Charusporn Mongkolkachit

Fabrication and Photocatalytic Degradation of TiO2/Porous Activated Carbon-Zeolite Composite Cylinder

Activated carbon, zeolite and titanium dioxide are wildly used for removing the organic compounds in waste water. Although, these materials exhibit high performance (in powder form), reclaiming of these materials from the waste water treatment system is still hard. The objective of this study is to fabricate hollow cylinder activated carbon-zeolite samples which were used as a porous substrate. Various ratios of activated carbon, zeolite NaA and clay were mixed with special binder to form dough before extruded to be hollow cylinder shape. The hollow cylinder samples were cut into 2.5 cm long and then were fired at 600 °C for 2 hours under 5%CO2+N2 atmosphere. The fired samples were dip-coated with TiO2-P25 and fired at 600 °C for 1 hour under 5%CO2+N2 atmosphere for testing the photocatalytic degradation of lignin solutions under UV light. The results showed that the strength of fired samples increasing with the ratio of clay increased. The XRD patterns of samples having clay addition showed peaks of zeolite and quartz. The physical properties, microstructure and photodegradation will be discussed.

Honeycomb Structures of TiO2-modified Hydroxyapatite Composite forMicrobial Filtration Application

Honeycomb structures of TiO2-modified hydroxyapatite composite (HA/TiO2) were fabricated using extrusion technique. The mixture formulations of HA/TiO2 extrusion pastes (S1-S4) were investigated to optimize the process. The filtering effectiveness of the HA/TiO2 honeycombs was evaluated by photocatalytic activity measurement and a bactericidal test. The effects of sintering temperature and honeycomb thickness on photocatalytic and antibacterial activities were additionally studied. The S3 and S4 honeycomb samples, sintered at 650°C, exhibited a similar trend in reducing methylene blue concentration. At 800°C, the S3 honeycomb sample showed a slightly faster reduction in methylene blue concentration compared to the S4 honeycomb. Honeycomb samples of 2 and 5 cm in thickness showed significantly greater photocatalytic activity than that of 1 cm such that methylene blue concentrations rapidly decreased after UV exposure for 24 hours. The S3 and S4 honeycomb samples also exhibited decomposition of both gram-negative E. coli and gram-positive S. aureus. Approximately 50% of gram-positive S. aureus and gramnegative E. coli were decomposed by the honeycombs in the sample-thickness dependent manner after 2 hours of UV exposure. Low survival ratios of bacteria (5% - 10%) were observed after 6 hours of UV exposure and the 2 mm and 5 mm thick honeycomb samples showed the greatest and most similar antibacterial activities.

Preparation of Porous Cylindrical Tubes Substrates from Zeolite and Clay for TiO2 Photocatalyst Coating

Titanium dioxide (TiO2) is the one of photocatalyst materials that widely used for decolorization of organic compounds in wastewater by photocatalytic mechanism which can be activated by UV light. Unfortunately, in the case of fine TiO2 power, filtration of the powder after water treatment process is difficult. In this research, coating or immobilizing the TiO2 powder on substrates using for removing the color of lignin concentration is interesting. The objectives of this research are to prepare the floating porous cylindrical tube substrates composed of zeolite NaA and ball clay, and then to determine the efficiency of lignin degradation. Zeolite NaA powder, Suratthani ball clay and organic binder solution were mixed before extruding and cutting to be 1.5 cm diameter cylindrical tube with 2.5 cm in length and 0.3 cm in thickness. After that, the dried tubes were fired at 650 - 800 °C for 2 hours and were then coated with TiO2-P25 suspension before re-firing at 600 °C for 1 hour in an electrical furnace. The fired uncoated tubes were characterized in terms of phase composition, porosity and radial crush strength. From the XRD pattern of the tubes fired at 800 °C showed that the zeolite NaA phase was disappeared. On the other hand, the zeolite NaA phase was found in the samples fired at another lower temperature. For the coated tubes, polyurethane foam was filled into the hole to make the tubes can be floated on the water surface. After that, the photocatalyst degradation property by determining the decreasing of concentration of lignin solution under tungsten lamp irradiation of the floated tubes were tested.

