• 한국환경과학회지
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• 제17권6호
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• pp.581-589
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• 2008

This study was carried out to evaluate the effect of water quality of cooling tower on Legionella pneumophila disinfection using Ru/Ti electrode. The influences of parameters such as pH, turbidity, $CaCO_3$ and TOC were investigated using laboratory scale batch reactor. Oxidants such as free Cl, $ClO_2,\;H_2O_2\;and\;O_3$ were measured. The results showed that all of the water quality parameters of cooling tower had deteriorated disinfection of Legionella pneumophila. When the turbidity, $CaCO_3$ and TOC was increased, oxidants which was generated during electrolysis was decreased. pH, free Cl, $ClO_2\;and\;H_2O_2$ concentration were decreased with the increase of pH, whereas $O_3$ concentration was increased with the increase of pH. The order of effect of water quality on the disinfection performance for Legionella pneumophila was turbidity > $CaCO_3$ > TOC > pH. To obtain the safety standard (1000 CFU/L), the simultaneous increase current and NaCl dosage was needed.

• 상하수도학회지
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• 제11권4호
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• pp.133-141
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• 1997

In order to treat the landfill leachate, $UV/TiO_2/H_2O_2$ system connected with biological treatment was investigated, and proper pretreatment methods were examined to reduce the load on the system considering economical and technical efficiency. It was more profitable to put $H_2O_2$ into the system in the early stage for the sample which was treated with $H_2SO_4$ to decrease alkalinity and with $FeCl_3-6H_2O$ flocculation. Because the required reaction time run up by increasing $H_2O_2$ input amount, though the COD was reduced slightly, the optimal $H_2O_2$ input amount should be determined for the desired COD and the economical efficiency. The appropriate way to get the lowest COD in the shortest time was the method to treat the sample which was controlled to pH 3.5 after adjusting to pH 12 and put 500 ppm $H_2O_2$ into the system. In that case, to increase $H_2O_2$ input amount was not profitable for the system efficiency. The sufficient photocatalytic excited time was required to reduce the photocatalytic decomposition time for the sample which was gone through the alkali state.

• 상하수도학회지
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• 제24권1호
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• pp.109-117
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• 2010

In the present study, the degradation characteristics of Lindane by Advanced Oxidation Processes(UV/$H_2O_2$, Photo-Fenton process) were studied. The degradation efficiency of Lindane in aqueous solution was investigated at various initial pH values, Fenton's reagent concentrations and initial concentrations of Lindane. GC-ECD was used to analyze lindane. Lindane has not been degraded without application of AOPs over two hours. But, approximately 5% of lindane was degraded with UV or $H_2O_2$ alone. Lindane with UV/$H_2O_2$ process showed approximately 7% higher removal efficiency than $H_2O_2$ process. In the UV/$H_2O_2$ process, the pH values did not affect the removal efficiency. The optimal mole ratio of $H_2O_2/Fe^{2+}$ for lindane degradation is about 1.0 in Photo-Fenton process. Also, the experimental results showed that lindane removal efficiency increased with the decrease of initial concentration of lindane. Under the same conditions, the order lindane of removal efficiency is as following : Photo-Fenton process > UV/$H_2O_2$ process > $H_2O_2$ process. In addition, intermediate products were identified by GC-MS techniques. Than PCCH(Pentachlorocyclohexene) was identified as a reaction intermediate of the Photo-Fenton process.

• 한국환경과학회지
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• 제16권12호
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• pp.1425-1430
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• 2007

This study was conducted to investigate the effect of ozonated water and ozonated water+hydrogen peroxide treatment of residual procymidone in perilla leaf containing 20 mg/L procymidone. Samples was treated with ozonated water containing 1.0, 2.0 and 3.0 mg $O_3/L$ ozone and hydrogen peroxide water containing 1.0, 2.0 and 3.0 mg $H_2O_2/L$ hydrogen peroxide in pH 5, 7 and 9, respectively, at $15^{\circ}C$. Procymidone removal rate was 26.5% in 7 days at $15^{\circ}C$ and optimum condition of procymidone removal was the case of treating with ozonated water containing 2.0 mg $O_3/L$ and pH 9. As the result procymidone removal rate was about 96.5%. In this case of adding hydrogen peroxide, optimum condition of procymidone removal was $1:0.5{\sim}1(O_3:H_2O_2)$. However, procymidone was nearly removed with the treatment of hydrogen peroxide water only.

