Advanced Materials Research Vols. 197-198

Abstract: TiO₂ can be used as a photocatalyst because of its semiconductor property. When TiO₂ is doped with transition metal ions, its electronic properties may be modified. In this work, nanosized Sn⁴⁺-doped TiO₂ (TiO₂-Sn⁴⁺) particles have been synthesized by a sol-gel process at different temperature. Their microstructure and crystal structure depending on the calcination temperatures were investigated using XRD and SEM techniques. The photocatalytic degradation of diesel pollutants in seawater was investigated by using Sn⁴⁺-doped nanometer TiO₂ under UV irradiation. In the experiment, the effect of different ratio of Sn⁴⁺ doped into TiO₂, the effect of calcination temperature of Sn-doped nano-TiO₂, the effect of Sn⁴⁺-doped nanometer TiO₂ dosage, pH value and photocatalytic degradation reaction time, respectively, on the removal of diesel pollutants in seawater was investigated. On the basis of the results of these experimental data, the optimal experimental conditions for photocatalytic degradation of diesel are tried through the orthogonal test. The results reveal that when the ratio of Sn⁴⁺ doped into TiO₂ was 3% wt, the calcination temperature of Sn-doped nano-TiO₂ was 400°C, the Sn⁴⁺-doped nanometer TiO₂ dosage was 1 g/L, pH value was 8 and photocatalytic degradation reaction time was 1.5h, respectively, the removal rate of diesel pollutants in seawater was expected to reach 88.00 %.

Abstract: TiO₂ nanotubes were synthesized using TiO₂ powder as raw material from a hydrothermal method. It was observed that the sample prepared at 130°C and calcined at 450°C only anatase formed, but the sample calcined at 800°C, both anatase and rutile formed. The obtained TiO₂ nanotubes prepared at a hydrothermal temperature of 130°C and calcined at 450°C have a greater surface area of 356.8m²/g. Moreover, the TiO₂ nanotubes demonstrate the photocatalytic degradation of methylene blue solution effectively by exposing the nanotubes in aqueous solution under visible light.

Abstract: TiO₂ pillared rectorite (TPLR) had been synthesized by sol-gel method, and was characterized by XRD, TEM, BET, UV-vis DRS and FTIR. The effects of calcination temperature on the microstructure and the photocatalytic activity of the as prepared catalyst were investigated. The photocatalytic activity of the catalyst was evaluated by decomposition of Acid Red B (ARB) aqueous solution. XRD patterns revealed that TiO₂ is incorporated into the interlayer of the rectorite. TEM demonstrated that TiO₂ particles are present in the rectorite. The BET analysis indicated that the surface area of the sample calcined at 300°C (TPLR-300) was larger than those of other samples. The TPLR samples had high adsorption capacity and good photocatalytic efficiency in decomposition of ARB in water. FTIR spectra of the original and the recovered samples indicated that the catalyst had not chemically changed during the photocatalytic reaction.

Abstract: In this paper, we have studied the photocatalytic activity of TiO₂ which was modified by ferric stearate; ferrocene and nickel N,N-dibuty dithiocarbamate (NiDBC) , respectively. Innovatively, methylene blue (MB) was used as model pollutant. Under visible light irradiation, this paper studied the effect of the photocatalytic degradation of MB. The result shows that when the mass ratio is 5:1, the catalytic effect is C>B>A. When mass ratio is 1:1, the catalytic effect is B>C>A. Another result shows that with the increase of the amount TiO₂, catalytic effect of TiO₂ modified by ferric stearate significantly increases, otherwise, TiO₂ modified by ferrocene and NiDBC were different.

Abstract: In this paper, electrolysis and hypochlorite oxidation methods are adopted for the preparation of potassium ferrate, focusing on increasing the production yield and product’s purity. The oxidation of benzopyrene by potassium ferrate was investigated. The yield of potassium ferrate prepared with hypochlorite at optimized conditions is 21% higher than that of using electrolysis method. With the presence of hypochlorite, various conditions of oxidation reaction were determined as following: reaction temperature 25°C, re-crystallization temperature of -5 °Cand reaction time 40 minutes, which all contribute a yield of 80%. Spectrophotometric was used to analyze the purity of the product, which was measured up to 97%. XRD and IR were used to characterize the final product. The aqueous stability of potassium ferrate at various pH values was investigated. It was found that potassium ferrate solution had a maximum stability at pH 9-10.5. With three-dimensional excitation emission matrix fluorescence spectrosopy technique, the reaction of ferrate and benzopyrene (BaP) in aqueous phase which is a representative polycyclic aromatic hydrocarbon, was also investigated. The maximum degradation (49.5%) of BaP was gained at conditions of pH 9.5, Fe(VI): BaP molar ratio of 1:5, reaction time of 3 hours.

