• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.148-154
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• 2007

This study was performed to evaluate the application of $TiO_2$ on the photocatalytic treatment of swine wastewater. $TiO_2$ sol was prepared by hydrothermal method with the agent ratio($(C_2H_5)_2NH_2\;mol/Ti(OC_3H_7)_4\;mol)=1$ and R ratio ($H_2O\;mol/Ti(OC_3H_7)_4\;mol)=42$. The effect of parameter on the removal efficiency of swine wastewater in a batch type immobilized photocatalyst system such as initial pH, intensity of UV, dosage of $TiO_2$, air flow rate, and concentration of $H_2O_2$ was examined. Wastewater was effectively eliminated in the presence of both UV light illumination and $TiO_2$. Photocatalytic activity was higher in acidic condition compared to neutral and alkaline conditions. In addition, photocatalytic activity increased with increasing UV light intensity, dosage of $TiO_2$, the flow rate of air and the amount of $H_2O_2$ added as an oxidant, but the excess amount of $H_2O_2$ dosage decreased the removal efficiency.

• Journal of Environmental Science International
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• v.19 no.12
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• pp.1323-1334
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• 2010

The effect of nitric oxide (NO) on antioxidant system and protective mechanism against oxidative stress under UV-B radiation was investigated in leaves of maize (Zea mays L.) seedlings during 3 days growth period. UV-B irradiation caused a decrease of leaf biomass including leaf length, width and weight during growth. Application of NO donor, sodium nitroprusside (SNP), significantly alleviated UV-B stress induced growth suppression. NO donor permitted the survival of more green leaf tissue preventing chlorophyll content reduction and of higher quantum yield for photosystem II than in non-treated controls under UV-B stress, suggesting that NO has protective effect on chloroplast membrane in maize leaves. Flavonoids and anthocyanin, UV-B absorbing compounds, were significantly accumulated in the maize leaves upon UV-B exposure. Moreover, the increase of these compounds was intensified in the NO treated seedlings. UV-B treatment resulted in lipid peroxidation and induced accumulation of hydrogen peroxide ($H_2O_2$) in maize leaves, while NO donor prevented UV-B induced increase in the contents of malondialdehyde (MDA) and $H_2O_2$. These results demonstrate that NO serves as antioxidant agent able to scavenge $H_2O_2$ to protect plant cells from oxidative damage. The activities of two antioxidant enzymes that scavenge reactive oxygen species, catalase (CAT) and ascorbate peroxidase (APX) in maize leaves in the presence of NO donor under UV-B stress were higher than those under UV-B stress alone. Application of 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3- oxide (PTIO), a specific NO scavenger, to the maize leaves arrested NO donor mediated protective effect on leaf growth, photosynthetic pigment and free radical scavenging activity. However, PTIO had little effect on maize leaves under UV-B stress compared with that of UV-B stress alone. $N^{\omega}$-nitro-L-arginine (LNNA), an inhibitor of nitric oxide synthase (NOS), significantly increased $H_2O_2$ and MDA accumulation and decreased antioxidant enzyme activities in maize leaves under UV-B stress. This demonstrates that NOS inhibitor LNNA has opposite effects on oxidative resistance. From these results it is suggested that NO might act as a signal in activating active oxygen scavenging system that protects plants from oxidative stress induced by UV-B radiation and thus confer UV-B tolerance.

• Journal of Korean Society on Water Environment
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• v.33 no.6
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• pp.736-743
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• 2017

In this study, 4-nonylphenol (4-NP), an endocrine disrupting chemical, was removed by ozone treatment processes under the various experimental conditions including UV irradiation, $TiO_2$ addition. The ozone flow rate and concentration were maintained at $1.0L{\cdot}min^{-1}$ and $70{\pm}5mg{\cdot}L^{-1}$. The pH, COD and TOC of the samples were obtained every 10 minutes for 60 minutes in laboratory scale batch reactor. We found that the combination of UV irradiation and $TiO_2$ addition for ozonation improves the removal efficiency of COD and TOC in 4-NP aqueous solution. In case of the $O_3/UV/TiO_2$ system, COD and TOC were greatly reduced to 85.3 ~ 94.0% and 89.2 ~ 97.2%, respectively. 4-NP degradation rate constants, $k_{COD}$ and $k_{TOC}$, were calculated based on the COD and TOC values. Significantly, $k_{COD}$ and $k_{TOC}$ were improved in the $O_3/UV/TiO_2$ treatment process compared with single $O_3$ process, because the oxidation and the mineralization of 4-NP were increased by generating of the hydroxyl radical. The $k_{COD}$ and $k_{TOC}$ were obtained to be $5.81{\times}10^{-4}{\sim}10.8{\times}10^{-4}sec^{-1}$ and $11.9{\times}10^{-4}{\sim}19.4{\times}10^{-4}sec^{-1}$ in the $O_3/UV/TiO_2$ process. Activation energy ($E_a$) of ozone oxidation reaction based on $k_{COD}$ and $k_{TOC}$ were increased in order of $O_3/UV/TiO_2$ < $O3/UV$ < $O_3/TiO_2$ < $O_3$ process. It was confirmed that the addition of $TiO_2$ and UV irradiation to the ozone oxidation reaction significantly reduced the $E_a$ value and the degradation of 4-NP.

• 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.

