• Membrane Journal
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• v.4 no.3
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• pp.152-162
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• 1994

The photodegradation efficiency of formic acid on $TiO_2$ photocatalytic membranes was investigated. A new titania membrane reactors for purification of water combining microfiltration with photocatalytic degradation of organic compounds were developed. Titania membrane tubes(average pore size of $0.2\mu m$) were prepared by the slip casting, and porous thin films of $TiO_2$ were formed on the tube surface by the sol-gel process to increase the surface area, and consequently to increase photodegradation efficiency of organic compounds. The UV light with the wavelength of 365 nm was used as a light source for photocatalytic reactions. The photodegradation efficiency of the organic compounds was strongly dependent on the flux of the solution, the microstructure of the membrane (sol pH), and the amount of $O_2$ supplied. The effects of the primary oxidant such as $H_2O_2$ and dopants such as $Nb_2O_5$ on the photodegradation efficiency were also investigated. The results showed that more than 80% of formic acid could be degraded using membrane coated with a $TiO_2$ sol of pH 1.45. The photodegradation efficiency could be improved by about 20% when adding $H_2O_2$ in feed solution or doping $TiO_2$ membranes with $Fe_2O_3$.

• Membrane Journal
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• v.18 no.1
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• pp.35-43
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• 2008

In this study, we tried to solve membrane fouling with membranes made by fine nano-particle in MBR process. And we confirmed good fouling resistance in pilot test. In this test, we confirmed our membrane with titania out-standing quality by testing in the pilot long-term test by comparing to other company product. Our membrane keep up steadily $20{\sim}25 L/m^2{\cdot}hr$ high flux in $7,000{\sim}13,000mg/L$ MLSS high sludge concentration. In addition to this quality, we studied membrane flux character related membrane arrangement, membrane-air line arrangement, air-line hole size, cleaning solution concentration, treatment method, etc. Using the optimization of this additional parameter, we tried to search method of maximizing membrane quality.

• Journal of Hydrogen and New Energy
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• v.18 no.2
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• pp.151-156
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• 2007

Solar cell and nanofiltration membrane were utilized in a system of enzymatic hydrogen production through light-sensitized photoanode, which resembles photoelectrochemical(PEC) configuration. Solar cell uses no additional light energy to increase energy for electrons to reduce protons and for holes to oxidize water to oxygen, and nanofiltration membrane replaces a salt bridge successfully with increased ion transport capability. With this system configuration, optimized amount of enzyme(10.98 unit), and an anodized tubular $TiO_2$ electrode($5^{\circ}C$/1 hr in 0.5 wt% HF-$650^{\circ}C$/5 hr) hydrogen evolved at a rate of ca. $43\;{\mu}mol/(cm^2{\times}hr)$ in a cathodic compartment and oxygen generated at a rate of ca. $20\;{\mu}mol/(cm^2{\times}hr)$ in an anodic compartment. The stoichiometric evolution of gases indicated that water was splitted in the system.

• Journal of the Korean Ceramic Society
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• v.29 no.5
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• pp.403-409
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• 1992

The titania membrane thickness coated on the porous alumina support by the sol-gel method was analyzed using the slipcasting model. The thickness of calcined membrane layers increased linearly from 1.3 to 3.8 ${\mu}{\textrm}{m}$ with the square root of the dipping time (4~40 min). Growth rates of the thickness of wet gels and calcined layers were well described quantitatively by the slipcasting model. Through the regression of experimental data using model equations, the permeability and the pressure drop across wet gels, and the thickness and their growth rate constants of wet gels and calcined layers could be determined. It was also known that the gellation concentration of the TiO2 sol used in this work and the porosity of wet gel layes were 25 mol/ι and 0.53, respectively.

• Journal of the Korean Ceramic Society
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• v.53 no.3
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• pp.325-331
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• 2016

Anatase particles of titanium dioxide were prepared from $TiCl_4$ aqueous solution by using an electro-dialysis [ED] process. For the preparation of an aqueous solution of $TiCl_4$ precipitates, $TiCl_4$ liquid frozen in ice was transferred to a neck flask and then hydrolyzed using deionized [DI] $H_2O$. During the hydrolysis of the $TiCl_4$ solution at $0^{\circ}C$, a slurry solution of $TiOCl_2$ was obtained and the color changed from red to orange. The ED process was applied for the removal of chlorine content in the slurry solution. Two kinds of hydrolyzed slurry solution with lower [$Ti^{4+}$] and higher [$Ti^{4+}$] were sampled and the ED process was applied for the samples according to the removal time of [$Cl^-$]. With de-chlorination, the solution status changed from sol to gel and the color quickly changed to blue. Finally, white crystalline powders were formed and the phase was confirmed by XRD to be anatase crystallites. The morphology of the hydrous titania particles in the solution was observed by FE-SEM. The hydrous titania particles were nano-crystalline, and easily coagulated with drying.

