• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.984-991
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• 2008

This paper reports experimental results, demonstrating the feasibility of horseradish peroxidase(HRP) and H$_2$O$_2$ to reduce phenol transport in saturated porous media. A laboratory-scale packed column reactor(ID: 4.1 cm, sand-bed height 12 cm) column was utilized to simulate injection of HRP and H$_2$O$_2$ into an aquifer contaminated with phenol. Effluent concentrations of phenol and polymerization products were monitored before and after enzyme addition under various experimental conditions(enzyme dose: 0$\sim$2 AU/mL, [ionic strength]: 5$\sim$100 mM, pH: 5$\sim$9). The concentration of phenol in the column effluent was found to decrease by nearly 90% in the presence of HRP(2 AU/mL) and H$_2$O$_2$ in the continuous flow system at pH 7 and ionic strength 20 mM. The influent phenol was converted in the system to insoluble precipitate, which deposited in pore spaces. The remains were discharged as soluble oligomers. About 8% of total pore volume in column system was decreased by deposition of polymer produced.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.215-221
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• 2006

This research presents results from laboratory and pilot-scale experiments to remove high-nitrate in pickling wastewater using the sequencing batch reactor (SBR) as a biological method. During the experimental periods, the influent concentrations of NOx-N and $Ca^{+2}$ were analyzed to be 350-1,600 and 700-800 mg/L, respectively. In order to provide carbon source for denitrification, methanol has been added in proportion to the influent nitrate loading. The mean concentrations of MLSS and MLVSS, the fraction of volatile solids in sludge and the sludge volume index were measured to be 27 g/L, 5 g/L, 18.5% and 7.5, respectively. The solid retention time was kept in the range of 18 to 22 days, specific denitrification rate ($U_{dn}$) was $0.301g{NO_3}^--N/gVSS/day$. The oxidized nitrogen concentration of effluent ranged 2-34 mg/L with an average of 5.2 mg/L, the overall reduction in total nitrogen was more than 99.2%. In order to treat the pickling wastewater including the high concentration of nitrate and $Ca^{+2}$, the continuous flow process is not suitable because the specific gravity of the sludge is considerably increased by $Ca^{+2}$, thus the SBR process is shown to be very effective to treat the pickling wastewater.

• Applied Chemistry for Engineering
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• v.1 no.2
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• pp.240-248
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• 1990

The catalytic activity and selectivity of metal loaded H-mordenite for transalkylation of $C_9$ aromatics were studied in a continuous flow fixed bed reactor under high pressure. Nickel loaded H-mordenite(T-Ni) catalyst showed high activity and slow decay of activity. Molybdenum and nickel loaded H-mordenite(T-NiMo) catalyst also showed high activity and suppressed coking of hydrocarbons. The selectivity of xylene for T-Ni and T-NiMo catalysts decreased with temperature, but that for T catalyst(commercial grade) monotonically increased with temperature within the experimental range. The performance of T-Ni and T-NiMo catalysts was better than that of T catalyst in terms of initial activity and its decay. The addition of Mo improved slightly stability of T-Ni catalyst.

• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.77-81
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• 2005

Porous-composite electrodes have been developed using silica gel, which reduce carbon aerogel usage with high cost. Silica gel powder was added to the carbon aerogel to simplify the manufacturing procedure and to increase the wet-ability, the mechanical strength and the CDI efficiency. Porous composite electrodes composed of carbon aerogel and silica gel powder were prepared by paste rolling method. Carbon aerosol composite electrodes with $10\times10cm^2$ are placed face to face between spacers, and assembled the four-stage series cells for CDI process. Each stage is composed of 45 cells. Four-stage series cells (flow through cells) for CDI process are put in continuous-system reactor containing 1,000ml-NaCl solution bath of 1,000 ppm. The four-stage series cells with carbon aerogel electrodes are charged at 1.2V and are discharged at 0.001V, and then read the current. Conclusively, removal efficiencies of ions using the four-stage series cells composed of carbon aerogel composite electrodes show good removal efficiency of $99\%$ respectively.