• 대한화학회지
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• 제67권5호
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• pp.333-338
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• 2023

In this study, the H₂O reaction with SiO clusters was investigated using ab initio Monte Carlo simulations and density functional theory calculations. Three chemistry models, PBE1/DGDZVP (Model 1), PBE1/DGDZVP (Si atom), and aug-cc-pVDZ (O and H atoms), (Model 2) and PBE1/aug-cc-pVDZ (Model 3), were used. The average bond lengths, as well as the relative and reaction energies, were calculated using Models 1, 2, and 3. The average bond lengths of Si-O and O-H are 1.67-1.75 Å and 0.96-0.97 Å, respectively, using Models 1, 2, and 3. The most stable structures were formed by the H transfer from an H₂O molecule except for Si₃O₃-H₂O-1 cluster. The Si₃O₃ cluster with H₂O exhibited the lowest reaction energy. In addition, the Bader charge distributions of the Si_nO_n and (SiO)_n-H₂O clusters with n = 1-7 were calculated using Model 1. We determined that the reaction sites between H₂O and the SiO clusters possessed the highest fraction of electrons.

• Corrosion Science and Technology
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• 제21권6호
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• pp.466-475
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• 2022

Surface oxides and intergranular (IG) oxidation phenomena in Alloy 600 depending on hydrogen concentration were characterized to obtain clear insight into the primary water stress corrosion cracking (PWSCC) behavior upon exposure to pressurized water reactor primary water. When hydrogen concentration was between 5 and 30 cm³ H₂/kg H₂O, NiFe₂O₄ and NiO type oxides were found on the surface. NiO type oxides were found inside the oxidized grain boundary when hydrogen concentration was 5 cm³ H₂/kg H₂O. However, only NiFe₂O₄ spinel on the surface and Ni enrichment were observed when hydrogen concentration was 30 cm³ H₂/kg H₂O. These results indicate that the oxidation/reduction reaction of Ni in Alloy 600 depending on hydrogen concentration can considerably affect surface oxidation behavior. It appears that the formation of NiO type oxides in a Ni oxidation state and Ni enrichment in a Ni reduction (or metallic) state are common in primary water. It is believed that the above different oxidation/reduction reactions of Ni in Alloy 600 depending on hydrogen concentration can also significantly affect the resistance to PWSCC of Alloy 600.

• 상하수도학회지
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• 제10권4호
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• pp.64-72
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• 1996

The effect of $O_3$, $O_3/pH$, and $O_3/H_2O_2$, $O_3/UV$, and $H_2O_2/UV$ advanced oxidation process(AOP) were investigated for the treatment of tetrachloroethylen(PCE) at various condition. The removal efficiency of 10, 20, and 30ppm PCE by ozonation were almost same, only about 60%. And pseudo first-order rate constants, ko for overall oxidation was about 0.097($min^{-1}$). In the $O_3/pH$ AOP experiment for the 20ppm PCE, the removal rate of PCE increased with the increase of pH. However, mineralization rate of PCE at pH 7 was higher than at pH 10. In the $O_3/H_2O_2$ AOP, the removal rate of PCE was the highest at peroxide-to-ozone dosage ratio of about 0.9, which PCE was removed over 99.95%. Despite 42% of PCE was directly photolyzed by the UV irradiation, the removal efficiency of PCE by $O_3/UV$ AOP was only about 70%. In $H_2O_2/UV$ AOP, the removal efficiency of PCE increased to about 98% in proportion to the $H_2O_2$ injection concentration at constant UV intensity of 5W/l.

