Degradation of organic compounds using nanosized titania

Five titania with different phases (rutile (M1), anatase (M2, T1, T2, and N1)), average crystallite sizes (M1: 9[is an empty set]x45, M2: 11, T1: 26, T2: 6, and N1: 37 and 14[is an empty set]x110 nm) and specific surface areas (50-250 sq.m/g) were investigated in this work. To confirm their physical properties reported by manufacturers, TEM, XRD, and BET techniques were used and the obtained results agreed well with the reported values. To examine decomposition performance, each titania was dispersed in three different simulated wastewater contaminating: methylene blue (10, 20 ppm), black 5 (10, 20 ppm), and lignin (10, 20 ppm). Adsorption of each pollutant on the 5 titania was investigated in the absence of illumination. Based on experimental results on methylene blue removal, M1 was found to exhibit the best adsorption efficiency of 34.2%. However, T1 provided the best decomposition efficiency of 88.1% with irradiation by two 30-Watt UV lamps. As for the wastewater with black 5, none of the titania exhibited any significant adsorption. Nevertheless, with irradiation by UV light, T1 again exhibited the best decomposition efficiency of 92.5%. Similarly, it was found that lignin could not be adsorbed by any of the 5 titania. As expected, T1 could again provide the best lignin removal performance with maximum efficiency of 96.8%. These results could be attributed to the fact that T1 is anatase titania with quite high specific surface area. Sunlight also used for activating the 5 titania. The total removal efficiency obtained by sunlight of T2-titania was higher because sunlight source had the suitable spectrum. Finally, in order to avoid losing nanosize titania with the treated wastewater, application of titania thin layer depositing on glass microfibre filter (Whatman, GF/A) was employed. However, the efficiency of black 5 decomposition was drastically decreased to only 6%