• Applied Biological Chemistry
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• v.28 no.4
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• pp.233-238
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• 1985

Glucoamylases catalyze a stepwise hydrolysis of starch with the production of glucose. In order to make an efficient conversion of starch into glucose, glucoamylases prepared from Rhizopus spp. (Sigma Co.) were attached to a porous glass and immobilized by glutaraldehyde-induced crosslinking. The porous glass used in this study was $ZrO_2$ coated, $40{\sim}80$ mesh, 550 A pore diameter. Using the forgoing glass, we could couple as much as 50mg of protein per gram of carrier. Substrate for the glucoamylase was an enzyrne-modified thin-toiling 30% cornstarch solution used where greater solubility and low viscosity are desired. Immobilized glucoamylase had an optimum pH 7.0 to the alkaline side of soluble enzyme. Km values of immobilized and soluble enzyme were 1.04 mM and 1.25mM, respectively. The thermal stability of glucoamylase was increased by immobilization and the immobilized enzyme showed an optimum temperature at $40{\sim}60^{\circ}C$. The continuous conversion of cornstarch to glucose by use of immobilized glucoamylase resulted in the production of a more than 90 DE product.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.18-27
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• 2021

This study aims to develop an improved evaluation technology for assessing CANDU-6 safety. For this purpose, the multiple steam generator tube rupture (mSGTR) followed by an unmitigated station blackout (SBO) in a CANDU-6 plant was selected as a hypothetical event scenario and the analysis model to evaluate the plant responses was envisioned into the MARS-KS input model. The model includes logic models for controlling the pressure and inventory of the primary heat transport system (PHTS) decreasing due to the u-tubes' rupture, as well as the main features of PHTS with a simplified model for the horizontal fuel channels, the secondary heat transport system including the shell side of steam generators, feedwater and main steam line, and moderator system. A steady state condition was successfully achieved to confirm the stable convergence of the key parameters. Until the turbine trip, the fuel channels were adequately cooled by forced circulation of coolant and supply of main feedwater. However, due to the continuous reduction of PHTS pressure and inventory, the reactor and turbine were shut down and the thermal-hydraulic behaviors between intact and broken loops got asymmetric. Furthermore, as the conditions of low-flow coolant and high void fraction in the broken loop persisted, leading to degradation of decay heat removal, it was evaluated that the peak cladding temperature (PCT) exceeded the limit criteria for ensuring nuclear fuel integrity. This study is expected to provide the technical bases to the accident management strategy for transient conditions with multiple events.

• Applied Chemistry for Engineering
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• v.25 no.5
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• pp.503-509
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• 2014

The carbon/porous silica composite membrane was fabricated in a simple manner, which could be successfully for the simultaneous separation and production of chiral epoxides and 1,2-diols, based on their differences in hydrophilic/hydrophobic natures. The chiral Co(III)-$BF_3$ salen catalyst adopted in the membrane reactor system has given the very high enantioselectivity and recyclability in hydrolysis of terminal epoxides such as ECH, 1,2-EB, and SO. The optically pure epoxide and the chiral catalyst were collected in the organic phase after hydrolysis reaction. The hydrophilic water-soluble 1,2-diol product hydrolyzed by chiral salen diffused into the aqueous phase through the SBA-16 or NaY/SBA-16 silica composite layer during the reaction. The water acted simultaneously as a reactant and a solvent in the membrane system. One optical isomer was obtained with high purity and yield, and furthermore the catalysts could be recycled without observable loss in their activity in the continuous flow-type membrane reactor.

