• Resources Recycling
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• v.21 no.6
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• pp.65-73
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• 2012

Selective catalytic reduction(SCR) catalysts are obtained from de-NOx system of thermoelectric power plant. A process was developed for valuable metals such as vanadium and tungsten recovery from spent SCR catalyst by using soda roasting followed by water leaching. Spent SCR catalyst having $V_2O_5$(1.23 mass %) and $WO_3$(7.73 mass %). For getting soluble metal forms of the targeted metals like vanadium and tungsten soda roasting process was implemented. In soda roasting process, sodium carbonate added 5 equivalent ratio at roasted temperature $850^{\circ}C$ with 120 min roasted time for $544{\mu}m$ particle size of spent SCR catalyst. After soda roasting process moved to water leaching for roasted spent catalyst. Before leaching process the roasted spent catalyst was grinded up to $-45{\mu}m$ size. The leaching time is 30 min at $40^{\circ}C$ temperature, 10 % pulp density. The final leaching efficiency obtained 46 % of vanadium and 92 % of tungsten from present process.

• Resources Recycling
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• v.18 no.6
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• pp.30-37
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• 2009

Silica sol was prepared from the mixture of sodium silicate solution and oxidized silicate solution in which sodium had been removed by sol-gel process. The properties of sodium silicate solution and silicate solution thus prepared were characterized by yellow silicomolydate method. Moreover, the formation and growth of silica sol from sodium silicate solution was investigated. Sodium silicate solution with 2% of $SiO_2$ contains 95% of reactive silicate, and 50% of reactive silicate participates sol-gel reaction. From the results of FT-IR analysis, it was found that the intensity of silanol bond decreased and the intensity of siloxane bond increased with increasing reaction temperature. Zeta potential of silica sol prepared at each condition was -40~-60 mV and it could be known that silica sol in this study was well dispersed. The silica sol with 5~10 nm size could be prepared by heating the mixed solution of sodium silicate and silicate solution. And the silica sol grew into about 20 nm as silicate solution was added to silica sol solution.

• Resources Recycling
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• v.29 no.3
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• pp.36-42
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• 2020

In the present study, gravity separation of speiss (6.74 g/㎤) and limestone (2.7 g/㎤) was investigated using a vibrating 1 mm-zirconia ball (5.6 g/㎤) bed as a medium. The floating ratio and separation efficiency with increasing the number of spiess and limestone granules were examined by changing the vibration frequency from 18 Hz to 26 Hz. During the vibration, the zirconia balls circulate inside the vessel, and the spiess granules sink with the zirconia balls, but limestone granules remain on the surface of the zirconia ball bed. As the number of particles of spiess and limestone granules increased, it was observed that the granules were congested in the path of the granule sinking, so the rate of particle sinking decreased, and that limestone granules overlapping with the spiess granule also sunk. Therefore, the separation efficiency decreases with increasing the number of granules, but when the vibrational frequency increases, there is no more congestion and the separation efficiency increases. When each of the three particles was added, a separation efficiency of 100% was acheived at 22 Hz, which indicates that a dry gravity separation process that does not require a drying process is possible.

• Applied Microscopy
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• v.30 no.1
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• pp.101-111
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• 2000

In this study, the distribution of lectin receptors in Paragonimus westermani tissue was explored using colloidal gold label complexed with lectin WGA purified from wheat germ (Triticum vulgare). The lectin WGA gold complex, shown to recognize GlcNAc (N-acetylgalactosamine) and NeuNAc (N-acetylneuraminic acid) regions, was applied to detect binding sites in Lowicryl HM 20 sections viewed under electron microscope. Labeled sections of the metacercaria revealed gold particles specifically distributed on the tegumental syncytium and lamella of the excretory canal. Labeling of young adult tissue was then quantified and compared to that of adult worm tissue. Adult worm tissue sections resulted in specific gold particle distribution on the lamella of caecal epithelium and excretory canal. These results indicate that lectin WGA receptors are located in the tegumental syncytium and lamella of the excretory canal of the metacercariae, and in the lamella of the caecum and excretory canal of the young adult and adult. Therefore, the GlcNAc and NeuNAc regions in the tegumental syncytium appear to be functionally associated with cell-recognition and protection from the immune system of the host, and linked with membrane transport and absorption of nutrients in the lamella of the excretaory canal and caecal epithelia.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.310-315
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• 2019

This study conducted a series of studies to find alternative ways to use Chlorine Bypass System-dust(CBS-dust) in cement production. The results of engineering characteristics of CBS-dust are summarized as follows. First of all, the density of CBS-dust is 2.40, lighter than cement and the pH was 12.50 which was strong alkaline. In terms of particle size, it was 11.70 ㎛ which was finer than cement. With chemical properties, calcium oxide(CaO) was the highest as 35.10%, potassium oxide(K₂O) was 32.43%, potassium chloride(KCl) was 19.46%, sulfur oxide(SO₃) was 6.81%, and the remaining chemical components are SiO₂, Fe₂O₃, Al₂O₃, MgO, and the like. Therefore, if CBS-dust is used as early-strength chemical admixtures in the concrete secondary products that use a large amount of mineral admixtures without rebar, it can be an effective method for increasing the strength of concrete as an alkali activator and preventing early-frost damage of Cold Weather Concrete.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.145-152
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• 2008

