Yung Hsu Hsieh

Photocatalytic Degradation of Methylene Blue Using Porphyrin/TiO2 Complexes Activated by Visible Light

The use of TiO2 as photocatalyst to degrade the organic compounds is an effective method of oxidation process and has been widely studied in environmental engineering. However, TiO2 absorbed the UV light which is only small part of sunlight reaching earth surface to activate photocatalytic procedure is a major disadvantage. Therefore, studies on the development of new TiO2 that its photocatalytic activity can be activated by visible light which is the major part of sunlight will be valuable for field application. In this study, we evaluate the photocatalytic degrading efficiency of porphyrins/TiO2 complexes on the organic pollutants under irradiation with visible light (λ= 419 nm). The results showed that the photodecomposition efficiency of methylene blue were up to 95% and 90% respectively after using NiTPP/TiO2 and ZnTPP/TiO2 irradiated with visible light for 6 h. These evidences reveal that the system of porphyrin/TiO2 complexes has significantly high efficiency of photocatalytic degradation under visible light irradiation.

Optimization of Preparation of the TiO2 Photocatalytic Reactor Using the Taguchi Method

In this study, titanium dioxide thin film was prepared using the modified chemical vapor deposition. The parameters employed to control the preparation of the catalyst include the temperature of water bath, the Ti(OC3H7)4/H2O ratio, the flow rate of carrier gas, the oxidation temperature, the oxidation time, the calcination temperature, the rotating speed of furnace, and the speed of geared motor. The orthogonal arrays in the design of experimental method proposed by Taguchi were adopted to conduct the multiple-factor experiment. The conversion rate of salicylic acid in the aqueous or heterogeneous phase photocatalysis experiment was employed to identify the optimal conditions for assembly. The results indicated that a higher conversion ratio of the organic substance could be achieved under catalytic oxidation temperature of 400°C, calcination temperature of 550°C, and spraying speed of 30 rpm and the optimal experimental conditions obtained in this study were irradiation with intensity of 2.9 mW cm-2 on salicylic acid at concentration of 250 mg L-1 by both agitation and aeration processes (dissolved oxygen level = 8.2mg O2 L-1) at pH 5, which could achieve optimal hydroxyl radical yield of 5.1 ×10-17 M.

Catalytic Destruction and Removal of Toluene by Microwave/Fe3O4 System

A microwave/Fe3O4 catalytic system was proposed for treatment of volatile organic carbons (VOCs). This system comprises a household microwave oven modified as the reaction chamber, which was fitted with a vertical, cylindrical quartz reactor comprising a catalytic packed column filled with granular Fe3O4, a microwave catalyst of iron (II, III) oxide. Experimental results showed that the destruction and removal efficiency (DRE) of toluene by microwave alone was close to zero, but with the microwave/Fe3O4 system, the temperature of the catalytic packed column increased rapidly and reached thermal balance within 10-15 min. Analysis of the rear gas after combustion showed that most of the toluene was thermal oxidized into CO2 and H2O. The successful application of the proposed microwave/Fe3O4 system to thermal destruction of toluene promises a new technology for treatment of VOCs.

Azo Dye-Yellow 17 Wastewater Photocatalytic Degradation of by UV/TiO2 Combined with Ultrasonic Procedure

. The study combined UV/TiO2 with ultrasonic procedure to degrade azo dye wastewater of Acid Yellow 17. The effects of factors including pH value, initial concentration of dye, and quantities of TiO2, Fe (II), and Fe (III) added on the removal efficiency of azo dye Acid Yellow 17 were investigated. Experimental results revealed significant additive effect attributed to the combination of two procedures under 13-watt UV irradiation and 10-watt ultrasound. Analysis of the catalyst properties indicated no evident changes in the appearance of crystal and TiO2 catalyst by UV/TiO2 combined with ultrasonic procedure. However, the specific surface area was increased by approximately 53%. No effective formation of hydrogen peroxide (ND  1 mg/L) proved that the addition of Fe (II) and Fe (III) failed to induce the Fenton-like reaction effectively. Nevertheless, the addition of Fe ions affected significantly the initial adsorption and the degradation rate of the dye. Moreover, the treatment efficiency of Fe (III) was found to be superior to that of Fe (II) under the same concentration.

Degradation of Azo Dye Wastewater by UV/TiO2 Combined with an Ultrasonic Procedure

The study combines the UV/TiO2 and an ultrasonic procedure to degrade the azo dye wastewater of Acid Yellow 17 and investigates the effects of various factors including the quantities of TiO2 and iron ions added on the efficiency of the removal of the azo dye wastewater of Acid Yellow 17. The experimental results reveal the a significant additive effects occurs through the combination of the two procedures under the 13 watts UV irradiations and 10 watts ultrasound. The analysis of the catalyst properties indicates that there are no evident changes of the appearance of the crystal and TiO2 catalyst when UV/TiO2 is combined with ultrasonic procedures. Since the formation of hydrogen peroxide (ND≦1 mg L-1) was not detected during the reactions, the additions of Fe (II) and Fe (III) are unable to induce the Fenton-like reaction effectively. Nevertheless, the additions of Fe ions significantly affect the degradation rate of the dye. Moreover, the effect of Fe (III) was found to be superior to that of Fe (II) under the same concentration.

