• Journal of Environmental Health Sciences
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• v.22 no.2
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• pp.25-31
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• 1996

The species of four heavy metals (Cr, Cu, Ni and Pb) associated with sediments (viz exchangeable, carbonates, reducible, organic and residual fractions) were determined with respect to the particle sizes and depths at four locations of the lower Kumho river. In the exchangeable fraction, 3.7~19.52% of Ni and 2.8~14.81% of Pb were found, and in the carbonates fraction 2.12~19.43% of Ni and 1.39~15.42% of Pb were found. The reducible fraction retained about 8.66~44.93% of Cr, 0.41~9.79% of Cu, 17.38~35.74% of Ni and 9.5~44.89% of Pb. In the organic fraction about 0~21.06% of Cr, 2.95~35.74% of Cu, 0~14.66% of Ni and 0~10.65% of Pb were found. The residual fraction retained about 52.6~83.53% of Cr, 63.86~86.39% of Cu, 39.66~66.16% of Ni and 39.97~71.75% of Pb. The order of release or mobility of heavy metals was Ni > Pb > Cr > Cu. Mobile fraction of heavy metals by particle sizes (1.0~0.5 mm and 0.5~0.25 mm) was found to be higher in particle sizes 1.0~0.5 mm than that of 0.5~0.25 mm. The release or mobility of heavy metals by depths (0~5 cm, 5~10 cm and 10~15 cm) was found to be higher in the upper sediments than in the lower sediments, except Cu.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.05a
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• pp.46-51
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• 2000

Environmental quality regulations are used to establish the maximum permissible concentrations of heavy metals before a site can be deemed to be polluted or contaminated. This paper compares the results obtained by 0.IN HCl extraction and acid extraction method(HNO$_3$+HClO$_4$.HCl). The leaching efficiency of 0.1N HCl extraction is directly proportional to the final pH of leachate, due to the different solubilities of the heavy metals at different pH values, The severe differences between 0.1N HCl-extractable and total metal contents result mainly from the buffering effect of carbonates, present in sediment. samples. Application of sequential extraction experiments to some sediments collected from gully pot in Seoul illustrates a much stronger scavenging effect by Fe and Mn-hydroxides, carbonates and organic phases. As deduced from both sequential extraction and leaching experiments, the relative mobility of heavy metals is found to be: Mn>Zn>>Co>Cd>>Cu>Pb>Cr>Fe, in spite of large differences in heavy metal content and localization. Changes in the physicochemical environments (such as acidification) caused by a traffic accident may result in the severe environmental pollution of heavy metals of surrounding area( surface water and rivers).

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.2
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• pp.8-15
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• 2008

Wastewoods (logging residues) generated in Korea were used to make lignocellulosic fillers for papermaking. Lignocellulosic fillers could play great roles to increase retention efficiency and thus decrease turbidity of white water in papermaking process. In addition, lignocellulosic fillers could be used to improve physical properties of paper through their high affinity to cellulosic fibers, leading to the less use of chemical additives like retention aids. Wastewoods including Pinus densiflora and Quercus variabilis were chemically and mechanically treated for making fine particles passing through 100 mesh wire. The newly generated fillers showed larger particle size distribution than ground calcium carbonates but similar distribution to talc. In particular, pretreatment by hot water was more effective to generate smaller particle size than by alkali treatment. Lignocellulosic particles mixed with ground calcium carbonates under intense hybridizing condition greatly contributed to surface coverage of organic fillers in addition to filling to lumen and pits.