• Membrane and Water Treatment
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• v.10 no.3
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• pp.223-229
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• 2019

Titania modified by 2-ethylimidazole (2-EI) (denoted as $2-EI-TiO_2$) demonstrated visible light photocatalytic activity for the degradation of organic compounds. $2-EI-TiO_2$ was a bright brown powder that exhibited similar crystallinity and morphology with the control $TiO_2$. A diffuse reflectance spectrum indicated that $2-EI-TiO_2$ absorbs visible light of all wavelengths. X-ray photoelectron spectroscopy (XPS) confirmed the cationic state of nitrogen species (e.g. Ti-O-N) on the surface of $2-EI-TiO_2$. Visible light-illuminated $2-EI-TiO_2$ degraded $10{\mu}M$ 4-chlorophenol (4-CP) by approximately 85% in 4 h. The photochemical activity of $2-EI-TiO_2$ was selective in targeting the organic compound. The repeated use of $2-EI-TiO_2$ decreased the photocatalytic activity for the 4-CP degradation. Experiments using radical scavengers and oxidant probes revealed that the oxidation by photogenerated holes is responsible for the degradation of organic compounds by illuminated $2-EI-TiO_2$ and the role of $^{\bullet}OH$ is negligible.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.8.1-8.1
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• 2011

Nanocrystalline titanium dioxide ($TiO_2$) materials have been widely used as an electron collector in DSSC. This is required to have an extremely high porosity and surface area such that the dye can be sufficiently adsorbed and be electronically interconnected, resulting in the generation of a high photocurrent within cells. In particular, their geometrical structures and crystalline phase have been extensively investigated as important issues in improving its photovoltaic efficiency. In this study, we present a new strategy to fabricate a photoelectrode having a periodic structured $TiO_2$ film templated from 1D or 3D polystyrene (PS) microspheres array. Monodisperse PS spheres of various radiuses were used for colloidal array on FTO glasses and two types of photoelectrode structures with different $TiO_2$ materials were investigated respectively. One is the igloo-shaped electrode prepared by $TiO_2$ deposition by RF-sputtering onto 2D microsphere-templated substrates. At the interface between the film and substrate, there are voids formed by the decomposition of PS microspheres during the calcination step. These holes might be expected to play the predominant roles as scattering spherical voids to promote a light harvesting effect, a spacious structure for electrolytes with higher viscosity and effective paths for electron transfer. Additionally the nanocrystalline $TiO_2$ phase prepared by the RF-sputtering method was previously reported to improve the electron drift mobility within $TiO_2$ electrodes. This yields solar cells with a cell efficiency of 2.45% or more at AM 1.5 illumination, which is a very remarkable result, considering its $TiO_2$ electrode thickness (<2 ${\mu}m$). This study can be expanded to obtain higher cell efficiency by higher dye loading through the increase of surface area or multi-layered stacking. The other is the inverse opal photonic crystal electrode prepared by titania particles infusion within 3D colloidal arrays. To obtain the enlargement of ordered area and high quality of crystallinity, the synthesis of titania particles coated with a organic thin layer were applied instead of sol-gel process using the $TiO_2$ precursors. They were dispersed so well in most solvents without aggregates and infused successfully within colloidal array structures. This ordered mesoporous structure provides the large surface area leading to the enough adsorption of dye molecules and have an light harvesting effect due to the photonic band gap properties (back-and-forth reflection effects within structures). A major advantage of this colloidal array template method is that the pore size and its distribution within $TiO_2$ photoelectrodes are determined by those of latex beads, which can be controlled easily. These materials may have promising potentials for future applications of membrane, sensor and so on as well as solar cells.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.131-136
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• 2008

Silica- or titania-filled poly (vinylidene fluoride-co-hexafluoropropylene)-based polymer electrolytes were prepared by phase inversion technique using N-methyl-2-pyrrolidone and dimethyl acetamide as solvent and water as non-solvent. The polymer electrolytes were adopted to the lithium metal polymer battery using high-capacity cathode $Li[Ni_{0.15}Co_{0.10}Li_{0.20}Mn_{0.55}]O_2$ and lithium metal anode. After the repeated charge-discharge test for the cell, it was proved that the cell adopting the polymer electrolyte based on the phase-inversion membrane containing 40~50 wt% silica showed the highest discharge capacity (180 mAh/g) until 80th cycle and then abrupt capacity fade was just followed. The capacity fade might be due to the deposition of lithium dendrite on the polymer electrolyte, in which the capacity retention was no longer sustainable.