High Decomposition Efficiency Research Articles

ZnO-mediated photocatalytic degradation of Benzopurpurine BP4B in aqueous solution

The photocatalytic degradation of a commercial azo dye Benzopurpurine 4B (BP4B) in aqueous solution was investigated under UV-A light at different operating conditions, including irradiation time, pH solution, initial dye concentration, amount of catalyst, light intensity as well as band gap of other semiconductor groups by UV-spectrophotometric monitoring. The highest decomposition efficiency was obtained at pH 8 as a result of 97.24 % degradation of BP4B for 80 min of irradiation time. Photodecomposition reaction of BP4B dye was correlated with pseudo-first-order kinetic model. The degradation data of BP4B dye were satisfactory described by Langmuir-Hinshelwood (L-H) mechanism.

Study on Photocatalysis Degradation of Phenol by Using Tourmaline/ TiO<sub>2</sub> System as Catalyst

The authors use the method of titanium salts on the surface of tourmaline particles hydrolyzing and coating TiO2 to construct Tourmaline/ TiO2 system in different conditions and characterize the catalyst system by TEM and SEM and Raman Spectra Pattern. The writers used phenol solution as the target compound to observe the removing effects of catalysis system on phenol under dynamic conditions. The results showed that: a. the compound photo catalysis system had brilliant decomposition performance on phenol. b. It would reach high decomposition efficiency on the initial phase of reaction when the rate of tourmaline to TiO2 was 1:1 and the decomposition efficiency could be 96.29% at 120min when the rate was 0.2, which was 26% higher than that of pure phase TiO2.

A Study of Sulfonol Decomposition in Water Solutions Under the Action of Dielectric Barrier Discharge in the Presence of Different Heterogeneous Catalysts

The decomposition kinetics of sulfonol (surfactant) in water solutions as well as the formation kinetics of decomposition products under the action of an oxygen dielectric barrier discharge (DBD) at atmospheric pressure in the presence or absence of TiO2, NiO and Ag2O catalysts in the plasma zone was studied. The DBD discharge was shown to have high decomposition efficiency (phenol-up to 98%, sulfonol-up to 80%). In a plasma-catalytic hybrid process, the efficiency of organic substances decomposition was higher than efficiency for the DBD treatment without catalyst. The catalysts application resulted in a change in the ratio and yield of decomposition products.

Application of Dielectric Barrier Discharge for Waste Water Purification

This study considers treatment of real city rain sewage under the action of an oxygen dielectric barrier discharge (DBD) at atmospheric pressure in the presence or absence of TiO2 catalyst in the plasma zone. The DBD discharge has been shown to have high decomposition efficiency (up to 98%) for oil hydrocarbons, phenols and synthetic surfactants. The discharge action resulted in the decrease of heavy metal (Pb, Cd, Fe, Mn) content as well. In a plasma-catalytic hybrid process, the efficiency of organic substances decomposition was higher than efficiency for the DBD treatment without catalyst.

Performance Characterization of Pellet Catalytic Beds for Hydrogen Peroxide Monopropellant Rockets

The present paper illustrates a comprehensive experimental campaign carried out in order to assess the capability of four especially developed catalytic beds to decompose hydrogen peroxide under operational conditions representative of typical application to small monopropellant rocket engines and to characterize the resulting performance of the thruster. The catalytic beds have been integrated in a reconfigurable thruster prototype and tested in a suitable test facility. All beds have shown high decomposition and propulsive efficiencies, well in excess of 90%. In particular, two catalytic beds (indicated as LR-III-106 and CZ-11-600) have been, respectively, able to decompose up to 13 and 11 kg of 90%hydrogen peroxide (equivalent to 433 and 366 g of decomposedH2O2 per gram of catalyst) in 2500 and 2000 s of continuous thruster operation. They exhibited C-star efficiencies higher than 95%. The experimental results have also indicated two main sources of catalyst degradation. In low-porosity catalysts the decay of chemical activity affects the temperature efficiency and causes theflooding of thefirst portion of the catalytic bed,whereas highly porous catalysts experience thermal rupture of the carrier,which leads to excessive growth of the pressure drop across the catalytic bed.

