Photocatalytic degradation of Cr(VI) using nano-sized TiO2

In this study, photocatalytic degradation of Cr(VI) employing aqueous TiO2 suspentions. Concentration of Cr(VI) ions were determined by standard spectrophotometric method (colored by carbazyde). Degradation studies were carried out at optimized catalyst mass and pH. The effect of contact period and dark adsorption on removal rate was also investigated. TiO2/UV system degraded 91% of Cr(VI) ions at 20 ppm initial concentration. To increase the removal ratio and degrease the light exposure time sacrifacing molecules EDTA or citric acid added to photocatalytic reaction medium. However, addition of EDTA inhibited the adsorption of the Cr(VI) ions on catalyst surface and reduced the degradation ratio. In the presence of citric acid, adsorbace on catalyst surface was highly prevented and photocatalytic removal of Cr(VI) ions slightly decreased. Additionally, Cr(VI) degradation was also investigated using nano-TiO2 immobilized into or onto biodegradable polymer polycaprolactone (PCL). Polymer studies were carried out at lower Cr(VI) concentrations. Degradation were quite good in the presence of 5% TiO2 (as the weight of PCL) immobilized into PCL and 1% TiO2 immobilized onto PCL surface at 5 ppm and 1,5 ppm Cr(VI) concentrations. Studies were also repeated using different light source (365 nm and 254 nm) and it was clear that degradation was more effective with 254 nm lamp. Degradation rate was higher in the presence of citric acid.Key Words: Photocatalytic decomposition, Titanium dioxide, Photocatalytic removal ofCr(VI)