• Journal of Korean Society for Atmospheric Environment
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• v.20 no.6
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• pp.823-832
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• 2004

Atmospheric aerosol particles collected in Seoul on four single days, each in every seasons of 2001, were characterized and classified on the basis of their chemical species using low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA). Low-Z particle EPMA technique can analyze both the size and the chemical species of individual aerosol particles of micrometer size and provide detailed information on the size distribution of each chemical species. The major chemical species observed in Seoul aerosol were aluminosilicate, silicon dioxide, calcium carbonate, organic, carbon-rich, marine originated, and ammonium sulfate particles, etc. The soil originated species, such as aluminosilicate, silicon dioxide, and calcium carbonate were the most popular in the coarse fraction, meanwhile, carbonaceous and ammonium sulfate were the dominant species found in the fine fraction. Marine originated species such as sodium nitrate was frequently encountered, up to 30% of the analyzed aerosol particles.

• Journal of Energy Engineering
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• v.27 no.1
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• pp.59-64
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• 2018

In this paper, we investigated the alternative sources of limestone. Oyster shell waste originated from aquaculture that causes a major disposal landfill problem in coastal sectors in southeast Korea. Their inadequate disposal causes a significant environmental problems araised. Bio mineralization leads to the formation of oyster shells and consists $CaCO_3$ as a major phase with a small amount of organic matter. It is a good alternative material source instead of natural lime stone. The utilization of oyster shell waste for industrial applications instead of natural limestone is major advantage for conservation of natural limestone. The present work describes the limestone and oyster shells hydraulic activity and chemical composition and characteristics are most similar for utilization of oyster shell waste instead of natural limestone.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1945-1948
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• 2012

Rhodamine B (RhB) and rhodamine 6G (Rh6G) were employed as catalysts for the synthesis of cyclic carbonate from carbon dioxide and epoxide. It turned out that the catalytic activity of Rh6G was nearly 29 times higher than that of RhB at 1 atm pressure, $90^{\circ}C$. Furthermore, the catalytic efficiency of RhB and Rh6G was greatly enhanced with triethylamine as co-catalyst. Under the optimized conditions, the best isolated yield (93%) of cyclic carbonate was achieved without organic solvent and metal component.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.814-819
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• 1996

In search of simple host molecules for uranyl ion which form 1: 1-type complexes with high formation constants that can be used either in extraction of uranium from seawater or in catalysis of biologically important organic reactions, the uranophile activities of dihydroxyazobenzene derivative 1 were studied. Uranyl ion and 1 form a 1: 1-type complex with a very large formation constant. The formation constant was measured at pH 7-11.6 by competition experiments with carbonate ion. From the resulting pH dependence, ionization constants of the two aquo ligands coordinated to the uranium of the uranyl complex of 1 were calculated. The ionization constants were also measured by potentiometric titration of the uranyl complex of 1. Based on these results, the pKa values of the two aquo ligands were estimated as 7.1 and 11.0, respectively. At pH 7.5-9.5, therefore, the complex exists mostly as monohydroxo species. Under the conditions of seawater, 1 possesses greater affinity toward uranyl ion compared with other uranophiles such as carbonate ion, calixarene derivatives, or a macrocyclic octacarboxylate. In addition, complexation of 1 with uranyl ion is much faster than that of the calixarene or octacarboxylate uranophiles.

• Macromolecular Research
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• v.16 no.3
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• pp.238-246
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• 2008

A new strategy using protection-deprotection chemistry was used to prepare branched polymers using the ATRP method only. Among the several monomers with different protecting groups, vinyl benzyl t-butyloxy carbonate (VBt-BOC) and 4-methyl styrene (4-MeSt) could be polymerized successfully to form backbones using the ATRP method in a controlled fashion. The protected groups in the backbones were converted to alkyl bromides and used as initiating sites for branch formation. The benzyl t-butyloxy carbonate groups in the backbones containing VBt-BOC units were first deprotected to benzyl alcohol by trifluoroacetic acid, then converted to benzyl bromide by reacting them with triphenylphosphine/carbon tetrabromide. The benzyl bromide groups in the backbones containing 4-MeSt units could be generated by bromination of the methyl groups using N-bromosuccinimide/benzoyl peroxide. The structures of the prepared polymers were well-controlled, as evidenced by the controlled molecular weight as well as the narrow and unimodal molecular weight distribution.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.213-214
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• 2021

External insulation method is used to conserve energy of buildings. However, the current external insulation method uses organic insulating materials to become a diffusion path in case of fire. In this study, the purpose of this study is to provide basic data on the required performance of the plastering material according to the CaCO₃ powder addition of the finishing material of the external insulation method. In Figure 1, when powder was added, the adhesion strength decreased by 30% to 35% at 10% and 0% to 50% at 20% compared to Plain. In Figure 2, the moisture permeability increases approximately twice when powder is added. The results for the water absorption coefficient are shown in Figure 3.