The Removal of Nitrate by Nanoscale Iron Particles Produced Using the Sodium Borohydride Method

This study was conducted to investigate removal of nitrate by nanoscale zero-valent iron (ZVI) particles in aqueous solution. ZVI particles was produced from wasted acid that is by-products of a pickling line at a steel work. The reaction activity of ZVI particles was evaluated through decomposition experiments of NO3-N aqueous solution. Addition of a larger amount of ZVI particles resulted in a higher decomposition rate. ZVI particles showed higher decomposition efficiencies than commercially purchased ZVI particles at all pH values. Both ZVIs showed a higher decomposition rate at a lower pH. Virtually no decomposition reaction was observed at pH of 4 or higher for purchased ZVI. The ZVI particles produced directly from wasted acid by the sodium borohydride method were not easy to handle because they were very small (10-200 nm) and were oxidized easily in the air.

Decomposition of gas‐phase aromatic hydrocarbons by applying an annular‐type reactor coated with sulfur‐doped photocatalyst under visible‐light irradiation

AbstractBACKGROUND: Unlike many water pollution applications, visible‐light‐driven photocatalysis of gas‐phase pollutants has been reported only rarely. The present study was performed to investigate the feasibility of applying S‐doped visible‐light‐induced TiO2 to treat gas‐phase aromatic hydrocarbons, using a continuous air‐flow annular‐type reactor.RESULTS: The prepared S‐enhanced TiO2 powders, along with a commercially available TiO2 powder (Degussa P‐25), were characterized using diffuse reflectance UV‐VIS‐NIR spectrophotometry, Fourier transform infrared (FTIR) spectrophotometry, X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetry (TG) analyses. A photocatalytic activity test exhibited an increasing trend in degradation reaction rates with increase in flow rate but a decreasing trend in terms of degradation efficiencies. Several experimental conditions induced reasonably high decomposition efficiencies with respect to toluene, ethyl benzene and o,m,p‐xylenes (close to or above 90%), although benzene exhibited a somewhat lower decomposition efficiency.CONCLUSIONS: The S‐doped TiO2 and undoped P25 TiO2 powders exhibited different catalyst characteristics. The results demonstrate that an annular‐type reactor coated with visible‐light‐activated S‐doped TiO2 can serve as an effective tool to treat gas‐phase aromatic hydrocarbon streams. Copyright © 2009 Society of Chemical Industry

Numerical modeling of hydrogen production from ammonia decomposition for fuel cell applications

The hydrogen production from NH 3 decomposition for fuel cell applications using packed Ni–Pt/Al 2O 3 particles as the catalyst is theoretically and numerically predicted. The results show that by adopting the chemical reaction model for a packed-bed reactor used in the methanol-steam reforming with ZnO/Al 2O 3 as the catalyst, the numerical model predicted satisfactory results on the NH 3 decomposition efficiency as compared with the experimental data. For various catalyst bed porosities and particle sizes, the numerical results indicated that porosity and permeability of the catalyst bed produce an insignificant effect on the NH 3 decomposition. Based on this finding, a one-dimensional plug flow model is developed and the predicted species molar fraction variations and NH 3 decomposition efficiency are found in good agreement with the numerical simulations. From the numerical and theoretical results, it is found that the NH 3 volumetric flow rate fed into the reactor is an important factor that determines the reaction temperature and decomposition efficiency in addition to the catalyst. Because of a longer NH 3 residence time inside the reactor, lower reaction temperature can be employed for a high decomposition efficiency when the NH 3 flow rate is low.

