• Journal of Environmental Science International
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• v.16 no.7
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• pp.785-791
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• 2007

The current study evaluated the technical feasibility of the application of titanium dioxide ($TiO_{2}$) photo-catalytic air cleaners for the disinfection of bioaerosols present in indoor air. The evaluation included both laboratory and field tests and the tests of hydraulic diameter (HD) and lamp type (LT). Disinfection efficiency of photocatalytic oxidation (PCO) technique was estimated by survival ratio of bacteria or fungi calculated from the number of viable cells which form colonies on the nutrient agar plates. It was suggested that the reactor coating with $TiO_{2}$ did not enhance the adsorption of bioaerosols, and that the UV irradiation has certain extent of disinfection efficiency. The disinfection efficiency increased as HD decreased, most likely due to the decrease in the light intensity since the distance of the catalyst from the light source increased when increasing the HD. It was further suggested that the mass transfer effects were not as important as the light intensity effects on the PCO disinfection efficiency of bioaerosols. Germicidal lamp was superior to the black lamp for the disinfection of airborne bacteria and fungi, which is supported by the finding that the disinfection efficiencies were higher when the germicidal lamp was used compared to the black lamp in the laboratory test. These findings, combined with operational attributes such as a low pressure drop across the reactor and ambient temperature operation, can make the PCO reactor a possible tool in the effort to improve indoor bioaerosol levels.

• Bulletin of the Korean Chemical Society
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• v.28 no.11
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• pp.1951-1957
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• 2007

A new synthetic strategy based on the acid-base catalyzed sol-gel method was developed for the preparation of a series of mesoporous TiO2 nanoparticles. A key feature of the method involves a gradual change in pH (0.8- 9) during the sol-gel transition, which guarantees easy introduction of mesoporosity without relying on the well-established sonochemical or template approach. In addition, this method leads to the exclusive formation of the anatase phase stable enough to the calcination temperature up to 600 oC. The physicochemical properties of the particles in the series were characterized by various spectroscopic and analytical techniques such as wide-angle XRD, SAXRD, BET surface area, FE-SEM, TEM, FT-IR, TGA, and XPS. The photocatalytic efficiency of these materials was investigated for the oxidation of toluene under UV-irradiation. All but T-ad in the series exhibited high photocatalytic activity pushing the reaction into completion within 3 h. The reaction followed the first order kinetics, and the rate reaches as high as 3.9 × 10?2/min which exceeds the one with the commercially available Degussa P-25 by a factor of 3.2. When comparison is made among the catalysts, the reactivity increases with increase in the calcination temperature which in turn increases the crystallinity of the anatase phase, thus revealing the following rate orders: T-3 < T-4 < T-5 < T-6.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.297-302
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• 2013

Enhancement of photocatalytic activity of UV/photocatalysis was carried out to oxidize the gaseous $H_2S$ in a tubular reactor coated with photocatalyst of sol type $TiO_2$. EtOH was used as the standard material to select the photocatalyst, and it was confirmed that the reactor activity was dependent on the coated surface characteristics. The selected photocatalytic reactor, which coated with STS-01, showed about 80% conversion when the gas linear velocity was 0.01 m/s and relative humidity was 40%. However, the conversion level of the reaction decreased significantly with increasing gas linear velocity. Pt was loaded on the photocatalyst to enhance and maintain the performance of the reactor, which enhanced the conversion level of $H_2S$ more than 95% under the same experimental condition.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.41-46
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• 2014

The property improvement of polycarbonate coated with a multilayer film composed of an inorganic $SiO_2$ film and a photocatalytic $TiO_2$ film was studied. The $SiO_2$ film as a binder had an excellent light transmission characteristic. After the treatment with atmospheric pressure plasma, the surface of $SiO_2$ film showed the hydrophilicity, which increased the film coating uniformity with a $TiO_2$-containing aqueous solution. When $TiO_2$ film was over 200 nm thick, the absorption effect of UV rays in the range of 180~400 nm suppressed the yellowing phenomena of polycarbonate substrate. The inorganic film improved the heat resistance of polycarbonate substrates. $TiO_2$ film in the outmost under the exposure of UV rays promotes the catalytic oxidation characteristics and yields the capability to the decomposition of organic contaminants, and also increases the self-cleaning properties due to the increase of hydrophilicity. Structural stability of the polycarbonate substrate coated with inorganic $TiO_2$ and $SiO_2$ film was shown. The role of $SiO_2$ film between $TiO_2$ and polycarbonate substrate suppressed the peeling of $TiO_2$ film by inhibiting the photocatalytic oxidation effect of $TiO_2$ film on the polycarbonate substrate.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.697-705
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• 2011

The aim of this study was to examine ozonation disinfection efficiency for Escherichia coli DH5alpha removal, containing the multi-resistance plasmid pB10 as well as chlorination disinfection efficiency. In addition, plasmid pB10 removal rates were estimated by ozonation and chlorination. The removal efficiency of pB10 via ozonation was about 2 to 4 times higher than chlorination. High removal efficiency of pB10 is likely due to OH radical produced during ozonation. These results suggest that integration of advanced oxidation process such as ozonation (or photocatalytic oxidation) with conventional disinfection such as chlorination may be needed for effective control of antibiotic resistant bacteria and genetic materials.

