Photocatalytically decomposition

Kinetic analysis based on the Langmuir-Hinshelwood model was performed on the assumption that ethylene and water vapor molecules were adsorbed on the same active site competitively [2]. We assumed then that overall photocatalytic decomposition rate was controlled by the surface reaction of adsorbed ethylene. Under the water vapor concentration from 10,200 to 28,300ppm, and the ethylene concentration from 30 to 100 ppm, the reaction rate equation can be represented by Eq.(l), based on the fitting procedure of 1/r vs. 1/ Ccm ... 

The photocatalytic decomposition of 4-NP can be written in terms of Langmuir-Hishelwood (L-H) kinetics [3]. 

From plotting of 1/r versus 1/C, the reaction rate constant, k and adsorption constant, K can be obtained. Fig. 3 indicates that photocatalytic decomposition of 4-NP is in good agreement with L-H model. In the present work, the values of k and K in the presence of H2O2 were found to be higher than those in the absence of H2O2, as shown in Table 1. 

Fig. 2. Effect of HjOj (5mmol/L) on the photocatalytic decomposition of 4-NP (Co=25ppm) over Ti02/Cr-Ti-MCM-41 in visible light.

The photocatalytic decomposition of TCE was carried out and the results were shown in Fig. 3. Photocatalytic reaction has been found to be less sensitive to the conditions such as the concentration of trichloroethylene, and the stoichiometric decomposition (Cl2C=CHCl + 3/2O2 + H2O 2CO2+ 3HC1) proceeds with fairly good reproducibility by prepared photocatalysts. 

Fig. 3. Catalytic performance of modified P-25 catalysts and prepared Ti02 catalysts for photocatalytic decomposition of TCE (O.lg/L)...

In this study Ti02 was coated mainly at the exterior surface of granular activated carbon, and this Ti02-coated activated carbon was employed for the adsorption followed by photocatalytic decomposition of TCE. 

Application of fluidized reactor in photocatalytic decomposition of gaseous acetic acid and ammonia... 

In our experiment, photocatalytic decomposition of ethylene was utilized to probe the surface defect. Photocatalytic properties of all titania samples are shown in table 2. From these results, conversions of ethylene at 5 min and 3 hr were apparently constant (not different in order) due to the equilibrium between the adsorption of gaseous (i.e. ethylene and/or O2) on the titania surface and the consumption of surface species. Moreover it can be concluded that photoactivity of titania increased with increasing of Ti site present in titania surface. It was found that surface area of titania did not control photoactivity of TiOa, but it was the surface defect in titania surface. Although, the lattice oxygen ions are active site of this photocatalytic reaction since it is the site for trapping holes [4], this work showed that the presence of oxygen vacancy site (Ti site) on surface titania can enhance activity of photocatdyst, too. It revealed that oxygen vacancy can increase the life time of separated electron-hole pairs. 

The oxidative degradation of organic pollutants in water and air streams is considered as one of the so-called advanced oxidation processes. Photocatalytic decomposition of organics found widespread industrial interest for air purification (e.g., decomposition of aldehydes, removal of NO , ), deodorization, sterilization, and disinfection. Domestic applications based on Ti02 photocatalysts such as window self-cleaning, bathroom paints that work under illumination with room light, or filters for air conditioners operating under UV lamp illumination have already been commercialized. Literature-based information on the multidisciplinary field of photocatalytic anti-pollutant systems can be found in a number of publications, such as Bahnemann s [237, 238] (and references therein). 

In situ metallization has been claimed to provide a convenient method for the preparation of metal-deposited and metal sulfide deposited CdS during photocatalytic decomposition of aqueous sulfide. As-prepared MS/CdS and M/CdS bifunctional photocatalysts (MS = Pt or Ir sulfide M = Pt or Ir) were reported to be more active photocatalysts than CdS and ex-situ metallized CdS [285]. 

The photocatalytic decomposition of water was carried out in a closed gas circulation system connected to a high-vacuum line. About 200 mg of a powdered catalyst was dispersed in pure distilled water and irradiated through a water filter with an Xe lamp operated at 400 W. Hydrogen and oxygen evolved in the gas phase were analyzed by a gas chromatograph which was directly connected to the reaction system. 

Sakatani Y, Nunoshige J, Ando H, Okusako K, Koike H, Takata T, Kondo JN, Hara M, Domen K (2003) Photocatalytic decomposition of acetaldhyde under visible light irradiation overLa3+ and N Co-doped Ti02. Chem Lett 32(12) 1156-1157... 

Effect of ultrasound on the photocatalytic decomposition of KI using Ti02 doped with rare earths. 

When ethanol was used to extract the dye, the efficiency increased to 0.71% the rationale is the higher solubility of the sensitizer in alcohol and minor association which favors a more homogeneous distribution of the anthocyanins on the Ti02 surface. However, exposure to simulated sunlight (AM = 1.5,100 mWcm 2) caused a significant decrease in efficiency after 3h, probably because alcohol favors the photocatalytic decomposition of anthocyanin. 

Domen, K., Kudo, A., Onishi, T., Kosugi, N., and Kuroda, H., Photocatalytic decomposition of water into hydrogen and oxygen over nickel (II) oxide-strontium titanate (SrTiOj) powder. 1. Structure of the catalysts, ]. Phys. Chem., 90, 292,1986. 

Sayama, K. and Arakawa, H., Effect of carbonate salt addition on the photocatalytic decomposition of liquid water over PtTiOz catalyst, /. Chem. Soc., Faraday Trans., 93,1647,1997. 

Gruzdkov, Yu.A., Savinov, E.N., and Parmon, V.N., Photocatalytic decomposition of hydrogen sulfide in the presence of polymer immobilized cadmium sulfide. Promotion by I and VIII group metals, Int.. Hydrogen Energ., 12, 393, 1987. 

Usually, the most typical processes that are covered by photocatalysis are the photocatalytic oxidation (PCO) and the photocatalytic decomposition (PCD) of substrates, which most often belong to the organic class of compounds. The former process employs the use of gas-phase oxygen as direct participant to the reaction, while the latter takes place in the absence of Oz. 

The photocatalytic decomposition products of methyl orange were separated by RP-HPLC and identified by MS, MS/MS techniques. Methyl orange was irradiated in the presence of Ti02 dispersions. Samples were taken after various incubation times, filtered... 

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