• Journal of Environmental Health Sciences
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• v.24 no.2
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• pp.134-144
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• 1998

A comprehensive air quality monitoring was carried out to investigate the criteria concentration of air pollutant in indoor of subway stations of Seoul City. The samples were collected twice per year (the first and the second half of the year) at each sampling point from February to September in 1997. Sampling point of subway stations was ticket office and platform. The measurement of indoor air pollutants such as sulfur dioxide(SO$_2$), nitrogen dioxide(NO$_2$), carbon monoxide(CO), carbon dioxide(CO$_2$), total suspended particulate(TSP) was performed to determine the indoor air quality. Heavy metals(Pb, Cd, Cu, Cr, As, Hg) were also measured together with those air pollutants. The annual average concentration of CO$_2$ and TSP in subway stations were relatively high while those of heavy metals were within 10% of environmental recommended standard concentration in all stations. As results of regression analysis between line and line of air factors, the concentrations of CO, CO$_2$, TSP, Pb, Cd, Cr and Cu were highly correlated, but those of $SO_2, NO_2$ and Hg were not correlated. As results of regression analysis between ticket office and platform, the concentrations of heavy metals such as Cr and Cu were highly correlated. Results of oneway analysis of variance between the first and the second half of the year air factors also indicated that CO, CO$_2$, Cd, Cu, Hg were significant($\alpha$=0.01), respectively. The average contration of total suspended particulate(TSP) in subway line No. 1 was shown high concentration(200 $\mu g/m^3\cdot$ day) level.

• Korean Journal of Environmental Agriculture
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• v.35 no.1
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• pp.79-86
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• 2016

BACKGROUND: This study was initiated to quantitatively evaluate the effects of five heavy metals on the growth and P removal efficiencies of Alcaligenes sp., known as the Phosphorus Accumulating Organisms (PAOs). It was cultivated in the batch system with five heavy metals, such as Cd, Cu, Zn, Pb and Ni, added in single and binary mixtures, respectively.METHODS AND RESULTS: IC₅₀ (half of inhibition concentration of bacterial growth) and EC₅₀ (half of effective concentration of phosphorus removal Efficiencies) were used to quantitatively evaluate the effects of heavy metals on the growth and phosphorus removal Efficiencies of Alcaligenes sp. In addition, Additive Index Value (A.I.V.) method was used to evaluate the interactive effects between Alcaligenes sp. and heavy metals. As a result, as the five heavy metals were singly added to Alcaligenes sp., the greatest inhibitory effects on the growth and P removal efficiencies of each bacteria was observed in the cadmium (Cd). In the binary mixture treatments of heavy metals, the treatments of lowest IC₅₀ and EC₅₀ were the Cd + Cu treatment. Based on the IC₅₀ and EC₅₀ of the binary mixtures of heavy metals treatments, most interactive effects between the heavy metals were found to be antagonistic.CONCLUSION: Based on the results obtained from this study, it appears that they could provide the basic information about the toxic effects of the respective treatments of single and binary mixtures of heavy metals on the growth and P removal efficiencies of Alcaligenes sp. through further study about the characterization of functional proteins involved in toxic effects of heavy metals.

• Electronic Materials Letters
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• v.14 no.6
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• pp.725-732
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• 2018

The thermoelectric and transport properties of Ti-doped FeVSb half-Heusler alloys were studied in this study. $FeV_{1-x}Ti_xSb$ (0.1 < x < 0.5) half-Heusler alloys were synthesized by mechanical alloying process and subsequent vacuum hot pressing. After vacuum hot pressing, a near singe phase with a small fraction of second phase was obtained in this experiment. Investigation of microstructure revealed that both grain and particle sizes were decreased on doping which would influence on thermal conductivity. No foreign elements pick up from the vial was seen during milling process. Thermoelectric properties were investigated as a function of temperature and doping level. The absolute value of Seebeck coefficient showed transition from negative to positive with increasing doping concentrations ($x{\geq}0.3$). Electrical conductivity, Seebeck coefficient and power factor increased with the increasing amount of Ti contents. The lattice thermal conductivity decreased considerably, possibly due to the mass disorder and grain boundary scattering. All of these turned out to increase in power factor significantly. As a result, the thermoelectric figure of merit increased comprehensively with Ti doping for this experiment, resulting in maximum thermoelectric figure of merit for $FeV_{0.7}Ti_{0.3}Sb$ at 658 K.