Catalytic Destruction and Removal of Dichloromethane in the Microwave/Fe4O3 System

In this study, a new catalytic oxidation technology, microwave/Fe3O4 system, was used to treat volatile organic carbons (VOCs) and dichloromethane (DCM) was selected to simulate industrial emissions of VOCs. This system comprises a household microwave oven modified as the reaction chamber, which was fitted with a vertical, cylindrical quartz reactor comprising a catalytic packed column filled with granular Fe3O4, a microwave catalyst of iron (II, III) oxide. Experimental results showed that the destruction and removal efficiency (DRE) of DCM by microwave alone was close to zero, but with the microwave/Fe3O4 system, the temperature of the catalytic packed column increased rapidly and reached thermal balance within 10-15 min. Analysis of the rear gas after combustion showed that most of DCM was thermal oxidized into CO2 and H2O. The successful application of the proposed microwave/Fe3O4 system to thermal destruction of DCM promises a new technology for treatment of VOCs.

Preparation and Photocatalytic Activity of Sol-Gel Method Derived La Doped TiO2/ITO Photocatalytic Electrodes

La–doped TiO2 thin films were synthesized using TTIP, IPA , Acetic acid ,and La2¬O3 as precursors by sol-gel method and dip-coating method. The different molar raitos of La/Ti ( 0.025,0.050,0.075 and 0.100 ) were supported on ITO glass to product photocatalytic electrodes. The properties of both TiO2/ITO and La- TiO2/ITO photocatalytic electrodes were characterized by FE-SEM,BET and XRD. The FE-SEM and BET analytical results demonstrate that La-TiO2/ITO particles have uniform shape and small size (＜10nm ) compared with TiO2/ITO. Anotherway, the XRD resultes show that when more molar raitos of La/Ti the crystallites become more percent to of rutile. The La-TiO2/ITO photocatalytic electrode with molar raito 0.05 shows the best photocatalysis with mineralization rate after four hours reaction. On this condition, different Acid Yellow 17 initial concentration and UV light intensity have been research. Applied potential 2.0V would effectively increase the decolonization rate under visible light irradiation.

The Study on the Decomposition of Azo Dye by La-Modified TiO2

The La/TiO2 photocatalyst was prepared by lanthanum into TiO2 structure in a sol-gel process. The catalyst was characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), ESCA, and Brunauer Emmett Teller (BET) analyses. Photocatalytic activities of the supported catalysts were examined through decomposition process of azo-dye Acid Yellow 17 solution under UV irradiation. The results showed that the particle size of TiO2 is about 20 nm, and the particle of La/TiO2 is about 10 nm. The crystal structure is mainly in anatase phase, the contents of the rutile phase increase with the increase of the amount of doped lanthanum. The adsorption capacity of La/TiO2 catalysts increases with lanthanum dosage in the acidic solution. The contribution of actual photodecomposition was determined by desorption process, after the photocatalytic reaction. In the acidic solution, better photodecomposition efficiency is achieved than in the neutral or alkaline solution. The experiments demonstrated that the optimum doping of La at 10 mol %, the maximum photodecomposition in dye concertration at 15 mg L-1 and photocatalytic dosage at 0.75 g L-1, achieving the highest effect.

Characterization and Photocatalytic Activity of Composite La-TiO2/ITO Thin-Film Electrodes

The different molar ratios of La/Ti (0.025, 0.050, 0.075 and 0.100) photocatalytic electrodes use in this study were synthesized by sol-gel method and dip-coating method. The XRD pattern of TiO2/ITO presents only anatase phases, [1] but for La-TiO2/ITO presents both anatase and rutile phases. The SEM image of the La-TiO2/ITO showed particles of regular shapes with smaller size (＜10nm) compared to the TiO2/ITO, which presented uniform particles of spherical structure and larger size （20nm）.The La-TiO2/ITO photocatalytic electrode with molar ratio 0.050 shows the best ability both on the absorbtion and photocatalytsis. Applied potential 2.0V would effectively increase the photoelectrocatlaytic activity under visible light irradiation.

Visible Light Activated Photocatalytic Degradation Effect of V-TiO2 on Azo Dye Wastewater

In this study, the V-doped TiO2 was synthesized by sol-gel method and we evaluate the photocatalytic degrading efficiency of V-TiO2 complexes on azo dye wastewater under irradiation with visible light (λ= 419 nm). The results showed that the Anatase structure and nano size of V-TiO2 complexs were formed and they had better photo-response to visible light than pure TiO2. The efficiency of decoloriztion or destruction efficiency was less than 6 % using TiO2 alone but efficiency of 0.10VT-I was up to 90% after irradiated with visible light for 240 min. These evidences also reveal that the system of V-TiO2 complexes can directly utilize the sunlight and can be used to treat organic pollutants in the practical wastewate treatment factories.