Zili Xu

The preparation and characterization of ZnO ultrafine particles

Abstract In this paper, ZnO ultrafine particles (UFPs) were prepared by the thermal decomposition method of the precursor, zinc carbonate hydroxide. The structure and properties of the as-prepared ZnO UFPs were studied using TEM, XRD, BET, SPS, ESR, Raman, XPS and UV–Vis absorption spectroscopy. It was found that the prepared ZnO UFPs exhibited obvious quantum size effect and surface effect. In addition, there were many active species on the surface of ZnO UFPs such as oxygen deficiencies and hydroxyls, both of which can improve the photocatalytic activities of ZnO UFPs.

Analyses of volatile organic compounds concentrations and variation trends in the air of Changchun, the northeast of China

Abstract The concentrations of volatile organic compounds (VOCs) were monitored from September 1997 to July 1998 at five different function zones in Changchun, the northeast of China. The VOCs levels by the roadside (the center zone of the main street) and in the downtown area were higher than those in other three areas, with the lowest concentration observed at rural site. A seasonal variation of VOCs in all sampling sites was observed, with the maximum in winter and the minimum in spring. The diurnal variation of the total mean VOC concentrations showed two peaks related with traffic density for the A, B and D sites, and a single peak for the industrial area.

Photocatalytic oxidation of heptane in the gas-phase over TiO2.

In this paper, gas-phase photocatalytic oxidation (PCO) of heptane over UV-illuminated TiO2 was carried out at ambient temperature in a batch reactor. Complete oxidation of heptane with almost stoichiometric production of CO2 and H2O was observed. The intermediates detected were propanal, butanal, 3-heptanone, 4-heptanone and carbon monoxide. A scheme of the possible mechanism for PCO of heptane over TiO2 was suggested. Langmuir-Hinshelwood kinetics equation was obtained from the results at different initial concentrations of heptane, oxygen, moisture and light intensity. The photocatalytic activity of TiO2 can be sustained indefinitely. This can be attributed to the production of water in the system, which can replenish the consumed hydroxyl radicals.

The preparation and characterization of TiO2 ultrafine particles

Ultrafine particles (UFP) were prepared by means of the colloidal chemical method. The structure and properties of the as-prepared TiO2 UFP, having been submitted to different heat-treatment tests, were studied using TEM, XRD, IR, SPS, Raman, XPS and UV–vis absorption spectrum. The results of the XPS, SPS and UV–vis absorption spectrum indicated that on the surface of TiO2 UFP, there were surface active species such as Ti3+ and hydroxyl which can improve the photocatalytic activity of TiO2 UFP.

Kinetics of gas-phase photocatalytic oxidation of heptane over TiO2

In this paper, gas-phase photocatalytic oxidation of heptane over UV-illuminated TiO2 was carried out in a batch reactor. A Langmuir-Hinshelwood kinetic equation was observed from the results at different initial concentrations of heptane, oxygen, water vapor, and light intensity.