• Advances in environmental research
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• v.7 no.3
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• pp.213-223
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• 2018

Continuous input into the aquatic ecosystem and persistent structures have created concern of antibiotics, primarily due to the potential for the development of antimicrobial resistance. Degradation kinetics and mineralization of vancomycin B (VAN-B) by photocatalysis using $TiO_2$ and ZnO nanoparticles was monitored at natural pH conditions. Photocatalysis (PC) efficiency was followed by means of UV absorbance, total organic carbon (TOC), and HPLC results to better monitor degradation of VAN-B itself. Experiments were run for two initial VAN-B concentrations ($20-50mgL^{-1}$) and using two catalysts $TiO_2$ and ZnO at different concentrations (0.1 and $0.5gL^{-1}$) in a multi-lamp batch reactor system (200 mL water volume). Furthermore, a set of toxicity tests with Daphnia magna was performed to evaluate the potential toxicity of oxidation by-products of VAN-B. Formation of intermediates such as chlorides and nitrates were monitored. A rapid VAN-B degradation was observed in ZnO-PC system (85% to 70% at 10 min), while total mineralization was observed to be relatively slower than $TiO_2-PC$ system (59% to 73% at 90 min). Treatment efficiency and mechanism of degradation directly affected the rate of transformation and by-products formation that gave rise to toxicity in the treated samples.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.433-438
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• 2016

The current study evaluated the air quality of the smoking booth equipped with the air purification system consisting of photocatalysts and air filters by measuring the concentrations of hazardous substances of tobacco smoke such as CO, HCHO, $CH_3CHO$, PM10 and PM2.5. To enhance the removal efficiency of hazardous substances, an infrared ray was exposed to improve the reactivity of OH radical generated from the photocatalyst toward environmental tobacco smoke (ETS) gas phase hazardous materials. It was found that the smoking booth with the air purification system improved the removal efficiency of hazardous substances containing formaldehyde by 85.2% compared to that of the smoking booth without any purification systems. In addition, the removal efficiency of the fine dust after treatment was enhanced up to 89.4%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.154-157
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• 2003

$TiO_2$ thin films were fabricated by RF magnetron sputtering system at by controlling deposition times, ratios of $Ar:O_2$ partial presser ratio and substrate conditions. And the surface, cross-section morphology, microstructure, and composition ratio of the films were analyzed by FE-SEM, TEM and XPS. Besides, the optical absorption and transmittance of the $TiO_2$ films were measured by a UV-VIS-NIR Spectrophotometer, and photocatalytic properties were studied by G${\cdot}$C Analyzer & Data Analysis system. As the result, when $TiO_2$ thin film was made at deposition time of 120[min] and $Ar:O_2$ ratio of 60:40, the best structural and optical properties among many thin films could be accepted. The best results of properties were as follows: thickness; 360~370[nm), grain size; 40[nm], gap between two peak binding energy; $5.8{\pm}0.05[eV]$ ($2_{p3/2}$ peak and $2_{p1/2}$ peak of Ti was show at $458.3{\pm}0.05[eV]$ and $464.1{\pm}0.05[eV]$ respectively), binding energy; $530{\pm}0.05[eV]$, optical energy band gap; 3.4[eV].

• Journal of the Korean Society of Food Culture
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• v.32 no.3
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• pp.227-234
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• 2017

This study attempted to establish the optimal conditions for storage of spring kimchi cabbage to stably control supply and demand. To this end, this study stored kimchi cabbages in various manners for different periods and compared the quality characteristics of kimchi using these cabbages. According to the results, pre-drying with photocatalytic and pre-cooling treatments showed average selectivity loss rates of 18.83 and 21.37%, respectively, which were lower than those of other treatments. Spring kimchi cabbages were stored for 15 weeks under various conditions, and the kimchi was stored for 4 weeks at $4^{\circ}C$. After ripening, each kimchi was analyzed for their soluble solid content, pH, acidity, and salinity. The average pH of kimchi was 4.60 and tended to rise, whereas average acidity was 0.38% and fell by 0.24 to 0.31% as the storage period was extended. Extension of the storage period caused decreases in soluble solid content and salinity, and the number of lactic acid bacteria decreased due to increased pH and reduced acidity (p<0.05). Sensory evaluation showed that all experts and non-professionals preferred kimchi treated by precooling compared to any other treatment.

