TiO2 particle, generated by either mechanism, can migrate to the semiconductor surface and react with adsorbed molecules and ions (O2, OH–, H2O) to generate reactive oxygen species, such as ·OH, which can attack dye molecules and lead to their degradation. The objectives of this work are: (i) Study of the degradation of the azo dye Acid Orange 7 (AO7) employing TiO2 Degussa P25 and UV-visible radiation. (ii) Efficiency analysis of photocatalysis (UV range) and photosensitization (visible range).