Materials Science Forum Vols. 544-545

Abstract: 1) Upon comparing Ceramic products, which have been made into samples by the exactly same construction method as prefabbed wall of apartment, with the existing products, it is revealed that there would beno diminution effect on Pollutants like TVOC and HCHO. On the contrary, from the Ceramic applied prefab-wall, some pollutants, which were not seen from normal wall-panel, had been emitted additionally. 2) When we spreaded seven kinds of catalyst products on the surface of samples of MDF furniture and tested, two of those applied samples showed stronger tendency regarding the TVOC and HCHO emission than unapplied samples. Consequently, it is clarified that there's no effect of eliminating the pollutants like TVOC and HCHO from the application of catalysts as well as ceramic. In this regard, when we consider all the results collectively which were earned from these analysises up to now, using indiscreet after-treatment materials in residential place should be applied only after prudent examination.

Abstract: A photocatalytic system for wastewater treatment from textile industries was constructed and tested for its efficiency. The system consisted of two units – a photoreactor for dye decomposition and a catalyst recovery unit. The photoreactor was an annular plug flow photoreactor under irradiation of 36 W Toshiba blacklight. The catalyst recovery unit was 42 L of sediment tank for TiO2 catalyst recovery. In our study, a Cibra Cron red R-W 150% (an anionic azo dye) was used to prepare a synthetic textile wastewater. The experimental parameters such as flow rate, pH, dye initial concentration, catalyst loading and setteled time that affected the system performance were investigated. The photodegradation kinetics were found to follow the Langmuire - Hinshelwood model and also depended on the TiO2 concentration and the pH. The optimum condition for photocatalytic decomposition was at pH 3 and at 1 g/L of TiO2 catalyst loading. The reaction rate constant, k and the adsorption constant, K for the scale-up photoreactor were 3.345 mg/L-min and 0.0204 L/mg, respectively. For the catalyst recycle unit, the overflow and underflow concentration of the TiO2 catalyst were 2.00 and 0.002 mg/L, respectively, at 100 ml/min of inlet flow rate, 50 ml/min of overflow and 50 ml/min of underflow.

Abstract: Adhesion between TiO2 coatings and the fabrics was improved by using a silane adhesive agent. To investigate a suitable method of applying adhesive agent, two different coating methods were conducted. The silane was either mixed with Ti precursor for fabric dipping, or coated onto the fabrics before dipping them in a Ti precursor. The effect of Ti precursor, sol and colloid, on coating morphology was also studied. It was found that continuous coating with no cracking was obtained when the fabrics were pre-treated with the silane. The TiO2 coatings had good adhesion, regardless of the method of applying the adhesive agent. Thick, cracked coatings were obtained from Ti colloid precursor while continuous coating was obtained from the Ti sol precursor.

Abstract: Ag-doped TiO2 catalyst employed as the oxidation catalyst candidate was prepared by two methods, co-precipitation and dip coating method. Co-precipitation method was conducted by adding AgNO3 into the titanium precursor before gelation and then the obtained solution was coated on the alumna beads. Dip coating method was conducted by coating the first layer on alumina beads with titanium precursor followed by coating the second layer with AgNO3. The fired Ag-doped TiO2 coated on alumina beads was used as catalyst for catalytic oxidation of methanol and carbon monoxide by using oxygen as oxidizing agent in a gas-phase reactor. The methods of catalyst preparation were found to affect the catalytic efficiency. Dip coating method showed better oxidation reaction as Ag-doped TiO2 catalysts were well dispersed on the alumina beads.

Abstract: TiO2 photocatalysis has attracted a great deal of attention during the last three decades. One major goal in this field is the design and preparation of TiO2 based photocatalysts possessing high photocatalytic activity to satisfy the requirements for practical applications. For the development of successful strategies to achieve this goal it is of utmost importance to improve the mechanistic understanding of the basic principles of photocatalysis. Therefore, various nanosized TiO2 photocatalysts including pure TiO2, Fe(III)-doped TiO2 and platinized TiO2 have been synthesized in our laboratories and their photocatalytic activity has been studied in detail. In particular, the correlation between the structural characteristics of these newly synthesized catalysts and their photocatalytic activity has been addressed. To explain the unexpected behavior of these materials novel mechanistic principles, i.e., the antenna mechanism and the so-called deaggregation concept have been developed and will be explained in this review.

Abstract: The effect of various reaction factors such as amount of Ni loaded, temperature, and variety of supports on the methane conversion were investigated to obtain higher methane conversion. The high activities were observed over Ni(10 wt%)/SiO2 catalyst and at 650oC of reaction temperature. Catalysts using mesoporous supports such as SiO2 and MCM-41 showed good catalytic activity and stability.

Abstract: TiO2 films were deposited by using mid-frequency twin magnetron reactive sputtering technique at ambient temperature on quartz and Si wafer. The films were annealed after deposition. The phase composition and surface morphology of the TiO2 films were characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy, while the optical properties and contact angle were measured using a UV-Vis spectrophotometer and a contact angle meter. It is indicated that anatase phase dominates below 900°C and a mixture of rutile and anatase exists in the film annealed at 1000°C. Furthermore, the hydrophilic property depends on phase composition and morphological change in TiO2 films.

Abstract: Even though activated carbon fibers (ACF) have been attractive due to high specific surface area and uniform micropore structure, there are only a few reports about the photocatalyst immobilization on ACF or their photodegradation behavior for removal of organic pollutants. In this study, ACF were selected as adsorptive support for photocatalyst immobilization. As photocatalysts, TiO2 nanoparticles were synthesized by using a N2-diluted and oxygen-enriched co-flow hydrogen diffusion flame. The visible flame length of 150mm was obtained by direct photographs. Flame temperature was measured by rapid insertion measurement technique with a R-type (Pt/Pt-13%Rd) thermocouple which was in wire shape (127μm diameter). TiO2 particles were sampled by using a high temperature particle sampler and then were coated on ACF filters. The sampling was carried out at 70mm and 110mm above the burner. The structure of TiO2 particles was analyzed by XRD. TiO2 coated ACF filters were characterized by FESEM-EDX and BET analyses. TiO2 particles on ACF filters were found to be agglomerated particles and the size of primary particles was approximately 50nm. The structure of TiO2 particle was anatase-phase crystalline structure. The specific surface area of TiO2 coated ACF filter was enhanced to be 1700~1860m2/g, depending on the sampling location, and the pores were micropores, regardless of the sampling location.