Weiyun Shao

Effect of calcination temperature on the catalytic activity of nanosized TiO2 for ozonation of trace 4-chloronitrobenzene

Nanosized titanium dioxides were synthesized by hydrolysis of TiCl(4) followed by calcination at different temperatures ranging from 300 to 1,000 °C. The as-prepared samples were characterized by X-ray diffraction, N(2) adsorption-desorption, and zeta potential analysis. The catalytic activities of the TiO(2) nanoparticles were tested by catalytic ozonation of trace 4-chloronitrobenzene (4-CNB) in water. Moreover, the catalytic ozonation activity of a sample calcined at 400 °C (denoted as T400) was tested in aqueous solution using electron paramagnetic resonance (EPR) spin trapping technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trap. It was found that with increasing calcination temperatures, the average crystallite size and average pore size increased, in contrast the BET surface areas decreased. However, the isoelectric point (IEP) first increased, and then decreased. The ozone adsorption on the catalyst surface played an important role in determining their catalytic activity. Sample T400 with the IEP of 7.0, farthest away from the 4-CNB solution pH value (pH = 5.3), showed the best catalytic activity. The EPR experiments further confirmed that the hydroxyl radicals TiO(2)-catalyzed ozonation followed a radical-type mechanism.

Hydrothermal synthesis of hydrangea-like F-doped titania microspheres for the photocatalytic degradation of carbamazepine under UV and visible light irradiation

Hydrangea-like F-doped TiO2 microspheres have been synthesized on a large scale by a simple hydrothermal process using potassium titanium oxalate as the titanium source, ammonium fluoride and hydrogen peroxide as the etchant. The photocatalytic activities were evaluated using carbamazepine as the target organic molecule under UV and visible light irradiation. Structural characterization indicates that the hydrangea-like TiO2 microspheres, with an average diameter of 2.80 µm, are composed of numerous anatase TiO2 petals. Moreover, it is found that both the NH4F and H2O2 dosages have important effects on the formation of the hydrangea-like structures. In addition, photocatalytic experiments show that the hydrangea-like TiO2 microspheres calcined at 500°C exhibit high photocatalytic efficiency under both UV and visible light irradiation. The enhanced photocatalytic activity can be attributed to the successful fluorine doping, good crystallinity, and the unique nanostructures.

Hydraulic Features of Air-Water Mixture Flow on a Staircase with Rest Platforms

AbstractTo investigate hydraulic features of the flooding flow on a staircase with a rest platform, experiments were conducted on a 1:2-scale physical model of a staircase with a middle rest platform between two stair segments. The transition or skimming flow occurring on the first segment is similar to that on a stepped chute. However, a jet flow forms immediately downstream of the rest platform, followed by a redeveloping transition flow on the second segment. The measured profiles of air concentrations in those flow regions agree well with that in the skimming and transition flow known from stepped spillways. The amount of air entrained into the free-falling jet increases dramatically because of a higher air concentration in the approaching flow. Rapid rises of the air-water mixture depth and the flow velocity in part of the jet and the transition flow downstream were observed. These features could affect human maneuverability on a flooding staircase with rest platform(s) and make it more difficult for...