Abstract: The composites of expanded ghaphite with TiO₂ (EG/TiO₂) have been prepared in the method of precursor mixing, and the optimum preparation conditions have been studied. The morphology and crystal structure of the EG/TiO₂ composites have been characterized by the means of SEM and XRD. Also their performance of decolorization for methyl orange solution has been researched. The results are shown as follows: the EG/TiO₂ composites maintain the rich porous and network structure of EG, and a lot of anatase TiO₂ particles widely distribute on surfaces and in layers of EG. Compared with TiO₂ sol, taking tetrabutyl titanate as titanium source, the prepared EG/TiO₂ composites have better performance. Increasing the added amount of tetrabutyl titanate, the decolorization rate of methyl orange solution increases at first, and then decreases. When adding 2 mL tetralbutyl titanate, the decolorization rate is at the peak, up to 98.4%. These results show the composites have excellent performance of decolorization for methyl orange solution. We suppose it is mainly due to the interaction between the adsorption of EG and the degradation of TiO₂ particles.

Abstract: The most potential method of selective catalytic reduction (SCR) to remove NOx from diesel engine emissions is very effective in NOx reduction with an efficiency up to 95%. However, the current SCRs have a limitation on operation temperature and a narrow operation temperature window. In this paper, the V-W based catalysts were used in the investigation to improve the low temperature performance of NOx conversion by doping Cu and Mn into V-W based catalyst. The temperature range studied was between 150 °C and 550 °C with an interval of 50 °C. The honeycomb catalysts were prepared by an impregnation method. The study also included characterization of catalysts by BET, XRD, TPD and XPS methods.It is found that NOx conversion performance of the V-W based catalyst increases with the increase of reaction temperature. After the metal Cu or Mn doped into the catalyst, it offers an improvement in the catalytic performance. Among all the catalysts studied, the mixed metal catalyst of Cu-Mn-V-W catalyst is found the most potential one, not only because of its higher NOx conversion rate at a low temperature, but also because of its wider operation temperature window.

Abstract: TiO₂ photocatalyst modified with N and Fe (Fe-TiO_2-xN_x) was obtained. Bimetal and nitrogen co-modified TiO₂ (Ag/Fe-TiO_2-xN_x) was prepared by photo catalytic reduction of Ag on the Fe and nitrogen co-modified TiO₂. The catalytic activity of sample for photocatalytic reduction of nitrate under visible light was tested. And the bimetal and nitrogen co-modified TiO₂ was characterized by XRD, XPS, TEM and UV-vis diffuse reflectance spectrophotometry.

Abstract: A tentative plan of phenol wastewater treatment by using the carbon cycling micro-electrolysis reactor (CCMER) was designed and its result was analyzed with Design-Expert 7.1 software. The experiment results showed that the relation model between COD_cr removal efficiency and the effective factors with different operating variables was established and normal probability plot of residual, response surface and contours for desirability function of COD_cr removal efficiency with different effective factors were given. A group of optimization parameters for COD_cr removal efficiency would be consulted by Design-Expert 7.1.

Abstract: This work comparatively investigated the formation of ketoacids of a filtered river water in synthetic goethite-catalyzed ozonation and ozonation alone. Results indicate that the catalytic ozonation produces less pyruvic acids and total ketoacids than ozonation alone. In addition, the yields of total ketoacids of the filtered water after catalytic ozonation increased as ozone dose increased and contact time extended. In comparison to ozonation alone, FeOOH/O₃ further enhanced the degree of oxidation of the macromolecular intermediates or by-products such as pyruvic acid due to more •OH generation. However, Bio-filtration is still proposed to follow the catalytic ozonation to ensure the microbial stability in water distribution systems.