Combustion Abatement Technology for Perfluoro Compounds Reduction

Various efforts such as the optimization of the production process and the adoption of alternative gas has been made to reduce the emission of PFCs used in the process of semiconductor manufacture. However, in order to achieve the reduction of PFCs whose consumption is increasing, the exhaust-gas treatment equipment with the high performance of decomposition is needed. The demands for the equipment from the viewpoint of design for the thermal decomposition are discussed below. The reductive atmosphere is needed for the thermal decomposition of PFCs to prevent the recombination of dissociated fluorine. The distributed flame which can effectively apply the point of high temperature of the flame is used to improve the efficiency of heating. To create the reductive atmosphere, at first, the combustion using excessive concentration of the main burner fuel takes place and next, the auxiliary fuel and the combustion enhancing gas are provided. In the case of decomposition of CF4, which is one of the most difficult substance to be degraded, high decomposition efficiency was achieved by using O2 for the combustion enhancing gas. By analyzing the data of the internal temperature distribution of the equipment and the decomposition efficiency of the gases, the decomposition temperature of the typical PFCs to achieve decomposition ability more than 95% are shown below. CF4 -1600°C, C2F6 -900°C, SF6 -1000°C, NF3 -800°C

Investigation into NanoTiO2/ACSPCR for Decomposition of Aqueous Hydroquinone

The suspended TiO2 powder enjoys free contact with pollutant molecule in a photocatalytic reactor; it can generally achieve better efficiency than the immobilized TiO2 catalysts. However, the separation and reuse of this catalyst powder from treated water often limit its application in practice. An adsorptive activated carbon-supported titanium dioxide photocatalyst TiO2/AC was prepared using nanosized titanium dioxide (anatase) immobilized on activated carbon powder by a novel preparation technique with polyacrylic ester emulsion. Meanwhile, the heterogeneous photocatalytic decomposition of aqueous hydroquinone over the ultraviolet irradiated TiO2/AC photocatalyst was carried out with high decomposition efficiencies in a slurry photocatalytic reactor (SPCR), which provided the effective contact of TiO2/AC photocatalyst and reactant. The pH value, the ratio of TiO2/hydroquinone, the aerating, and the concentration of H2O2 on photocatalytic decomposition of hydroquinone were discussed in detail. Experimental results showed that not only did the photocatalyst have a high adsorption performance and a good photocatalytic activity for hydroquinone but also the catalyst was easily separated from SPCR and recycled as well. Moreover, it was found that the reaction kinetic fixed the pseudo-first-order kinetic equation, which provided a detailed kinetic understanding of photocatalytic degradation of hydroquinone in SPCR.

Photocatalytic activity and characterization of sol-gel-derived Cr(III)-doped TiO2-coated active carbon composites

Cr(III)-doped, TiO2-coated active carbon (Cr–TiO2/AC) were prepared by a sol–gel method. The effect of supports, including TiO2 and active carbon (AC), on the molecular structure and photocatalytic activity of chromium oxide for complete decomposition of EDTA has been examined with respect to the content of Cr on the catalyst surface. The photocatalytic activity of the Cr–TiO2/AC composites was evaluated in the decomposition of EDTA solution under UV irradiation. The results indicate that Cr–TiO2/AC has a higher efficiency in decomposition of EDTA than TiO2, TiO2/AC or active carbon. This was attributed to the different functions of active carbon and chromate species. (1) Nanosize TiO2 particles on composites were not reunited, possible because active carbon retards transformation of anatase into rutile and decreases the crystallite size. (2) Production of high concentrations of organic compound near Cr–TiO2. (3) Carbon in active carbon causes some of the TiO2 to reduce to Ti3+ ions, which prevents electron–hole pair recombination. (4) Formation of polychromate species, with a stronger redox capability, on the surface of TiO2/AC. It was found that the addition of Cr to TiO2 sol could suppress the grain growth of TiO2 crystals and increase the hydroxyl content on the surface of TiO2/AC. The photocatalytic efficiency and activity of the composites remained good, even after three cycles.

