Some problems including low treatment capacity,agglomeration and clogging phenomena,and short working life,limit the application of pre-treatment methods involving zero-valent iron （ZVI）.In this article,ZVI was froz...Some problems including low treatment capacity,agglomeration and clogging phenomena,and short working life,limit the application of pre-treatment methods involving zero-valent iron （ZVI）.In this article,ZVI was frozen in an amorphous state through a melt-spinning technique,and the decolorization effect of amorphous ZVI on Acid Orange II solution was investigated under varied conditions of experimental variables such as reaction temperature,ribbon dosage,and initial pH.Batch experiments suggested that the decolorization rate was enhanced with the increase of reaction temperature and ribbon dosage,but decreased with increasing initial solution pH.Kinetic analyses indicated that the decolorization process followed a first order exponential kinetic model,and the surface-normalized decolorization rate could reach 2.09 L/（m^2 ·min） at room temperature,which was about ten times larger than any previously reported under similar conditions.Recycling experiments also proved that the ribbons could be reused at least four times without obvious decay of decolorization rate and efficiency.This study suggests a tremendous application potential for amorphous ZVI in remediation of groundwater or wastewater contaminated with azo dyes.展开更多
Flake BiOBr was first prepared by a solution method at room temperature. Then, the produced BiOBr was calcined at different temperatures. It was found that BiOBr is not a stable compound. It transforms to plate-like B...Flake BiOBr was first prepared by a solution method at room temperature. Then, the produced BiOBr was calcined at different temperatures. It was found that BiOBr is not a stable compound. It transforms to plate-like Bi24031Brll at around 750 ℃ and the formed Bi24O31Br11 can further convert to rod-like a-Bi203 at around 850℃. The prepared compounds were characterized with X-ray diffraction （XRD）, N2 physical adsorption, scanning electron microscopy （SEM）, and UV-Vis diffuse reflectance spectra （DRS）, respectively. The photocatalytic activity of the produced bismuth oxybromides was evaluated by photocatalytic decomposition of acid orange Ⅱ under both visible light （λ〉420 nm） and UV light （λ=365 nm） irradiation. Results show that these compounds have different band gaps and different photocatalytic properties. The band gap energies of the as-prepared samples were found to be 2.82, 2.79, 2.60 and 3.15 eV for BiOBr, BiOBr/Bi24O31Br, Bi24O31Br, and a-Bi2O3, respectively. Under both UV light and visible light irradiation, the photocatalytic activity follows the order： BiOBr/Bi24O31Br mixture 〉 BiOBr 〉 Bi24031Br〉a-Bi2O3. The change in photocatalytic activity could be attributed to the different light absorption ability and microstructures of the photocatalysts.展开更多
Electrochemically assisted photocatalysis is an effective approach to improve photocatalytic efficiency. In this paper, modified β-PbO2 electrode was prepared by TiO2 co-deposition and characterized by SEM and XRD. T...Electrochemically assisted photocatalysis is an effective approach to improve photocatalytic efficiency. In this paper, modified β-PbO2 electrode was prepared by TiO2 co-deposition and characterized by SEM and XRD. Then 2.0 g TiO2 modified β-PbO2 electrode (2.0 g TiO2 involved in the 200 mL co-deposition solution) was used in electrochemically assisted photocatalytic degradation of Acid Orange II and the influence of initial pH values was investigated when the potential applied across the electrodes was 1.5 V. When the potential applied was 2.5 V, the difference of the degradation process and the final products were studied. The results indicated that 2.0 g TiO2 modified β-PbO2 electrode was different from the unmodified one in that the β-PbO2 crystals became finer and the electrode became more compact and more uniform. The synergetic effect in electrochemically assisted photocatalytic degradation of Acid Orange II was observed and degradation efficiency and TOC removal were the highest at initial solution pH 2.0. By UV-visible spectral analysis, it was proved that photoelectrochemical synergetic degradation of Acid Orange II went through the step of producing main product maleic acid for the solution at the initial pH 2.0 within 2 h, but the degradation was slow for the solution at the initial pH 12.0.展开更多
The TiO 2 nanotube sample was prepared via a NaOH solution in a Teflon vessel at 150℃. The as-prepared nanotubes were then treated with H 2SO 4 solutions. The TiO 2 nanotube has a crystalline structure with open-...The TiO 2 nanotube sample was prepared via a NaOH solution in a Teflon vessel at 150℃. The as-prepared nanotubes were then treated with H 2SO 4 solutions. The TiO 2 nanotube has a crystalline structure with open-ended and multiwall morphologies. The TiO 2 nanotubes before and after surface acid treatment were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and UV-VIS dispersive energy spectrophotometry(DRS). The photocatalytic activity of the samples was evaluated by photocatalytic degradation of acid orange II in aqueous solutions. It was found that the order of photocatalytic activity was as follows: TiO 2 nanotubes treated with 1.0 mol/L H 2SO 4 solution (TiO 2(1.0M H 2SO 4) nanotubes)>TiO 2 nanotubes treated with 0.2 mol/L H 2SO 4 solution (TiO 2(0.2M H 2SO 4) nanotubes)>TiO 2 nanotubes >TiO 2 powder. This was attributed to the fact that TiO 2 nanotubes treated with H 2SO 4 was composed of smaller particles and had higher specific surface areas. Furthermore, the smaller TiO 2 particles were beneficial to the transfer and separation of photo-generated electrons and holes in the inner of and on the surface of TiO 2 particles and reduced the recombination of photo-generated electrons and holes. Acid treatment was particularly effective for TiO 2 nanotubes, this increase in activity was correlated with the concentration of H 2SO 4 solution.展开更多
基金the financial support from the Ministry of Science and Technology of China(No. 2011CB606301)the National Natural Science Foundation of China (No. 50825402,51101156)
文摘Some problems including low treatment capacity,agglomeration and clogging phenomena,and short working life,limit the application of pre-treatment methods involving zero-valent iron （ZVI）.In this article,ZVI was frozen in an amorphous state through a melt-spinning technique,and the decolorization effect of amorphous ZVI on Acid Orange II solution was investigated under varied conditions of experimental variables such as reaction temperature,ribbon dosage,and initial pH.Batch experiments suggested that the decolorization rate was enhanced with the increase of reaction temperature and ribbon dosage,but decreased with increasing initial solution pH.Kinetic analyses indicated that the decolorization process followed a first order exponential kinetic model,and the surface-normalized decolorization rate could reach 2.09 L/（m^2 ·min） at room temperature,which was about ten times larger than any previously reported under similar conditions.Recycling experiments also proved that the ribbons could be reused at least four times without obvious decay of decolorization rate and efficiency.This study suggests a tremendous application potential for amorphous ZVI in remediation of groundwater or wastewater contaminated with azo dyes.
