• Environmental Analysis Health and Toxicology
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• 제19권3호
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• pp.271-278
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• 2004

Epoxy resins are mostly used as a molding material for drinking water tank. Bisphenol A is used at a constituent material for epoxy resins and is widely suspected to act as an endocrine disrupter. In this study, we investigated embryo hatching in zebrafish reared in water undergone leaching process of expoxy resin, and found a decreased survival rate. Bisphenol A eluted from epoxy resin in drinking water tank was completely degraded by TiO$_2$ photocatalysis. We detected 7.8 ng/ml of bisphenol A in epoxy resin tank, and observed that the concentration was undetectable after 48h photocatalysis over TiO$_2$. There was no toxicity in hatching rates in zebrafish and morphogenesis after photocatalysis. The effect of TiO$_2$ photocatalytic reactions on the catalase activities in the f]y stage of zebrafish was also examined. At 1 week post hatching, cataiase activities were higher both in the group of epoxy resin with 48 h TiO$_2$ photocatalysis and in the TiO$_2$ photocatalysis for 48 hours were higher than control group. However catalase activities of the treatment group of epoxy resin by TiO$_2$ photocatalysis for 48 hours were similar to control in 5 weeks post hatching fries. In conclusion, the toxicity of TiO$_2$ photocatalysis was not observed in this zebrafish.

• 한국분말재료학회지
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• 제24권4호
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• pp.315-320
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• 2017

There has been much interest in recycling electronic wastes in order to mitigate environmental problems and to recover the large amount of constituent metals. Silver recovery from electronic waste is extensively studied because of environmental and economic benefits and the use of silver in fabricating nanodevices. Hydrometallurgical processing is often used for silver recovery because it has the advantages of low cost and ease of control. Research on synthesis recovered silver into nanoparticles is needed for application to transistors and solar cells. In this study, silver is selectively recovered from the by-product of electrodes. Silver precursors are prepared using the dissolution characteristics of the leaching solution. In the liquid reduction process, silver nanoparticles are synthesized under various surfactant conditions and then analyzed. The purity of the recovered silver is 99.24%, and the average particle size of the silver nanoparticles is 68 nm.

• 한국환경농학회지
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• 제12권3호
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• pp.281-297
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• 1993

Nitrogen is an element required to meet optimal plant growth. However, when it was applied (as chemical fertilizer or animal waste) more than the demand of plant and managed it unreasonably can be accumulated in subsoil and leached from soil system. Nitrogen also can be act as an pollutant to soil and water through water contamination if its concentration exceed the critical level. The concentration and downward movement of nitrate in soil is influenced by cultural practices and soil properties. High level of nitrate nitrogen in drinking water is harzadrous for animal and human health, especially for infants and the restoration of the quality of groundwater is impossible by now. Therefore it is the only way to prevent from leaching of nitrate nitrogen to keep the quality of groundwater as vital water resource. The aims of the presentation of this review paper are to understand the relationship between agricultural practices and the concentration of nitrate nitrogen in groundwater and to suggest further informations for the rational management methods to reduce the leaching of nitrate nitrogen in soil.

• 한국재료학회지
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• 제9권6호
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• pp.615-621
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• 1999

The new process in order to fabricate of Ni catalyst with high activity by the mechanochemical(MC) method which was combined the mechanical alloying(MA) and the chemical treatment process. The microstructure and characterization of mechanically alloyed Ni-5-wt% Al powder and Ni catalyst gained by alkali leaching were investigated byt he various analysis such as XRD, SEM-EDS, HRTEM and laser particle analyzer. The steady state powder with 1~2$\mu\textrm{m}$ mean particle size was obtained after 30hr milling with the PCA of 2 wt% stearic acid under the condition of grinding stainless steel ball to powder ratio of 60:1 and rotating speed fo 300rpm. According to result of HRTEM diffraction pattern, MA powder of the steady state was nanocrystalline $Al_3$$Ni_2$ intermetallic compound. Ni catalyst was obtained after KOH leaching of the steady state powder was about 20nm nanocrystalline which contained about 8 wt % Al.

• 아시안잔디학회지
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• 제7권2_3호
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• pp.55-60
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• 1993

Soil profile was well developed into four horizons, $A_1$, $A_3$, $B_2$and C at 100cm-depth in most four golf courses in Kyonggi province. Distribution of root system of Korean lawngrass was abundant in dark yellowish or yellowish brown $A_1$ horizon with low hardness(8~14mm yamanaka scale), moderately in yellowish brown $A_3$ horizon with moderate hardness(16~23mm) rarely in $B_3$horizon(15~60cm depth) and no in C horizon. Optimum soil hardness for good root growth of Korean lawngrass appeared to be less than 16mm mineral nutrient contents. Such as Ca++, Mg++, K+, Mn++ and Fe showed relatively higher concentration in lower horizon indicating the leaching of minerals. The increasing tendency of soil pH with depth seemed to the result of mineral leaching. There was significant positive correlation between Ca+Mg and pH, manganese content appeared to be too high(261~789ppm) in $A_1$ horizon. The contents of organic matter and phosphorus were bight in $A_1$ horizon and greatly varied among golf courses.

