Hyun Jong Kim

Preparation of mesoporous silica fiber matrix for VOC removal

Abstract A novel method for the preparation of the mesoporous silica fiber matrix was introduced for a removal of volatile organic compounds (VOCs). Paper making technology was applied to make a sheet of mesoporous silica fiber matrix. Reinforcing the mesoporous silica fiber with the ceramic fibers (50xa0wt.%) increased the mechanical strength of the matrix. Mesoporous silica fibers using TMOS (tetramethoxysilane) as a silica source and CTAC (cetyltrimethyl-ammoniumchloride) as a surfactant were drawn by the spinning method. The spinning process increased both the crystallinity and the fraction of mesopores (1.9xa0nm) of the fiber. As the spinning rate was increased both the crystallinity and the specific area of the mesoporous silica fiber increased, but the diameter of fiber decreased. We could control the size and morphology of mesoporous silica fiber matrix by changing the shape of substrates. This leads to easy fabrication of honeycomb-structured adsorbent which can be used for the VOC removal.

Photocatalytic characteristics of TiO2 supported on SiO2

The photocatalytic decomposition of acetaldehyde was carried out on TiO2/SiO2. The presence of a support (SiO2) in TiO2/SiO2 helped to promote the efficiency of the photocatalyst. The silica support enhanced the effective surface area of TiO2 and adsorption of acetaldehyde on TiO2/SiO2. TiO2/SiO2 synthesized from Ti(SO4)2 showed promoting effect on acetaldehyde decomposition. The XPS results revealed that TiO2/SiO2 prepared with Ti(SO4)2 generated SO42− sites on the TiO2 surface. The increased acidity could promote the adsorption of acetaldehyde and photocatalytic degradation of acetaldehyde. The sulfate ion seemed to generate the bifunctional sites (acid sites and photoactive sites) and promoted the acetaldehyde decomposition on TiO2/SiO2.

Photocatalytic activity of metal ion (Fe or W) doped titania

Iron or tungsten-doped nano TiO2 were successfully synthesized from TiCl4. All of the samples showed anatase phase of TiO2. For the iron-doped TiO2, Iron ion was well dispersed in the TiO2 lattice. However, tungsten-doped TiO2 formed 12-tungstate with anatase TiO2. As the concentration of tungsten increased, 12-tungstate disappeared. The photocatalytic oxidation of acetaldehyde was evaluated to examine the photocatalytic characteristics of metal-doped TiO2. Because of the surface containing metal oxide or metal precursors at high concentration metal ion, increasing the concentration of W or Fe ion decreased the reactivity. The reaction rate was drastically increased after 300 °C heat treatment. Furthermore, the photocatalytic activity of iron- or tungsten-doped TiO2 was higher than that of synthesized pure TiO2 and commercial TiO2.

Preparation of TiO2 fiber and its photocatalytic properties

TiO 2 fibers were successfully synthesized by ACF template method. The structural and electronic properties were examined by using FE-SEM, TG/DTA, XRD, BET, EDX and XPS spectroscopy. TiO 2 fiber has a uniform diameter of 5-10 μm and rough surface. Ti precursor, ratio of Ti/ACF in preparation step and calcinations temperature of TiO 2 fibers were optimized for the photocatalytic application. The TiO 2 fiber which was prepared by using 15% Ti(SO 4 ) 2 /ACF solution and calcined at 773K showed the highest photocatalytic activity for the decomposition of acetaldehyde. The photocatalytic performance of TiO 2 fiber was higher than the commercial TiO 2 (Degussa P-25) because of its large surface area, high crystallinity and acid sites.

Preparation of Heteropoly Acid Entraped in Nano Silica Matrix

Abstract Heteropoly acid entraped in nano silica matrix was prepared by the microemulsions method. The primary particle size was less than 400nm and it decreased with the content of the heteropoly acid. When these silica particles were blended with sulfonated polyethersulfone, the HPA could be effectively immobilized in aqueous environment. The conductivity of this composite electrolyte was 1.4×10−3 S/cm with the 15% HPA.

Performance of ceramic composite membrane for the separation of VOCs

Zeolite composite membranes were prepared for the separation of VOCs by the pressurized coating method. On the top of the composite membrane, TiO2, polyimide or polyethersulfone were coated by the same tech-100 nm-sized nique.ZSM-5 coated membranes show higher selectivity for n-hexane in n-hexane/benzene mixture than 500 nm sized ZSM-5 coated membrane. Composite membrane coated with 100 nm zeolite and polymer showed the highest selectivity (44) for n-hexane/benzene.

The Photodecomposition of Acetaldehyde in Gas Phase Using Immobilized TiO2 on Porous α-Al2O3 Tube

Abstracts A study on the photocatalytic degradation of acetaldehyde using immobilized TiO2 on porous α- Al2O3 tube was performed. Among various TiO2-immobilization methods such as a sol-gel and a suspension coating, suspension coating method (method B) showed the highest photodecomposition rate of acetaldehyde, and the most effective coating thickness of TiO2 layer in method B was about 10 μm. Apparently, all reactions followed 1st order kinetics and the temperature did not affect the photodecomposition of acetaldehyde in the range of 25 ~ 70 °C. As far as oxidants were concerned, O2 revealed a positive effect on the photooxidation, but H2O behaved in a opposite way. Platinum loading on immobilized TiO2 on Al2O3 tube by using photoreduction enhanced the photocatalytic reaction rate of acetaldehyde.