• Economic and Environmental Geology
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• v.32 no.1
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• pp.53-62
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• 1999

The possibility of heavy metal pollution by contaminated roadside soils was studied under controlled conditions. The soil samples from roadside and those from a retention pond consisting of settling particles were characterized by the XRD analyses and the sequential extraction experiments. Characterization by sequential extraction, for roadside soil indicates elevate total concentrations of heavy metals. The leaching behavior of the samples under different pH and time conditions were also studied. Differences between both types of samples result mainly from the buffering effect of carbonates, present in roadside soils and lacking from settling particles. Acid leaching of the settling particles is equivalent to the sum of FI+FII+FIII, while the amounts leached from roadside soil are lower probably from kinetic reasons. The buffering effects of carbonates were found to greatly delay the onset of the leaching reactions and the extent of dissolution in most metals except for Ca and Mn. The study of leaching kinetics at pH of 6.5 and 5 showed that Cd and Zn reached the maximum possible concentration within 3 days, while Pb did not show any sign of dissolution at both ph values. The absolute amounts of dissolved Cd and Zn increased by 7 to 9 times by decreasing the pH from 6.5 to 5, indicating slightly acidified rain may result in significant metal dissolution. As deduced from both sequential extraction and leaching experiments, the relative mobility of heavy metals is found to be : Mn=Cd>Zn>>Pb>Fe, in spite of large differences in heavy metal contents and localizations.

• Journal of the Korean Ceramic Society
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• v.18 no.3
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• pp.171-181
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• 1981

Alkaline-earth porcelains have been prepared from mixture of kaolin, quartz, and synthetic calcines obtained by calcining a mixture of kaolin and more than two different kinds of alkaline-earth carbonates. They were magnesium, calcium and barium carbonates which are inexpensive and readily available. The vitrification behavior of the batch mixes was investigated in the firing range of 1240$^{\circ}$to 1380$^{\circ}$, in relation to the body compositions. It appeared that the density and the firing temperature depended largely on the content of alkaline-earth oxides in the body. These porcelains posses excellant dielectric properties, and are especially valuable as bases for deposited carbon resistors for which they were developed. An illustrative composition is 50% Dong Hwa kaolin, 22.4% Chang Shin quartz, 27.6% calcine. The composition of the calcine is 70% Dong Hwa kaolin, 10.7% BaCO3, 13.5% CaCO3, 5.8% MgCO3. The specific resistance of this body is $1.2{\times}10^{15}$ ohm-cm at 5$0^{\circ}C$, $2.5{\times}10^{14}$ ohm-cm 10$0^{\circ}C$, $2.5{\times}10^{13}$ ohm-cm at 15$0^{\circ}C$, $1.8{\times}10^{12}$ohm-cm at 20$0^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.28 no.11
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• pp.2025-2028
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• 2007

Homogeneous zinc tetrahalide complexes, highly active catalysts for the coupling reactions of alkylene oxide and CO2 produce alkylene carbonates, were heterogenized due to their tendency to decompose produced alkylene carbonates during the distillation process. Heterogenization of homogeneous zinc tetrahalide complexes was achieved by polymerizing 1-alkyl-3-vinylimidazolium zinc tetrahalides. These polymerized zinc tetrahalide catalysts displayed similar activities to their corresponding monomeric analogues for the coupling reactions of carbon dioxide with ethylene oxide (EO) or propylene oxide (PO) to produce ethylene carbonate (EC) or propylene carbonate (PC). TGA studies showed that the polymer-supported zinc tetrahalide catalysts are thermally stable up to 320 oC. The catalyst recycle test showed that the supported catalysts could be reused over six times. After removal of the polymer-supported catalyst through a simple filtration, EC was able to be isolated without decomposition.

• Journal of the Mineralogical Society of Korea
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• v.20 no.4
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• pp.255-260
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• 2007

The loess on the Chinese loess plateau is not only the accumulation of Asian dust but also the source materials of Hwangsa. The eolian carbonates of the loess were dissolved and reprecipitated to form secondary pedogenic carbonates by the post-depositional weathering during the interglacial time. Mineralogical analysis shows that the secondary calcites are composed mostly of a nanosized fibrous calcite with rather constant width ($30{\sim}50nm$) and highly variable length. The nano calcite is the major authigenic mineral, which occurs as the fine-grained matrix of the loess and paleosol. The nano calcite was recently reported in the Hwangsa, where it was originated from the source regions of Chinese loess plateau.