Influence of Lignite Bottom Ash on Pyroplastic Deformation of Stoneware Ceramic Tiles

Electricity generation at Mae Moh Power Plant in Lampang, Thailand, uses lignite as fuel. The output is 3.0 to 3.5 million tons of fly ash per year and 1.5 to 2.0 million tons of bottom ash per year. Fly ash is widely used in concrete application but for bottom ash, it is not very useful. When considering the phase of bottom ash containing quartz, anorthite and hematite, it was found that there are suitable chemical compositions for replacement of raw materials in ceramic tile. Generally, the stoneware tiles are composed of quartz, mullite, feldspar, and glass phase. Water absorption of stoneware ceramic tiles is below 5%, high strength, fire resistance, and low warpage. Firing or sintering at rather high temperature as 1000-1250 °C is the manufacturing process for this type of tile. The changes in crystal structure and glassy phase formation in tile texture during sintering will be often result the tile to warpage or bent. The more or less lean depends on the viscosity of the glassy phase that occurs at high temperatures in the tile if less viscosity will cause higher warping rate that effect on the shape, and quality of the workpiece. The research has reported that anorthite phase improves the viscosity of a liquid phase or glassy phase when the tile is sintering at high temperatures and lead to high density and low water absorption. This research is interested in studying the effect of using lignite bottom ash as an ingredient in ceramic tile texture to produce low water absorption type by analyzing the effect of percentage of lignite bottom ash to warpage and important properties of ceramic tiles.

Synthesis and Photocatalytic Activity of Visible-Light Responsive BiOBr/GO Composites

High efficiency BiOBr/GO composites photocatalyst were successfully synthesized via a facile precipitation method. The precursors were prepared by dissolving Bi (NO3)3.5H2O and KBr in glycerol and distilled water, respectively. Various amounts (0.1-2 wt%) of graphene oxide were added into the mixed solution precursors, and stirred at room temperature to get precipitated powder without further heat treatment. The obtained products were characterized for phase, morphology, optical properties and surface area by X-ray diffraction (XRD), transmission electron microscopy (TEM), filed-emission scanning electron microscopy (FE-SEM), UV-Vis diffuse reflection spectroscopy (DRS) and Brunauer–Emmett–Teller (BET), respectively. The morphology and structure of as-synthesized samples were composed of numerous fine plates of BiOBr dispersed on the GO sheets. The photocatalytic activities of BiOBr/GO composites were evaluated by rhodamine B degradation under visible light irradiation. As the results, the significant increase in photodegradation of BiOBr/GO composite comparing with pure BiOBr was observed. Among all samples, the composite with 1 wt% of graphene oxide showed the highest photocatalytic performance.

Effect of Sintering Additive and Pyrolysis Temperatures on Porous Silicon Carbide

Rice husk was used as a raw material to fabricate silicon carbide (SiC) ceramics. Carbothermal reduction was used together with in-situ reaction bonding as the preparation method. Rice husk was carbonized at the temperature around 700 °C in an incineration furnace. Carbonized rice husk was ground and treated with hydrochloric acid solution. After grinding, the sample powders were mixed with silicon metal powder and sintering additives (alumina (Al2O3) and magnesia (MgO)). The mixed powders were pressed and then pyrolyzed at various temperatures and pyrolysis patterns in argon atmosphere. Silicon carbide, as the main crystalline phase, was obtained in all pyrolized samples. Cristobalite was found together with silicon carbide in the samples which pyrolized only lower than 1500 °C. Amount of silicon carbide particle was increased at higher pyrolysis temperature while silicon carbide whisker was decreased. Weight loss, shrinkage and porosity of the pyrolized samples were investigated. Weight loss and shrinkage of the samples increased when increasing pyrolysis temperature while porosity decreased.