• Journal of Environmental Science International
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• v.9 no.2
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• pp.151-158
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• 2000

Considerable interest has been shown in recent years towards utilizing $TiO_2$ particles as a photocatalyst in the degradation of harmful organic contaminants. In this study, photocatalytic degradation of diazinon which is extensively used as a pesticide in the agriculture field, has been investigated with UV-illuminated $TiO_2$ weight, UV wavelength, pH of the solution. Photodegradation rate increased with decreasing initial concentration of diazinon and with increasing pH of the solution. Photodegradation rate increased with increasing $TiO_2$ weight, but was nearly the same at $TiO_2$ weight of 1g/$\ell$, 2 g/$\ell$, i.e., for initial diazinon concentratin of 5 mg/$\ell$. UV wavelength affecting on the degradation rate of diazinon decreased in the order of 254 nm>312 nm> 365 nm. For $TiO_2$ weight of 1 g/$\ell$and initial diazinon concentration of 5 mg/$\ell$, the photodegradation removal of diazinon was 100% after 130 min in the case of 254 nm, but 95% in the case of 312 nm, and 84% in the case of 365nm, after 180 min. The photodegradation of diazinon followed a first order or a pseudo - first order reaction rate. For initial diazinon concentration of 5 mg/$\ell$, the rate constants(k) in UV and $TiO_2$(1 g/$\ell$)/UV system were $0.006 min^{-1} and 0.0252 min^{-1} at 254 nm, 0.0055 min^{-1} and 0.0104 min^{-1} at 312 nm, and 0.004 min^{-1}$ at 365 nm respectively.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2295-2298
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• 2014

To effectively destruct 2-chlorophenol, a representative sterile preservative, nanometer-sized Mn (0.5, 1.0, 3.0 mol %)-incorporated $TiO_2$ powders were synthesized by a solvothermal method. XRD result demonstrated that the Mn ingredients were perfectly inserted into $TiO_2$ framework. The Mn-$TiO_2$ particles exhibited an anatase structure with a particle size of below 20 nm. The absorbance was shifted to the higher wavelength on Mn-$TiO_2$ compared to that of $TiO_2$. Otherwise, the PL intensities which has a close relationship for recombination between holes and electrons significantly decreased on Mn-$TiO_2$. The photodecomposition for 2-chlorophenol in a liquid system was enhanced over Mn-doped $TiO_2$ compared with pure $TiO_2$: 2-chlorophenol of 50 ppm was completely decomposed after 12 h when 1.0 mol % Mn-$TiO_2$ was used. Consequently, the core of this paper is as follows. introducing Mn into $TiO_2$ framework reduced the band-gap, moreover, it played as an electron capture resulted to lower recombination between electrons and holes during photocatalytic reaction for removal of 2-cholophenol.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.5
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• pp.512-522
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• 2008

Ammonia is a major compound of odor in livestock house. To enhance the performance of ammonia oxidation (decomposition). the gas-liquid, two phase photocatalytic oxidation system was designed and prepared in this study. Commercial P-25 as $TiO_2$ catalyst was used for ammonia decomposition. V/P-25 catalyst prepared by sol gel method was also used for the removal of by-producted $NO_x$ in $NH_3$ oxidation reaction. When $TiO_2$ was used as a photocatalyst, the conversion to $N_2$ in ammonia decomposition reached above 90% until 200hr (The air flow rate of 4L/min with the ammonia concentration up to 25ppm.). However, considerable amounts of NO and $NO_2$ were formed as a result of $NH_3$ oxidation (as a by-product). Therefore, we added Vanadia impregnated $TiO_2$(P-25) catalyst for the removal of $NO_x$ at the end of reaction trail. The results of a pilot-scale operation were successful to achieve the simultaneous removal of $NH_3\;and\;NO_x$ about 81 and 87%, respectively.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E1
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• pp.19-26
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• 2006