• Bulletin of the Korean Chemical Society
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• v.20 no.12
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• pp.1413-1417
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• 1999

Chemical poisoning of Ni/MgO catalyst was induced by hot alkali carbonate vapor in molten carbonate fuel cell (MCFC), and the poisoned (or contaminated) catalyst was characterized by TPR/TPO, FTIR, and XRD analysis. Carbonate electrolytes such as K and Li were transferred to the catalyst during DIR-MCFC operation at 650 ℃. The deposition of alkali species on the catalyst consequently led to physical blocking on catalytic active sites and structural deformation by chemical poisoning. TPR/TPO analysis indicated that K species enhanced the reducibility of NiO thin film over Ni as co-catalyst, and Li species lessened the reducibility of metallic Ni by chemical reaction with MgO. FTIR analysis of the poisoned catalyst did not exhibit the characteristic ${\vector}_1$$(D_{3h})$ peaks (1055 $cm^{-1},\;1085\;cm{-1})$ for pure crystalline carbonates, instead a new peak (1120 $cm^{-1})$ was observed proportionally with deformed alkali carbonates. From XRD analysis, the oxidation of metallic Ni into $Ni_xMg_{1-x}O$ was confirmed by the peak shift of MgO with shrinking of Ni particles. Conclusively, hot alkali species induced both chemical poisoning and physical deposition on Ni/MgO catalyst in DIR-MCFC at 650 ℃.

• Analytical Science and Technology
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• v.12 no.4
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• pp.284-289
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• 1999

Dissolved inorganic carbonates in ground water were quantitatively recovered by using gas evolution method. Gas evolution method was found to be less time-consuming, less susceptible to the contamination fromatmospheric $CO_2$ and little affected by the sulfate ions in comparison to the direct precipitation method. Extraction efficiency of nearly 99% could be achieved by gas evolution method in two hours using recirculated gas at a sweeping rate of 4 liter per minute. Samples for carbon isotope fractionation study were collected in three fractions with collection times. The evolution time for the first fraction was one hours, and then second and third fractions were collected at intervals of 30 minutes, respectively. A small portion of each fraction was analyzed to evaluate ${\delta}^{13}C$ values, which were measured to be -7.9‰, -3.0‰ and +0,4‰ for the each fraction. The result clearly indicated that gas evolution method generates isotopically lighter carbon at the beginning of the purging process and heavier isotopes at the end. However, this isotope fractionation effect could be neglected by the almost complete recovery of carbonates.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.183-197
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• 2022

Geochemical data, including Sr-Nd-Pb-Mg-Zn isotopes, reported on the late Cenozoic intraplate basaltic rocks in the Korean Peninsula (Mt. Baekdu, Jeongok, Baengnyeong Island, Pyeongtaek, Asan, Ganseong, Ulleung Island, Dok Island, and Jeju Island) are summarized to constrain their mantle source lithologies, and the nature of mantle end-members required. In the Sr-Nd isotope correlation diagram, Jeju basalts plot in the field of EM2-type oceanic island basalts (OIB), while the other basalts fall in the EM1-type OIB field. In Pb-Pb isotope space, Jeju basalts show a mixing array between Indian MORB and EM2 component, whereas the other basalts display an array with EM1 component. The Korean basalts were derived from a hybrid source of garnet lherzolite and recycled stagnant slab materials (eclogite/pyroxenite, pelagic sediments, carbonates) in the mantle transition zone. The EM1 component could be ancient (~2.0 Ga) K-hollandite-bearing pelagic sediments that were isolated for a long period in the mantle transition zone due to their neutral buoyancy. The EM2 component might have been relatively young (probably Pacific slab) and recently recycled clay-rich pelagic sediments. Eclogite and carbonates are unlikely to account for the EM components, but they are common in the mantle source of the Korean basalts.