• 방사성폐기물학회지
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• 제19권3호
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• pp.323-330
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• 2021

Silver tellurite glasses with melting temperature of approximately 700℃ were developed to immobilize ¹²⁹I wastes. Long-term dissolution tests in 0.1 M acetic acid and disposability assessment were conducted to evaluate sustainability of the glasses. Leaching rate of Te, Bi and I from the glasses decreased for up to 16 d, then remained stable afterwards. On the contrary, tens to tens of thousands of times more of Ag was leached in comparison to the other elements; additionally, Ag leached continuously for all 128 d of the test owing to the exchange of Ag⁺ and H⁺ ions between the glasses and solution. The I leached much lower than those of other elements even though it leached ~10 times more in 0.1 M acetic acid than in deionized water. Some TeO₄ units in the glass network were transformed to TeO₃ by ion exchange and hydrolysis. These silver tellurite glasses met all waste acceptance criteria for disposal in Korea.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1357-1371
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• 2024

To investigate the influence of different burial conditions on the seepage characteristics of loose sandstone in the leaching mining of sandstone uranium ore, this study applied different ground pressures and water pressures to rock samples at different burial depths to alter the rock's seepage characteristics. The permeability, pore distribution, and particle distribution characteristic parameters were determined, and the results showed that at the same burial depth, ground pressure had a greater effect on the reduction in permeability than water pressure. The patterns and mechanisms are as follows: under the influence of ground pressure, increasing the burial depth compresses the pores in the rock samples, decreases the proportion of effective permeable pores, and causes particle fragmentation, which blocks pore channels, resulting in a decrease in permeability. Under the influence of water pressure, increasing the burial depth expands the pores but also causes hard clay particles to decompose and block pore channels. As the burial depth increases, the particles eventually decompose completely, and the permeability initially decreases and then increases. In this experiment, the relationships between permeability and the proportion of pores larger than 0.15 ㎛ and the proportion of particles smaller than 59 ㎛ were found to be the most significant.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.186-198
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• 2022

Heavy metals recovery from Printed Circuit Boards industrial wastewater is crucial because of its cost effectiveness and environmental friendliness. In this study, a copper recovery route combining the sequential processes of acid leaching and LIX 984N extracting with an electrowinning technique from Printed Circuit Boards production's sludge was performed. The used residual sludge was originated from Hanoi Urban Environment One Member Limited Company (URENCO). The extracted solution from the printed circuit boards waste sludge containing a high copper concentration of 19.2 g/L and a small amount of iron (0.575 ppm) was used as electrolyte for the subsequent electrolysis process. By using a simulation model for multi-step current electrolysis, the reasonable current densities for an electrolysis time interval of 30 minutes were determined, to optimize the specific consumption energy for the copper recovery. The mathematical simulation model was built to calculate the important parameters of this process.

• 대한화학회지
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• 제30권5호
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• pp.488-492
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• 1986

경북 원성군 감포 78에서 산출되는 벤토나이 중 몬모리노나이트를 분리하여 Ca, Mg-형을 NaCl용액으로 처리하여 Na-형 몬모리노나이트를 만들었다. 이때 가장 적당한 조건은 0.05M NaCl용액으로 80${\circ}C$에서 24시간 반응시켜 치환되는 $Ca^{2+}$, $Mg^{2+}$량을 EDTA로 적정하여 양이온 교환 용량을 구하였다. Na-형에 $Ln^{3+}$이온용액과 같은 조건하에서 반응시켜 $Ln^{3+}$-형 몬모리노나이트를 만들었다. 치환되는 량은 $Ln^{3+}$이온들의 이온 크기에는 무관함을 알 수 있었고, X-선 회절 실험결과 순수한 몬모리노나이트를 얻을 수 있음을 밝혔고, 또한 $Ln^{3+}$형은 새로운 결정모양이 되는 것을 알 수 있었다. 이는 단순한 틈새끼우기 반응이 아니 새로운 결정형이 생성됨을 알 수 있다.

• 한국환경농학회지
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• 제28권4호
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• pp.340-346
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• 2009

Chromated copper arsenate (CCA) is a chemical wood preservative that has been intensively used to protect wood from decay during the last few decades. CCA is widely used to build structures such as decks, fences, playgrounds and boardwalks. However, structures constructed of CCA-treated wood have caused adverse environmental effects due to leaching of Cr, Cu and As into surrounding soils. This research was conducted to monitor the vertical and horizontal distribution of Cr, Cu and As in soils adjacent to CCA-treated wood structures in Korea. Two structures constructed with CCA-treated wood were selected at Hongcheon and Chuncheon in Gangwon Province, South Korea. Eleven soil profile samples were collected at depths of 0 to 80 cm at each site, while 12 surface soil samples were collected at distances of 0 to 200 cm from each structure. The soil chemical properties, soil particle size distribution and total metal concentrations were then determined. The results revealed that soils near CCA-treated wood structures were generally contaminated with Cr, Cu and As when compared to the background concentration of each metal. In addition, the concentrations of Cr, Cu and As in soils decreased as the vertical and horizontal distance from the structure increased. Further studies should be conducted to evaluate the mobility and distribution of these metals in the environment as well as to develop novel technologies for remediation of CCA contaminated soils.