Tang Hongxiao

Preparation and characterization of surface bond-conjugated TiO2/SiO2 and photocatalysis for azo dyes

Surface bond-conjugated TiO2/SiO2 was prepared by means of the impregnation method. Based on the results of XRD, FTIR, XPS and BET measurements, the growth of titania (predominantly anatase) on the silica substrate seems to occur by anchoring of the TiO2 phase through Ti-O-Si cross-linking bonds. The structure model of TiO2/SiO2 was proposed. Compared to B-TiO2, the most efficient catalyst is 30 wt.% TiO2/SiO2 (Ims30), which showed three times higher photoactivity for the degradation of reactive 15 (R15). In addition, the catalyst had a higher photoactivity on a silica of smaller particle size than on the silica of larger particles. Silica gel plays the basic role of dispersion and support for power TiO2. The isoelectric point of the catalyst was 3.0 pH units by the measurement of zeta-potential, indicating the presence of the surface acidity of the: catalyst. The photodegradation and the adsorption of R15 and cationic blue X-GRL (CBX) were investigated with the change of initial aqueous pH

Destruction of phenol aqueous solution by photocatalysis or direct photolysis

The photodegradation of phenol has been investigated under a high-pressure mercury lamp with a kind of jacket (glass or quartz) depending on used UV light range and a variety of experimental conditions: UV (lambda > 200 nm) with oxygen or with TiO2 and oxygen or with N2; UV (lambda > 330 nm) with oxygen or with TiO2 and oxygen or with N2. Photocatalysis and direct photolysis of phenol have different reaction pathways. Direct photolysis of phenol yielded a brown-yellow complex organic polymer in both aerobic and anaerobic environments. The polymer cannot be mineralized in an anaerobic environment. The effects of catalyst amount and oxygen concentration in the reaction atmosphere on the destruction of phenol were studied. The results prove that an appropriate catalyst amount can avoid direct photolysis and increase the mineralization rate of phenol.

Influence of adsorption on the photodegradation of various dyes using surface bond-conjugated TiO2/SiO2 photocatalyst

The adsorption and photodegradation have been investigated in illuminated surface bond-conjugated TiO2/SiO2 suspension for five commercial dyes, including cationic dyes, cationic blue X-GRL (CBX) and cationic pink FG (FG), and anionic reactive brilliant red K-2G (K-2G), reactive yellow KD-3G (KD-3G), and acid red B (ARB). Two adsorption modes are proposed. In the TiO2/SiO2 system, CBX and FG (FG) adsorbed on the catalyst surface by a penta-heterocycle N group, whereas, the other three anionic dyes adsorbed on the catalyst surface by a sulfonate group. The mode of adsorption of substrates to the TiO2/SiO2 particle surface is relevant factor to the formation of NH4+. The nitrogen of azo group was transformed to NH4+ ions and N-2 gas, and the penta-heterocycle and benzene-ring- su bsti Lute N groups in CBX and FG were transformed predominantly to NH4+ ions. The triazine ring and its substitute groups are much stable in the period of 8 h irradiation