[Study on photocatalytic degradation of 1, 2, 3-trichlorobenzene using the microwaved MWNTs/TiO2 composite].

Composite photocatalyst, MWNTs/TiO2, is prepared using sol-gel method and dried through microwave irradiation. Characterization of the composite shows that, with the increase of microwave power till 400 W, the average diameter of MWNTs/TiO2 composite reduces gradually, and better dispersion of the composites is also acquired at the microwave power of 400 W. However, a further increase of the power results in the average diameter of the composite enlarged, and more aggregative composites are obtained. Furthermore, photodegradation of 1,2,3-trichlorobenzene (1,2,3-TCB) with the composite photocatalysts of MWNTs/TiO2 induced under different microwave conditions is studied. It is found that the photodegradation of 1,2,3-TCB follows the first-order kinetics. The microwaving conditions for producing the composite photocatalysts with the highest photocatalytic activity are further determined as 5 min irradiation at 400 W. Under such conditions, the rate constant of 1,2,3-TCB photodegradation is 0.023 7 min(-1) which is elevated by 52% comparing to those obtained using non-microwaved composites.

[Photocatalytic degradation of 1,2, 4-trichlorobenzene with TiO2 coated on carbon nanotubes].

Effects and kinetics of photocatalytic degradation of 1,2,4-trichlorobenzene with composite photocatalysts of TiO2 coated on carbon nanotubes and nano-TiO2 photocatalysts were studied, respectively. It was found that the composite photocatalysts was better than the nano-TiO2 for photocatalytic degradation of 1,2,4-trichlorobenzene. After 60 min UV irradiation at 254 nm, there was 70% of the initial 1,2,4-trichlorobenzene degraded with the composite photocatalyst while only 51% of the initial 1,2,4-trichlorobenzene degraded with the nano-TiO2. Results of photocatalytic degradation kinetics also proved that the 1,2,4-trichlorobenzene degradation rate constant with the composite photocatalyst was 0.019 6 h(-1), which was increased by 63.3% compared to that with nano-TiO2. According to molecular structure theory, analysis of dissociation energy of C--Cl bond of chlorobenzenes predicated that main pathway of photocatalytic degradation of 1,2,4-trichlorobenzene followed that its ortho-Cl could be took off first to form 1, 4-dichlorobenzene, and it might be further dechlorized and finally be mineralized. The first step of photodechlorination for 1,2,4-trichlorobenzene was also experimentally confirmed through identified 1,4-dichlorobenzene as its product.