文摘Flake BiOBr was first prepared by a solution method at room temperature. Then, the produced BiOBr was calcined at different temperatures. It was found that BiOBr is not a stable compound. It transforms to plate-like Bi24031Brll at around 750 ℃ and the formed Bi24O31Br11 can further convert to rod-like a-Bi203 at around 850℃. The prepared compounds were characterized with X-ray diffraction （XRD）, N2 physical adsorption, scanning electron microscopy （SEM）, and UV-Vis diffuse reflectance spectra （DRS）, respectively. The photocatalytic activity of the produced bismuth oxybromides was evaluated by photocatalytic decomposition of acid orange Ⅱ under both visible light （λ〉420 nm） and UV light （λ=365 nm） irradiation. Results show that these compounds have different band gaps and different photocatalytic properties. The band gap energies of the as-prepared samples were found to be 2.82, 2.79, 2.60 and 3.15 eV for BiOBr, BiOBr/Bi24O31Br, Bi24O31Br, and a-Bi2O3, respectively. Under both UV light and visible light irradiation, the photocatalytic activity follows the order： BiOBr/Bi24O31Br mixture 〉 BiOBr 〉 Bi24031Br〉a-Bi2O3. The change in photocatalytic activity could be attributed to the different light absorption ability and microstructures of the photocatalysts.
文摘Electrochemically assisted photocatalysis is an effective approach to improve photocatalytic efficiency. In this paper, modified β-PbO2 electrode was prepared by TiO2 co-deposition and characterized by SEM and XRD. Then 2.0 g TiO2 modified β-PbO2 electrode (2.0 g TiO2 involved in the 200 mL co-deposition solution) was used in electrochemically assisted photocatalytic degradation of Acid Orange II and the influence of initial pH values was investigated when the potential applied across the electrodes was 1.5 V. When the potential applied was 2.5 V, the difference of the degradation process and the final products were studied. The results indicated that 2.0 g TiO2 modified β-PbO2 electrode was different from the unmodified one in that the β-PbO2 crystals became finer and the electrode became more compact and more uniform. The synergetic effect in electrochemically assisted photocatalytic degradation of Acid Orange II was observed and degradation efficiency and TOC removal were the highest at initial solution pH 2.0. By UV-visible spectral analysis, it was proved that photoelectrochemical synergetic degradation of Acid Orange II went through the step of producing main product maleic acid for the solution at the initial pH 2.0 within 2 h, but the degradation was slow for the solution at the initial pH 12.0.
文摘The TiO 2 nanotube sample was prepared via a NaOH solution in a Teflon vessel at 150℃. The as-prepared nanotubes were then treated with H 2SO 4 solutions. The TiO 2 nanotube has a crystalline structure with open-ended and multiwall morphologies. The TiO 2 nanotubes before and after surface acid treatment were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and UV-VIS dispersive energy spectrophotometry(DRS). The photocatalytic activity of the samples was evaluated by photocatalytic degradation of acid orange II in aqueous solutions. It was found that the order of photocatalytic activity was as follows: TiO 2 nanotubes treated with 1.0 mol/L H 2SO 4 solution (TiO 2(1.0M H 2SO 4) nanotubes)>TiO 2 nanotubes treated with 0.2 mol/L H 2SO 4 solution (TiO 2(0.2M H 2SO 4) nanotubes)>TiO 2 nanotubes >TiO 2 powder. This was attributed to the fact that TiO 2 nanotubes treated with H 2SO 4 was composed of smaller particles and had higher specific surface areas. Furthermore, the smaller TiO 2 particles were beneficial to the transfer and separation of photo-generated electrons and holes in the inner of and on the surface of TiO 2 particles and reduced the recombination of photo-generated electrons and holes. Acid treatment was particularly effective for TiO 2 nanotubes, this increase in activity was correlated with the concentration of H 2SO 4 solution.