• Journal of Environmental Science International
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• v.17 no.9
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• pp.1023-1032
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• 2008

The feasibility study of the application of the photoelectrocatalytic and electrolytic/UV decolorization of Rhodamine B (RhB) was investigated in the photoelectrocatalytic and electrolytic/UV process with $TiO_2$ photoelectrode and DSA (dimensionally stable anode) electrode. Three types of $TiO_2$ photoelectrode were used. Thermal oxidation electrode (Th-$TiO_2$) was made by oxidation of titanium metal sheet; sol-gel electrode (5G-$TiO_2$) and powder electrode (P-$TiO_2$) were made by coating and then heating a layer of titania sol-gel and slurry $TiO_2$ on titanium sheet. DSA electrodes were Ti and Ru/Ti electrode. The relative performance for RhB decolorization of each of the photoelecoodes and DSA electrodes is: Ru/Ti > Ti > SG-$TiO_2$ > Th-$TiO_2$. It was observed that photoelectrocatalytic decolorization of RhB is similar to the sum of the photocatalytic and electrolytic decolorization. Therefore the synergetic effect was not showed in pthotoelectrocatalytic reaction. $Na_{2}SO_{4}$ and NaCl showed different decolorization effect between pthotoelectrocatalytic and electrolytic/UV reaction. In the presence of the NaCl, RhB decolorization of Ru/Ti DSA electrode was higher than that of the other photoelectrode and Ti electrode. Optimum current, NaCl dosage and UV lamp power of the electrolytic/UV process (using Ru/Ti electrode) were 0.75 A, 0.5 g/L and 16 W, respectively.

• Korean Journal of Materials Research
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• v.19 no.9
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• pp.481-487
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• 2009

The photocatalysts of Fe-ACF/$TiO_2$ compositeswere prepared by the sol-gel method and characterized by BET, XRD, SEM, and EDX. It showed that the BET surface area was related to adsorption capacity for each composite. The SEM results showed that ferric compound and titanium dioxide were distributed on the surfaces of ACF. The XRD results showed that Fe-ACF/$TiO_2$ composite only contained an anatase structure with a Fe mediated compound. EDX results showed the presence of C, O, and Ti with Fe peaks in Fe-ACF/$TiO_2$ composites. From the photocataytic degradation effect, $TiO_2$ on activated carbon fiber surface modified with Fe (Fe-ACF/$TiO_2$) could work in the photo-Fenton process. It was revealed that the photo-Fenton reaction gives considerable photocatalytic ability for the decomposition of methylene blue (MB) compared to non-treated ACF/$TiO_2$, and the photo-Fenton reaction was improved by the addition of $H_2O_2$. It was proved that the decomposition of MB under UV (365 nm) irradiation in the presence of $H_2O_2$ predominantly accelerated the oxidation of $Fe^{2+}$ to $Fe^{3+}$ and produced a high concentration of OH radicals.

• Advances in environmental research
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• v.3 no.1
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• pp.29-43
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• 2014

Pharmaceutical wastewater effluents are well known for their difficult elimination by traditional biotreatment methods and their important contribution to environmental pollution due to its fluctuating and recalcitrant nature. OTC is one of the nonbiodegradable antibiotics that makes antibiotic-resistant, so it can make be high risk for environment. NZVI can be a good choice for removal of OTC in aqueous solution. Response surface methodology (RSM) was used to optimize the amounts of NZVI and OTC to be used at pH 3 and under 200 W, UV-A irradiation. The responses were removal percent of absorption at 290 and 348 nm, TOC and COD of OTC. In the optimum condition, Linear model was performed 155 ppm of OTC were removed by 1000 ppm NZVI after 6.5 hours and the removal efficiency of absorption at 290 and 348 nm, TOC and COD were 87, 95, 85 and 89 percent, respectively. In the similar process, there is no organic compound after 14 hours. The parameters ORP, DO and pH were investigated for 6:30 hours to study the type of NZVI reaction in process. In the beginning of reaction, oxidation was the dominant reaction after 3 hours, photocatalytic reaction was remarkable. The mechanism of OTC degradation is proposed by HPLC/ESI-MS and four by products were found. Also the rate constants (first order kinetic chain reaction model) were 0.0099, 0.0021, 0.0010, 0.0049 and $0.0074min^{-1}$, respectively.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.3
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• pp.411-419
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• 2004

Titania particles are widely used as a photocatalyst to treat various contaminants in air and water. Titania particles were formed by vapor-phase oxidation of titanium tetraisopropoxide (TTIP) in a tube furnace between 773 and 1,273 K. The effect of process variables such as furnace temperature, flow rate of carrier air, and flow rate of sheath air on powder size and phase characteristics was investigated using a scanning mobility particle sizer (SMPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The size distribution of synthesized titania particles was characterized with mode diameter and peak concentration. The mode diameter ranging from 20 to 80 nm decreased with increasing flow rates of sheath air and carrier air, and increased with increasing furnace temperature. The peak concentration increased with increasing flow rates of sheath air and carrier air The best synthetic condition for high production rate can be derived from the experimental data set represented by mode diameter and peak concentration. The crystal structure of synthesized titania particles was found to be anatase phase, ensuring high photocatalytic potential.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.307-311
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• 2014

ZnS and $ZnS/TiO_2$ were prepared by chemical deposition. The prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM). The generation of reactive oxygen species was detected by monitoring the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). Excellent catalytic degradation of methylene blue (MB) solution was observed using the $ZnS/TiO_2$ composites during irradiation with visible light. The results show that the photocatalytic performance of $TiO_2$ nanoparticles is improved by loading with ZnS.