Processing and properties of transparent sulfated TiO 2 thin films using sol–gel method

For this study, transparent sulfated TiO 2 thin films were prepared from Ti alkoxide. Vacuum ultraviolet illumination in air at 180 °C was demonstrated to be an effective pretreatment for reproducible preparation of crack-free sulfated TiO 2 thin films. The film provides a high photoinduced wettability conversion rate and photocatalytic decomposition efficiency on gaseous n-hexane under proper conditions. This result is attributable to the accelerated decomposition of intermediates by a strong inorganic acid on the surface or to the resultant high quantum yield by suppressing the recombination between electrons and holes on the film surface.

超臨界水処理による再生アスファルト舗装用骨材のセメントコンクリートへの適用

Supercritical water, a solvent with a very high decomposition efficiency, is especially applicable to waste treatment, requiring no organic solvents or incinerators. This paper discusses the technology to remove asphalt from the asphalt mixture by using Supercritical water as well as the promising applications of the recycled aggregates for the manufacture of cement concrete. In this experiment, the strength and durability (drying shrinkage, carbonation and freezing and thawing) tests of concretes using recycled aggregates produced by supercritical water treatments were conducted to evaluate the applicability of the aggregates to cement concretes. The results reveal that the strength and carbonation behavior were similar to using virgin aggregate, however, the drying shrinkage and the scaling of the concrete with high water cement ratio tended to increase as compared to the use of the virgin aggregate.

Epitaxial Growth of SiC on Silicon on Insulator Substrates with Ultrathin Top Si Layer by Hot-Mesh Chemical Vapor Deposition

The epitaxial growth of SiC on silicon-on-insulator (SOI) substrates with an ultrathin (<10 nm) top Si layer by hot-mesh chemical vapor deposition (CVD) was investigated. This method utilizes heated tungsten wires arranged in a mesh, which promotes the high decomposition efficiency of H2 gas. Using the hot-mesh CVD method, SiC epitaxial films were successfully grown on SOI substrates without voids being formed, which are formed readily in thin (<100 nm) top Si layers at temperatures above 800 °C. Some micropatterns for micro-electro-mechanical systems were fabricated on SiC on insulator (SiCOI) structure substrates by reactive ion etching and wet etching.

Photocatalytic degradation of methylene blue in a sparged tube reactor with TiO2 fibers prepared by a properly two-step method

Abstract The photocatalytic oxidation of methylene blue has been performed in the presence of suspended TiO2 fibers prepared by a properly two-step method in an air-sparged tube reactor. The key factors affecting the methylene blue oxidation efficiency were investigated, including the initial concentration of methylene blue, the pH value and the electric power of UV lamp. For photodegradation of methylene blue, it was observed that TiO2 fibers have a higher decomposition efficiency than the self-made TiO2 powders, as well as the commercial P25. The optimal conditions were a concentration of 9 × 10−3 mol/l at pH 6 with 40 W of illumination for the fastest rate of methylene blue photodegradation. Diffuse reflectance UV–Vis analysis showed a shift in the threshold absorption value and a corresponding increase in bandgap energy for TiO2 fibers, which is considered to be responsible for the decrease in TiO2 fibers photoactivity after 15 trials.

A method for decomposition of hexachlorobenzene by γ-alumina

A method of decomposing hexachlorobenzene (HCB) by γ-alumina was investigated at low temperature of 300 °C. It was found that HCB was rather quickly decomposed under such a condition. Decomposition efficiency (DE) increases with increasing the surface area of γ-alumina. Pretreated γ-alumina has a better performance for the decomposition reaction. A high decomposition efficiency within the short reactive time of 60 min was achieved to be 94.2%, which was obtained by preheating γ-alumina with the surface area of 220 m 2 g −1 at 450 °C for 2 h. High surface area and appropriate pretreatment temperature probably provide more reactive sites such as the isolated OH groups and Al 3+ sites surrounded by O 2− sites. These sites may induce the decomposition of HCB via a main ring-cracking process. The present study, hopefully, holds the promise for the eliminating of HCB contained hazardous materials in industrial application.