• Journal of Soil and Groundwater Environment
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• v.11 no.2
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• pp.68-76
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• 2006

Anaerobic reductive dechlorination of tetrachloroethylene (PCE) to ethylene was investigated by performing laboratory experiments using semi-continuous flow two-in-series soil columns. The columns were packed with soils obtained from TCE-contaminated site in Korea. Site ground water containing lactate (as electron donor and/or carbon source) and PCE was pumped into the soil columns. During the first operation with a period of 50 days, injected mass ratio of lactate and PCE was 620:1 and incomplete reductive dechlorination of PCE to cis-DCE was observed in the columns. However, complete dechlorination of PCE to ethylene was observed when the mass ratio increased to 5,050:1 in the second operation, suggesting that the electron donor might be limited during the first operation period. Dechlorination rate of PCE to cis-DCE was $0.62{\sim}1.94\;{\mu}mol$ PCE/L pore volume/d and $2.76\;{\mu}mol$ cis-DCE/ L pore volume/d for that for cis-DCE to ethylene, resulting that net dechlorination rate in the system was 1.43 umol PCE/L pore volume/d. During the degradation of cis-DCE to ethylene, the concentration of hydrogen in column groundwater was $22{\sim}29\;mM$ and $10{\sim}64\;mM$ for the degradation of PCE to cis-DCE. These positive results indicate that the TCE-contaminated groundwater investigated in this study could be remediated through in-situ biological anaerobic reductive dechlorination processes.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.571-578
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• 2017

Bubbles are generated by the boiling of the cooling water when an accident occurs in the reactor and then in order to measure the void fraction, the Optical Fiber Probe(OFP) and optical camera are used in thermal hydraulic safety research. However, such an optical method is not suitable for measuring the void fraction in a $17{\times}17$ array of fuel rods due to the geometrical limitations. This study was conducted as a preliminary study using x-ray system and various phantoms before applying to rod bundles. Through radiographic and tomographic experiments, the tube voltage of the x-ray generator was 130 kVp and the tube current was 1 mA. In addition, it is possible to measure the hole of 1mm in size visually through the bubble resolution phantom, and it is confirmed that the contrast is relatively decreased in the inside of the freon in the case of the contrast evaluation using the road phantom. However, we could obtain good image without distortion when reconstructing the image. Bubble generation phantom experiments were used to confirm the flow direction of the bubbles and to acquire tomography images. The image J tool was used to measure the void fraction of 18 % for a single tomography image. This study has carried out previous researches for the measurement of the bubble rate around the nuclear fuel and could be used as a basic research for continuous research.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.206-214
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• 2005

Heterogeneously-catalyzed oxidation of aqueous phase trichloroethylene (TCE) over supported metal oxides has been conducted to establish an approach to eliminate ppm levels of organic compounds in water. A continuous flow reactor system was designed to effect predominant reaction parameters in determining catalytic activity of the catalysts for wet TCE decomposition as a model reaction. 5 wt.% $CoO_x/TiO_2$ catalyst exhibited a transient period in activity vs. on-stream time behavior, suggesting that the surface structure of the $CoO_x$ might be altered with on-stream hours; regardless, it is probable to be the most promising catalyst. Not only could the bare support be inactive for the wet decomposition reaction at $36^{\circ}C$, but no TCE removal also occurred by the process of adsorption on $TiO_2$ surface. The catalytic activity was independent of all particle sizes used, thereby representing no mass transfer limitation in intraparticle diffusion. Very low TCE conversion appeared for $TiO_2$-supported $NiO_x$ and $CrO_x$ catalysts. Wet oxidation performance of supported Cu and Fe catalysts, obtained through an incipient wetness and ion exchange technique, was dependent primarily on the kinds of the metal oxides, in addition to the acidic solid supports and the preparation routes. 5 wt.% $FeO_x/TiO_2$ catalyst gave no activity in the oxidation reaction at $36^{\circ}C$, while 1.2 wt.% Fe-MFI was active for the wet decomposition depending on time on-stream. The noticeable difference in activity of the both catalysts suggests that the Fe oxidation states involved to catalytic redox cycle during the course of reaction play a significant role in catalyzing the wet decomposition as well as in maintaining the time on-stream activity. Based on the results of different $CoO_x$ loadings and reaction temperatures for the decomposition reaction at $36^{\circ}C$ with $CoO_x/TiO_2$, the catalyst possessed an optimal $CoO_x$ amount at which higher reaction temperatures facilitated the catalytic TCE conversion. Small amounts of the active ingredient could be dissolved by acidic leaching but such a process gave no appreciable activity loss of the $CoO_x$ catalyst.