Experimental Study of Influencing Factors and Kinetics in Catalytic Removal of Methylene Blue with TiO2 Nanopowder
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In this research, degradation of methylene blue as a dye pollutant was investigated in the presence of TiO2 nanopowders using photolysis and sonolysis systems separately and simultaneously. Effect of different parameters such as catalyst dosage, initial concentration of dye, UV power, pH and type of catalyst on the removal efficiency was ascertained. The results showed that basic pH is proper for the photocatalytic removal of the dye. Furthermore higher UV power and lower initial concentration of dye leads to higher removal percent. Moreover TiO2 showed more photocatalytic activity than ZnO in the nanopowder form. The experimental kinetic data followed the pseudo-first order model in both photocatlytic and sonophotocatalytic processes but the rate constant of sonophotocatalysis is higher than it at photocatalysis process. Finally the reaction order of the rate law respect to nanocatalyst dosage in photocatalysis process is obtained 1.45. High activation energy of this process shows its high sensitivity to temperature.Keywords:
Methylene blue
Degradation
Methyl orange
Zinc nitrate
p–n junction
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This study prepared TiO2 film photocatalyst based on Ti plate using sol-gel method. XRD result demonstrated that the prepared photocatalyst mainly consisted of anatase crystals about 35.7nm on the average. SEM characterization result showed that the surface of the photocatalyst was very even and compact. And TiO2connected with the Ti plate closely and firmly. The photoelectrochemistry characteristic of the photocatalyst tested with electrochemistry method indicated that the prepared photocatalyst was n-type semiconductor and the extra electric field would promote the separation of photogenerated electron and hole in favor of the increase of the photocatalysis efficiency. The degradation experiments of benzamide by photocatalysis and electrically assisted photocatalysis (EAP) demonstrated that the extra electric field had the obvious assistant effect on photocatalysis and the benzamide degradation rate by EAP was much higher than that by photocatalysis. When the electrode potential of photocatalyst was -0.05V/SCE,the removal efficiency of benzamide could be 95% in 120min.
Benzamide
Degradation
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Redistribution
Settling
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Fe3+ and Al 3+ co-doped TiO2(Fe3+/Al3+-TiO2)composite photocatalysts were prepared by the sol-gel method using Ti(OC4H9)4 as precursor and characterized by X-ray diffraction(XRD)and UV-Vis.The effect of calcination temperature and salts in photocatalytic system on the photocatalytic activity of Fe3+/Al3+-TiO2 were investigated by photocatalytic degradation of methyl orange irradiated by sunlight.The photocatalytic activity of Fe3+/Al3+-TiO2 was enhanced with increasing temperature.HCO3-and NO2-decreased its photocatalytic activity.
Methyl orange
Degradation
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Photocatalysis has been widely applied in various areas, such as solar cells, water splitting, and pollutant degradation. Therefore, the photochemical mechanisms and basic principles of photocatalysis, especially TiO2 photocatalysis, have been extensively investigated by various surface science methods in the last decade, aiming to provide important information for TiO2 photocatalysis under real environmental conditions. Recent progress that provides fundamental insights into TiO2 photocatalysis at a molecular level is highlighted. Insights into the structures of TiO2 and the basic principles of TiO2 photocatalysis are discussed first, which provides the basic concepts of TiO2 photocatalysis. Following this, details of the photochemistry of three important molecules (oxygen, water, methanol) on the model TiO2 surfaces are presented, in an attempt to unravel the relationship between charge/energy transfer and bond breaking/forming in TiO2 photocatalysis. Lastly, challenges and opportunities of the mechanistic studies of TiO2 photocatalysis at the molecular level are discussed briefly, as well as possible photocatalysis models.
Photocatalytic water splitting
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Underlayer exposed ZnO:Al-TiO2 coupled films are prepared by different means.Surface morphology by SEM,microstructure by XRD,film thickness by surface profiler and photocatalysis are investigated.In order to explain the enhanced photocatalysis,reaction Ag++→Ag↓ is adopted to clarify the mechanism.It turns out that during the process of photocatalysis the exposed part of the underlayer releases e-and this suppresses recombination of light-induced charges,thus enhanced photocatalysis.
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A kind of magnetically separable visible-light photocatalyst BiVO4/Fe3O4 was prepared by ultrasonic method and BiVO4 supported on magnetite particles to enable recovery after photocatalytic degradation.The physical and photocatalytic performances of as-synthesized products were characterized by X-ray diffraction(XRD) and transmission electron microscope(TEM).The photocatalytic degradation of methylene blue(MB) was studied including the effects of photocatalyst dosage,initial concentration,pH value and the existence of electron acceptors on photocatalytic degradation.The results indicated that after 5 h,the methylene blue was degradated under the conditions of initial concentration 10mg/L,BiVO4/Fe3O4 concentration was 2.0g/ml,pH value was 11 and the existence of K2S2O8.The photocatalyst can be recycled with a little decreasing of photocatalytic activity,and the degradation rate of methylene blue was still higher than 80% after three cycles.
Methylene blue
Degradation
Visible spectrum
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Methylene blue
Methylene
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