Decomposition of 2,4',5-Trichlorobiphenyl by Using Molten Salt

The decomposition of 2,4',5-trichlorobiphenyl as a derivative of PCB was studied by means of the injecting the solution into NaOH-Na2CO3 or KOH-K2CO3 molten salts. The solution of 2,4',5-trichlorobiphenyl dissolved in an organic solvent were fed into the molten salts together with the carrier gas (N2-21%O2) through the injection tube. The experiments were carried out in the temperature range of 500-700{degree sign}C by immersing the injection tube into the molten salts. Potassium system showed relatively higher decomposition efficiency than sodium system at low temperature. The decomposition efficiency of 2,4',5-trichlorobiphenyl depended on the temperature and was approximately 99.999% over 600{degree sign}C in both systems.

Nano-TiO 2 particles with increased photocatalytic activity prepared by the miniemulsion method

The water-in-oil (W/O) miniemulsion system was used to prepare nano-TiO 2 particles. The nano-TiO 2 particles were characterized by XRD, FTIR, DRS, SEM and BET surface area analysis. The photoactivity of nano-TiO 2 particles was evaluated by photocatalytic degradation of methyl orange. The results show that nano-TiO 2 particles, prepared by miniemulsion, have a higher efficiency in decomposition of methyl orange than P25 and TiO 2 synthesized via the sol–gel method due to the high surface area and optimum phase constitution.

Effect of TiO 2 powder addition on sonochemical destruction of 1,4-dioxane in aqueous systems

Effects of TiO 2 powder addition on sonochemical destruction of 1,4-dioxane in water were investigated through comparison of a SiO 2 powder that had similar specific surface area. Results show that addition of TiO 2 is more effective for decomposition of 1,4-dioxane in water than addition of SiO 2. The contribution of photocatalytic destruction through sonoluminescence is not a dominant mechanism for acceleration of sonochemical reactions by adding TiO 2. Sonication of TiO 2-added water generated thermally excited holes in this case. Moreover, intrinsic oxygen vacancies in TiO 2 surface play an important role in achieving high decomposition efficiency by producing cavitation. The addition of reduced TiO 2 powder increases both the ultrasonication energy that is consumed in water and the destruction efficiency of 1,4-dioxane.

이원 촉매를 이용한 과산화수소 가스발생기

고농도 과산화수소는 별도의 산화제가 필요치 않은 단일추진제로써 상온에서 액상인 장점이 있어 다양한 장치의 추진제로 이용되고 있다. 본 연구에서는 상온에서의 시동 성능 보완을 위해 이원 촉매층을 이용한 실험적인 연구를 수행하였다. 상온에서의 뛰어난 성능을 바탕으로 <TEX>$K_2MnO_4$</TEX>를 도입부의 촉매로 선정하였으며 이를 위해 알루미나 졸-겔법을 이용한 새로운 코팅법을 개발하였다. 가스발생기를 이용한 반응실험을 통해 설계유량에 적합한 기화기의 길이를 결정하였고 이를 이용한 이원 촉매 가스발생기의 성능평가를 수행하였다. 성능평가 결과, <TEX>$10^{\circ}C$</TEX> 이하의 온도에서 냉시동(cold-start)에 성공하였으며 높은 분해효율을 확인하였다. The rocket grade hydrogen peroxide has been widely used as a monopropellant in propulsion systems. In the present paper, we described an experimental study of a catalytic reactor that employs two stage catalyst beds to enhance the low temperature performance of the reactor inlet. <TEX>$K_2MnO_4$</TEX> was chosen as the catalyst for the initial stage of the reactor bed for its superior behavior in the low temperature regime. Alumina sol-gel method was successfully applied for coating <TEX>$K_2MnO_4$</TEX> on a reactor bed of cordierite monolith. LSC was used for the catalyst of the second stage of the reactor. The reactor with combined catalyst beds was built and tested to exhibit superior performance in low temperature regime and high decomposition efficiency.