The Effects of Solvents on the Solvothermal Synthesis of BiVO4 Photocatalyst Powders

In this study, the effects of different solvents such as ethanol, ethylene glycol, glycerol on the preparation of BiVO4 via solvothermal process, and the influent of calcination heat treatment were studied. The crystal structure, surface area, morphology and optical properties of the obtained BiVO4 particles were investigated by means of X-ray Diffraction (XRD), Brunauer Emmett Teller method (BET), Scanning electron microscope (SEM) and UV-Vis reflectance spectroscopy (UV-Vis DRS), respectively. XRD patterns reveal that all of the obtained BiVO4 samples prepared by solvothermal at 130°C for 4 h have monoclinic structure. The UV-Vis DRS demonstrates that the band gaps of prepared BiVO4 are about 2.38-2.40 eV. The photocatalytic activity was evaluated by photo-degradation of rhodamine B (Rh B) solution under visible light irradiation (λ>420 nm). As the results, the BiVO4 prepared by using ethanol having high crystallinity and surface area showed the highest visible light photocatalytic activity compared to using glycerol and ethylene glycerol, respectively. Furthermore, the photocatalytic activity of BiVO4 prepared by using ethylene glycerol and glycerol could be enhanced by calcination heat treatment at 500°C for 2 h.

Fabrication of Zeolite Na-A and Activated Carbon Composites by Slip Casting for Drinking Water Filtration

Hybrid composite for drinking water filter aids were prepared by slip casting method. The slip was prepared from the mixture of 17.41% of zeolite Na-A, 17.41% of activated carbon, 0.35% of ZnO nanoparticles, 8.7% of phenolic resin, 0.54% carboxymethyl cellulose and 55.59% of reversed osmosis water. The slip was mixed in a high speed ball mill for 15, 30, 45 and 60 minutes and was then poured into plaster molds for 3 hours in order to maintain hollow casting. The green body was dried and fired at several of firing temperature of 600, 650, 700 and 750 °C. The major characteristics of the composite filter were characterized as: mechanical strength, morphology, pore diameter and ion exchange ability by three points bending, scanning electron microscopy (SEM), mercury porosimetry and inductive coupled plasma-optical emission spectroscopy (ICP-OES), respectively.

Effect of Alumina Source and Soaking Time on Properties of Refractory Mortar Using as Slumping Mold

Slumping molds or sagging molds are utilized for shaping glassware containers and many kinds of slumped glass products from glass plates. In Thailand, a large number of slumped glass factories use such molds in their production because slumping process is easy and cheap; however, the major cost of this process is slumping molds. They are imported from other countries and are expensive. In this research, slumping molds are created from local raw materials using the basic method to reduce the cost of the production. One of proper materials for making slumping mold is refractory mortar which can be easily formed into various shapes and sizes. Consequently, it is interesting to prepare slumping molds from refractory mortar. In this study, the effect of different sources of alumina (calcined alumina and aluminum sludge) and soaking time on the properties of the refractory mortar were investigated. Dolomite clay, milled sand and white portland cement were mixed with sources of alumina in distilled water to form pastes. Super plasticizer was added to the pastes to adjust flow ability. Plastic containers were used as molds for specimen forming. Specimens were cured at room temperature for 24 hours and dried in air for 24 hours. After that specimens were dried in an oven at 110 °C for 24 hours and then fired at 1100 °C. The result showed that the suitable condition for making slumping mold is to use calcined alumina as a source of alumina with soaking temperature of 1100 °C for 4 hours. The physical properties, chemical properties and thermal properties were discussed.

Fabrication of Silicon Carbide from Rice Husk by Carbothermal-Reduction and In Situ Reaction Bonding Technique

Silicon carbide (SiC) ceramics were prepared by carbothermal reduction together with in-situ reaction bonding. Raw rice husk was carbonized in an incineration furnace. The carbonized rice husk was ground and was then treated with hydrochloric acid by varying concentrations. The sample powders were mixed with silicon metal powder and pyrolyzed at various temperatures in either argon or nitrogen atmosphere. Silicon carbide phase was found in all pyrolyzed samples. Cristobalite was found in argon atmosphere pyrolyzed samples while silicon oxynitride was found in the samples pyrolyzed in nitrogen atmosphere at lower than 1500 °C. Silicon carbide whisker is the main phase on the surface of pyrolyzed sample. Increasing pyrolysis temperatures decreased the amount and size of silicon carbide whisker but increased the silicon carbide particle. Porosity and weight loss of samples after pyrolysis were increased with increasing temperatures due to the reaction in the system.