The decomposition of gaseous $CH_3CHO$ was investigated by metal loaded $TiO_2$ (pure $TiO_2,\;Pt/TiO_2,\;Pd/TiO_2,\;Mn/TiO_2\;and\;Ag/TiO_2$) with $UV/TiO_2$ process and $UV/TiO_2/O_3$ process at room temperature and atmospheric pressure. Metal loaded $TiO_2$ was prepared by photodeposition. Decomposition of $CH_3CHO$ was carried out in a flow-type photochemical reaction system using three 10W black light lamps ($300{\sim}400nm$) as a light source. The experimental results showed that the degradation rate of $CH_3CHO$ was increased with Pt and Ag on $TiO_2$ compared to pure $TiO_2$, but decreased with depositing Pd and Mn on pure $TiO_2$. The considerable increase in the degradation efficiency of the $CH_3CHO$ was found by a combination of photocatalysis and ozonation as compared to only by ozonation or photocatalysis. Loading of Pt on $TiO_2$ promoted conversion of gaseous ozone. The degradation rate of gaseous $CH_3CHO$ decreased with an increase of water vapor in the feed stream for the both $UV/TiO_2\;and\;UV/TiO_2/O_3$ processes. The pure $TiO_2$ was more affected by the water vapor than Pt loaded $TiO_2$.

• Journal of Microbiology and Biotechnology
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• v.28 no.6
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• pp.957-967
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• 2018

A novel $g-C_3N_4$/ZnO/stellerite (CNZOS) hybrid photocatalyst, which was synthesized by coupled hydro thermal-thermal polymerization processing, was applied as an efficient visible-light-driven photocatalyst against Staphylococcus aureus. The optimum synthesized hybrid photocatalyst showed a sandwich structure morphology with layered $g-C_3N_4$ (doping amount: 40 wt%) deposited onto micron-sized ZnO/stellerite particles (ZnO average diameter: ~18 nm). It had a narrowing band gap (2.48 eV) and enlarged specific surface area ($23.05m^2/g$). The semiconductor heterojunction effect from ZnO to $g-C_3N_4$ leads to intensive absorption of the visible region and rapid separation of the photogenerated electron-hole pairs. In this study, CNZOS showed better photocatalytic disinfection efficiency than $g-C_3N_4/ZnO$ powders. The disinfection mechanism was systematically investigated by scavenger-quenching methods, indicating the important role of $H_2O_2$ in both systems. Furthermore, $h^+$ was demonstrated as another important radical in oxidative inactivation of the CNZOS system. In respect of the great disinfection efficiency and practicability, the CNZOS heterojunction photocatalyst may offer many disinfection applications.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.101-107
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• 1999

$TiO_2$ and $xTiO_2-ySiO_2$ system photocatalysts were developed by sol-gel method based on the change of production parameters, and their structure of crystallization and the specific surface area was measured. Considering the efficiency of the ethanol decomposition using the catalyst, the conclusion was made as follows: 1) By means of X-ray analysis of $TiO_2$ powder that is obtained from water and Titanium alkoxide with various molar ratios, it is shown that structure of crystallization is a dominating structure and, on the other hand, the crystallization of rutile also partly exists. The specific surface area is at its maximum value at R=6, which is the molar ratio of water vs. alkoxide, whereas its value goes down as the molar ratio increases. In the reaction of using $TiO_2$ catalyst, the ethanol is decomposed into the extent of 15 ~30% in an hour and three hours are necessitated for 70% decomposition. 2) $TiO_2/SiO_2$ powder is developed from Titanium and Silicon alkoxide by a hetero-condensation process. The increase of SiO$_2$ contents causes the decrease of the degree of crystallization of the gel, whereas the specific surface area preferentially increases. In the decomposition reaction of the ethanol, the decomposition efficiency represents 25~60% in an hour. It is, however, examined that the efficiency inactively increases corresponding to the duration of reaction time. It is shown that more than 90% of ethanol is decomposed when reaction time is about three hours and the efficiency illustrates the maximum value for 60-$TiO_2/4O-SiO_2$ catalyst.