Aerogel materials for photocatalytic detoxification of cyanide wastes in water

Ultraviolet-irradiated titania-silica (TiO2SiO2) aerogels were used as photocatalysts to oxidize/degrade aqueous cyanide species to CO2 and N2. TiO2SiO2 aerogel photocatalysts were prepared by the sol-gel technique and supercritical drying. Three types of TiO2SiO2 aerogel were prepared with different SiO2 contents (i.e., TiO2:SiO2 molar ratio = 1:1.3, 1:2.6 and 1:3.9). It was observed that, with increased SiO2 content, shrinkage and apparent density decreased and translucency increased. This resulted in higher photocatalytic activity for oxidation of CN− in dilute solutions (1000 and 522 ppm) of ferric cyanide. Compared with titania powder (i.e., anatase form with TiO2 > 98% and particle diameter < 1 μm), it was proven that the aerogel with highest SiO2 content (i.e. TiO2:SiO2 molar ratio = 1:3.9) had highest efficiency in the photocatalytic oxidation of CN− species under the same experimental conditions. This aerogel photocatalyst was filtered and re-used several times to check for activity loss; no significant change in the activity of the photocatalyst was observed.