• Journal of Environmental Science International
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• v.11 no.6
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• pp.589-596
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• 2002

Photocatalytic degradation of chlorpyrifos and diazinon, which are extensively used as an organophosphorous pesticide in the agriculture field, has been investigated with UV-radiated TiO$_2$ in aqueous phase. Photodegradation rate was increased with increasing pH of the solution. The removal efficiencies of chlorpyrifos and diazinon were 100% after 200 min in pH 9. Photodegradation followed a pseudo-first-order reaction. The rate constants of chlorpyrifos and diazinon were 0.0160min$\^$-1/ and 0.0180min$\^$-1/, respectively. NO$_3$$\^$-/, PO$_4$$\^$3-/, SO$_4$$\^$2-/ and Cl$\^$-/ were found as end products on the photocatalytic degradation of chlorpyrifos and diazinon with TiO$_2$/UV.

• Journal of Soil and Groundwater Environment
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• v.15 no.2
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• pp.10-17
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• 2010

Advanced oxidation processes (AOPs) have advantages to reduce the processing time and mineralize contaminants dissolved in groundwater. Recently, remediation techniques for organic contamination in groundwater have been studied, and technology using $UV/H_2O_2$ is generally accepted as one of the most powerful and reliable alternative for the remediation of groundwater contamination. In this study, $UV/H_2O_2$ technology, which generates hydroxyl radical ($\cdot$ OH) as known for strong non-selective oxidant, was used to degrade chlorinated solvents (TCE and PCE), and it was expanded to apply continuous stirred tank reactor (CSTR) system (i.e. combinations of three CSTR). The tested parameters for CSTR system were retention time and groundwater/$H_2O_2$ injection volume ratio. To find optimum parameters for CSTR system, various retention time (6 min ~ 90 min) and groundwater/$H_2O_2$ injection volume ratio (5/1 ~ 119/1) were tested. Other conditions for CSTR were adapted from the batch test results, which concentration of $H_2O_2$ and UV dose were 29.4 mM (0.1%) and 4.3 kWh/L, respectively. Based on the experimental results, the optimum parameters for CSTR system were 20 min for retention time and 119/1 for groundwater/$H_2O_2$ injection volume ratio. Applying these optimum conditions, chlorinated solvents (TCE and PCE) were removed at 99.9% and 99.6%. Moreover, the effluent concentrations of TCE and PCE are 0.036 mg/L and 0.087 mg/L, respectively, which are satisfied the regulatory level (TCE 0.3 mg/L, PCE 0.1 mg/L). Consequently, the CSTR system using $UV/H_2O_2$ technology can achieve high removal efficiency in the event of treatment of groundwater contaminated by chlorinated solvents (TCE and PCE).

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.320-320
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• 1999

• Journal of Environmental Science International
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• v.11 no.7
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• pp.757-763
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• 2002

The objective of this study is to delineate removal efficiency of the Linear alkylbenzene sulfonates(LAS) in solution by $TiO_2$ photocatalytic oxidation as a function of the following different experimental conditions : initial concentration of LAS, $TiO_2$ concentration, UV wavelength and pH of the solution. It was increased with decreasing initial concentration of LAS and with decreasing pH of the solution. Removal efficiency increased with increasing $TiO_2$ concentration but was almost the same at $TiO_2$ concentration of 2 g/L and 3 g/L, i.e., for initial LAS concentration of 50 mg/L. It was removal efficiency was 85% at 150 min in the case of $TiO_2$ concentration of 0.5 g/L but 100% after 150 min in the case of $TiO_2$ concentration of 1 g/L, 100% after 110 min in the case of $TiO_2$ concentration of 2 g/L and 3 g/L. UV wavelength affection on the removal efficiency of LAS decreased in the order of 254, 312 and 365 nm as increasing wavelength. But the removal efficiency of LAS was nearly the same at UV wavelength of 254 nm and 312 nm.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.8
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• pp.534-541
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• 2014

This study investigated a method to determine an efficient operating condition for the $UV/H_2O_2$ process. The OH radical scavenging factor is the most important factor to predict the removal efficiency of the target compound and determine the operating condition of the $UV/H_2O_2$ process. To rapidly and simply measure the scavenging factor, Rhodamine B (RhB) was selected as a probe compound. Its reliability was verified by comparing it with a typical probe compound (para-chlorobenzoic acid, pCBA); the difference between RhB and pCBA was only 1.1%. In a prediction test for the removal of Ibuprofen, the RhB method also shows a high reliability with an error rate of about 5% between the experimental result and the model prediction using the measured scavenging factor. In the monitoring result, the scavenging factor in the influent water of the $UV/H_2O_2$ pilot plant was changed up to 200% for about 8 months, suggesting that the required UV dose could be increased about 1.7 times to achieve 90% caffeine removal. These results show the importance of the scavenging factor measurement in the $UV/H_2O_2$ process, and the operating condition could simply be determined from the scavenging factor, absorbance, and information pertaining to the target compound.

• Journal of Korean Society on Water Environment
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• v.32 no.1
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• pp.23-29
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• 2016

Ozonation was investigated for its ability to remove pyruvic acid in a laboratory-scale batch reactor under various experimental conditions, including UV irradiation, TiO₂ addition, and variations in temperature. An ozone flow rate of 1.0 L min^-1 and a concentration of 75±5 mg L^-1 were maintained throughout the experiment, and pH, COD, and TOC were measured at 10 min intervals during a 60 min reaction. Our results confirmed that the combination of UV irradiation and photocatalytic TiO₂ in the ozonation reaction improved the removal efficiency of both COD and TOC in aqueous solution at 20℃. Pseudo first-order rate constants and activation energies were quantified based on the COD and TOC measurements. We observed that the O₃/UV, O₃/UV/TiO₂ system increased mineralization and reduced the activation energy (E_a) necessary for pyruvic acid decomposition.