A fault gouge zone which is about 25cm thick crops out along a small valley in Yangbuk-myeon, Gyeongju city. It is divided into greenish brown gouge and bluish gray gouge by color. Under the microscope, the gouges have a lot of porphyroclasts composed of old gouge fragments, quartz, feldspar and iron minerals. Clay minerals are abundant in matrix, defining strikingly P foliation by preferred orientation. Microstructural differences between bluish pay gouge and greenish brown gouge are as follows: greenish brown gouge compared to bluish gray gouge is (1) rich in clay minerals, (2) small in size and number of porphyroclasts, and (3) plentiful in iron minerals which are mostly hematites, while chiefly pyrites in bluish gray gouge. Hematites are considered to be altered from pyrites in the early-formed greenish brown gouge under the influence of hydrothermal fluids accompanied during the formation of bluish gray gouge that also precipitated pyrites. It is believed that the fault core including bluish gray gouge zone and greenish brown gouge zone was formed by progressive cataclastic flow. In the first stage the fault core initiates from damage zone of early faulting. In the second stage damage zone actively transforms into breccia zone by repeated fracturing. The third stage includes greenish brown (old) gouge formation in the center of the fault core mainly by particle grinding. In the third stage further deformation leads to the formation of new (bluish gray) gouge zone while old gouge zone undergoes strain hardening. Consequently, the whole gouge zone in the core widens.

• Ecology and Resilient Infrastructure
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• v.2 no.2
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• pp.167-176
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• 2015

The water quality of the Gulpo Stream flowing through Incheon, Bucheon, Seoul, and Kimpo is getting worse due to a slow flow rate and bank constructions by stream channelization as well as an inflow of pollutants from living-sewages and factory-sewages. Besides, a dry stream phenomenon caused by a lack of maintenance water upstream makes a self-purification system worse, and the water quality of the Gulpo Stream is currently at its lowest level. The accumulated sludge of the streambed is mostly formed by the deposition of particle pollutants due to the slow flow rate and an artificially straightened stream channel. This accumulated sludge adsorbs a great quantity of organic materials and heavy metals. Because of the internal contamination possibility by a re-gushing, even after the pollution source is removed, it can cause future water pollution. Without a total examination as previously recommended, it is considered difficult to accomplish practical efficiency. In conclusion, the management of periodic sediment management such as dredging would be necessary in the Gulpo Stream because sediment could be an internal pollution source of stream water under anaerobic conditions.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.316-327
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• 1997

Polycrystalline $Sr_{2}Nb_{2}O_{7}$ and $La_{2}Ti_{2}O_{7}$ ceramics with very high Curie temperatures were synthesized by the chemical coprecipitation method (CCP). The powders synthesized were identified by XRD and their sintering behavior and physical properties were studied. The grain-orientation and electrical properties of sintered ceramics were investigated as a function of firing temperature. Single phase could be obtained by CCP method at temperature lower than that of the conventional method by 100 - $150^{\circ}C$. Strontium niobate, $Sr_{2}Nb_{2}O_{7}$, powder was Prepared by CCP method at temperatures as low as $800^{\circ}C$ via intermediate phase of $Sr_{5}Nb_{4}O_{15}$ formed at $700^{\circ}C$. The resulting CCP-derived powder was observed to have finer and more uniform particle size distribution than those obtained through the conventional or the molten salt synthesis method. Sintering of CCP-derived $Sr_{2}Nb_{2}O_{7}$ powder at $1500^{\circ}C$ yielded a highly dense ceramics with 97% theoretical density. Very high grain-orientation developed along the (0k0) direction was observed by SEM, which resulted in anisotropic dielectric properties of the sintered samples, with the dielectric constant values approaching those for single crystal.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1141-1147
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• 2006

In order to applicate a newly method for powdered activated carbon(PAC) selection based on economic efficiency, PAC adsorption tests were performed for removal of MIB and dissolved organic carbon(DOC) in drinking water supplies. The removal rate of MIB increased when the PAC dose increased. The Coal-based PACs were superior for adsorption of MIB compared to wood-based PACs. PAC adsorption of DOC and $UV_{254}$ were a little different for different PACs and types of raw water, but both were lower than adsorption of MIB. Among the tested PACs, the one called P-1000 was most effective for removal of MIB, DOC and $UV_{254}$. Most of the organics in the tested samples were proven by excitation emission matrix(EEM) results to be fulvic-like materials. Especially, fulvic-like materials, humic-like materials, and soluble microbial byproduct(SMP)-like materials decreased after contact with PAC. P-1000 which had the lowest MIB cost index(MCI) was selected as the optimum PAC for the target water. PAC efficiency and treatability, particle size and distribution, and the cost associated with PAC dosing for MIB removal according to DOC concentration should all be considered before making the final selection of the best PAC for the target water.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.936-941
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• 2010

This study was conducted to investigate formaldehyde removals by silver nano-particles attached on the surface of granular activated carbon (Ag-AC) and to compare the results to those obtained with ordinary activated carbon (AC). The BET analysis showed that the overall surface area and the fraction of micropores (less than $20{\AA}$ diameter) of the Ag-AC were significantly decreased because the silver particles blocked the small pores on the surface of the Ag-AC. The formaldehyde removal capacity of the Ag-AC determined using the Freundlich isotherm was higher than that of AC. Despite the decreased BET surface area and micropore volume, the Ag-AC had the increased removal capacity for formaldehyde, presumably due to catalytic oxidation by silver nano-particles. In contrast, the adsorption intensity of the Ag-AC, estimated by 1/n in the Freundlich isotherm equation, was similar to that of the ordinary AC, indicating that the surface modification using silver nano-particles did not affect the adsorption characteristics of AC. In a column experiment, the Ag-AC also showed a longer breakthrough time than that of the AC. Simulation results using the homogeneous surface diffusion model (HSDM) were well fitted to the breakthrough curve of formaldehyde for the ordinary AC, but the predictions showed substantial deviations from the experimental data for the Ag-AC. The discrepancy was due to the catalytic oxidation of silver nano-particles that was not incorporated in the HSDM. Consequently, a new numerical model that takes the catalytic oxidation into accounts needs to be developed to predict the combined oxidation and adsorption process more accurately.