• Ocean and Polar Research
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• v.24 no.2
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• pp.167-175
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• 2002

Sediment from six piston cores from the East Sea (Sea of Japan) was analyzed for evidence of paleoceanographic changes and paleoclimatic variation. A distinct geochemical boundary is evident in major element concentrations and organic carbon content of most cores near the 10-ka horizon. This distinctive basal Holocene change is interpreted to be largely the result of changing sediment sources, an interpretation supported by TiO_2/Al_2O_3$ ratios. Organic carbon and carbonate contents also differ significantly between the Holocene and glacial intervals. The C/N ratio of organic matter is greater than 10 during the glacial period, but is less than 10 for the Holocene, suggesting that the influx of terrigenous organic matter was more volumetrically important than marine organic matter during glacial times. The chemical index of weathering (CIW) is higher for the Holocene than the glacial interval, and changes markedly at the basal Holocene geochemical boundary. Silt fractions are higher in the glacial interval, suggesting a strong effect of climate on silt particle transportation: terrigenous aluminosilicates and continental organic carbon transport were higher during glacial times than during the Holocene. Differences in sediment composition between the Holocene and glacial period are interpreted to have been climatically induced.

• Journal of Ginseng Research
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• v.22 no.3
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• pp.205-210
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• 1998

Glucosidic bonds at the C20 position of the sapogenins were hydrolyzed easily in the lower pH, higher temperatures and longer times to give prosapogenins and sugars. The glucosidic bond of saponin at the C3 of ginsenoside-Rb1, which is secondary carbon, was relatively stable due to the low electron density of -0.2. But the bond of saponin at the C20 position, which is tertiary carbon with the relatively high electron density of -0.3, was liable to be hydrolyzed even in weakly acidic solution by the increase of heating time. On the other hand, red ginseng contained 13.34 mg/g of citric acid, 8.78 mg/g of malonic acid, 3.70 mg/g of oxalic acid, 2.13 mg/g of malic acid and 0.44 mg/g of succinct acid. Ginseng saponins were very stable in ginseng extract neutralized with sodium carbonate or sodium bicarbonate corresponding to the equivalent amount of the total organic acid in the red ginseng.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.45-55
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• 2003

This study investigates the fractional composition and the leaching characteristics of heavy metals in polluted soils due to mining activities. The fractionated composition of heavy metals is classified into five fractions; adsorbed, carbonate, reducible, organic and residual fraction. The status of humic substances in mine wastes of most sites are polyhumic except tailing from Sangdong mine. According to the sequential extraction procedures (SEPs), leaching probabilities of Cd in coal wastes and tailing are relatively low due to high percentage of residual fraction. 46.4% of Ni in tailings from Sangdong mine is probably leached under oxidized environment, and 39.4% of Cu in these tailings is readily extracted under strongly oxidized environment by organic fraction. According to leaching condition of pH 3.0 and pH 5.6, the amount of heavy metals leached out of coal wastes and tailing increases to 1/2 hours. At pH 3.0 and pH 5.6, concentration of Ni in tailing increases up three times of the initial value. Heavy metals released from coal wastes and tailing were not influenced significantly by leaching time.

• Textile Coloration and Finishing
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• v.29 no.4
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• pp.211-222
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• 2017

In this study, we investigated the dyeing properties of the ultra-fine nylon suede non-woven fabric with Sulphur black dye regarding to the effect of dye concentrations, reducing agent contents, sodium carbonate contents, antioxidant contents, immersion temperature and exposure time in air by pad-steam process. The optimal conditions of dyeing for the ultra-fine nylon suede non-woven fabric were determined with dye concentration of 30% o.w.f., reducing agent content of $9{\sim}13g/{\ell}$, sodium carbonate content of $1{\sim}4g/{\ell}$, antioxidant content of $1{\sim}5g/{\ell}$, immersion temperature of $70^{\circ}C$, exposure time of 20 minutes in air and immersion time of 1 minute, respectively. Meanwhile, the colorfastness to washing, the colorfastness to light, and the colorfastness to perspiration for dyed ultra-fine nylon suede non-woven fabric were achieved in the range of 4-5 grades. The formaldehyde and arylamine were not detected on the ultra-fine nylon suede non-woven fabric by KC tests.