• 상하수도학회지
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• 제23권5호
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• pp.669-678
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• 2009

The reduction of excess activated sludge from petrochemical plant was investigated by the electro fenton (E-Fenton) process using electrogenerated hydroxyl radicals which lead to mineralization of activated sludge to $CO_2$, water and inorganic ions. Factors affecting the disintegration efficiency of excess activated sludge in E-Fenton process were examined in terms of five criteria: pH, $H_2O_2/Fe^{2+}$ molar ratio, current density, initial MLSS (mixed liquid suspended solids) concentration, $H_2O_2$ feeding mode. TSS total suspended solid and $TCOD_{cr}$ reduction rate increased with the increasing $H_2O_2/Fe^{2+}$ molar ratio and current density until 42 and $6.7 mA/cm^2$, respectively but further increase of $H_2O_2/Fe^{2+}$ molar ratio and current density would reduce the reduction rate. On the other hand, as expected, increasing pH and initial MLSS concentration of activated sludge decreas TSS and $TCOD_{cr}$ reduction rate. The E-Fenton process was gradually increased during first 30 minutes and then linearly proceed till 120 minutes. The optimal E-Fenton condition showed TSS reduction rate of 62~63% and $TCOD_{cr}$ (total chemical oxygen demand) reduction rate of 55~56%. Molar ratio $H_2O_2/Fe^{2+} = 42$ was determined as optimal E-Fenton condition with initial $Fe^{2+}$ dose of 5.4 mM and current density of $6.7{\sim}13.3 mA/cm^2$, initial MLSS of 7,600 mg/L and pH 2 were chosen as the most efficient E-Fenton condition.

• 대한화학회지
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• 제24권6호
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• pp.444-451
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• 1980

극성용매에서 전자의 용매화과정을 구체적으로 고찰하여 보기 위하여 테트라히드로퓨란(THF)-물 이성분계의 메디움효과를 측정하였다. 이 메디움효과는 Pt|$H_2Q$, Q, HCI, THF, $H_2O$|KC1 | $Hg_2Cl_2$|Hg(Pt) 셀로 수용액과 다른 용액(TGF-$H_2O$)에서 결정된 $H^+$ 이온에 대한 자유에너지 변화의 차(${\Delta}{\Delta}G_0$)를 이용하여 연구하였다. 여기서 $H_2Q$와 Q는 히드로퀴논과 퀴논을 각각 나타낸다. 자유에너지 변화의 차와 용매화된 전자의 최대흡수 에너지에 대한 용매의 유전상수 영향을 고찰하기 위하여 THF에서 $H_2O$의 회합정도를 관찰하였다. $H_2O$의 회합정도는 $H_2O$의 근적외선 스펙트럼을 이용하여 분석하였다. 이들 실험결과로부터 이성분 혼합용매에서 전자나 다른 이온의 용매화는 용매의 특정성분과 선택적으로 진행된다는 것을 알았다.

• 천문학회보
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• 제40권2호
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• pp.42.2-43
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• 2015

Massive stars play a major role in the interstellar energy budget and the shaping of the galactic environment. The water molecule is thought to be a sensitive tracer of physical conditions and dynamics in star-forming regions because of its large abundance variations between hot and cold regions. Herschel/HIFI allows us to observe the multiple rotational transitions of H2O including the ground-state levels, and its isotopologues toward high-mass star-forming regions in different evolutionary stages. Photodissociation regions (PDRs) are also targeted to investigate the distribution of water and its chemistry. We present line profiles and maps of H2O using data from two guaranteed-time key programs "Water In Star-forming regions with Herschel" and "Herschel observations of EXtra-Ordinary Sources". We analyze the temperature and density structures using LTE and non-LTE methods. We also estimate turbulent and expansion velocities, and abundance of water in the inner and outer envelopes using the 1D radiative transfer code. Around high-mass protostars we find H2O abundances of ~10-8-10-9 for the outer envelope and ~10-4-10-5 for the inner envelope, and expansion and turbulent velocities range from 1.0 km s-1 to 2.0 km s-1. The abundances and kinematic parameters of the sources do not show clear trends with evolutionary indicators. The Herschel/HIFI mapping observations of H2O toward the Orion Bar PDR show that H2O emission peaks between the shielded dense gas and the radicals position, in agreement with the theoretical and the observational PDR structure. The derived H2O abundance is ~10-7 and peaks at the depth of AV ~8 mag from the ionization front. Together with the low ortho-to-para ratio of H2O (~1) presented by Choi et al. (2014), our results show that the chemistry of water in the Orion Bar is dominated by photodesorption and photodissociation.