• Journal of the Mineralogical Society of Korea
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• v.10 no.2
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• pp.139-147
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• 1997

The Janghang smelter is the first lead, zinc and copper smelting facility in Korea which was operated for a half century from 1936 to 1989. The clay minerals and their heavy metal association in the soil profile around the smelter have been studied using XRD, EPMA, SEM-EDS, TEM, EPR and sequential extraction techniques. The soils in A horizon are highly acidic showing pH 4.45. The pH is going up with increasing depth. They have residual water contents of 1.18-1.51 wt%, loss on ignition of 6.32-7.79 wt%, and carbon contents of 0.08-0.88 wt%. Soils consist of quartz, feldspar, muscovite, kaolinite, vermiculite, biotite, chlorite, goethite and hematite in the decreasing abundance. The contents of clay minerals, especially vermiculite and chlorite, decrease with increasing depth. Sequential extraction experiments for the profile samples show that heavy metals (Zn, Cu, Pb, Cd) are highly concentrated in the A horizon of the soil profile as water-extractable (mostly amorphous), MgCl2-extractable (exchangeable in clay minerals), and organic phases. The heavy metal contents decrease with increasing depth. It suggests that the heavy metals are mainly associate with clay minerlas in an exchangeable state. It is also noted that heavy metals are highly concentrated in the manganese and iron oxide phases.

• Korean Journal of Metals and Materials
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• v.48 no.1
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• pp.62-70
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• 2010

Leaching and solvent extraction experiments have been performed to develop a hydrometallurgical process for the recovery of nickel and cobalt from nickel laterite ore with high magnesium content. Most of the nickel and magnesium in the laterite ore dissolved at leaching conditions of $80^{\circ}C$ and 100 g/L sulfuric acid concentration. while half of the cobalt and iron were leached at the same conditions. Solvent extraction experiments were carried out with D2EHPA and saponifed D2EHPA from a synthetic solution containing Ni, Co, and Mg. The extraction percentage of Co, Mg. and Ni by D2EHPA was very low in a pH range of 4.4 to 7.3. while the extraction percentage sharply increased by using saponified D2EHPA. The stripping percentage of the metals from the saponified D2EHPA increased with sulfuric acid concentration and reached 99.9% at 1 M $H_2SO_4$ solution.

• Journal of Powder Materials
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• v.23 no.5
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• pp.348-352
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• 2016

Quantum dots (QDs) are capable of controlling the typical emission and absorption wavelengths because of the bandgap widening effect of nanometer-sized particles. These phosphor particles have been used in optical devices, photovoltaic devices, advanced display devices, and several biomedical complexes. In this study, we synthesize ZnSe QDs with controlled surface defects by a heating-up method. The optical properties of the synthesized particles are analyzed using UV-visible and photoluminescence (PL) measurements. Calculations indicate nearly monodisperse particles with a size of about 5.1 nm at $260^{\circ}C$ (full width at half maximum = 27.7 nm). Furthermore, the study results confirm that successful doping is achieved by adding $Eu^{3+}$ preparing the growth phase of the ZnSe:Eu QDs when heating-up method. Further, we investigate the correlation between the surface defects and the luminescent properties of the QDs.

• Journal of Environmental Science International
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• v.12 no.2
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• pp.201-205
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• 2003

The dechlorination of chlorinated methanes by iron powder and palladium coated iron (Pd/Fe) was studied in batch experiments. Iron powder dechlorinated carbon tetrachloride (CT) with a half-life of 4 days. Three chloromethane was found as major product and less chlorinated daughters. Mass balance found was to be about 93-99%. Pd/Fe showed very enhanced reactivity for CT in comparing with plain iron. The major dechlorination products of CT were also less chlorinated methanes with Pd/Fe. Pd/Fe also degrade the produced less chlorinated compounds. Sequential reactions were occurred on Pd/Fe. As the Pd/Fe content increased, the reaction rate was increased linearly.

• Korean Journal of Metals and Materials
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• v.47 no.6
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• pp.378-382
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• 2009

We investigated the effects of deposition conditions on the fabrication of $Fe_{3}O_{4}$ thin films using a reactive DC magnetron sputtering at room temperature. The structural, electrical, and magnetic properties of Fe oxide films dependence on the film thickness, oxygen flow rate, and the substrate crystallinity were also studied. We have successfully fabricated $Fe_{3}O_{4}$ film with thickness of about 10 nm under optimal reactive sputtering conditions. The saturation magnetization, resistivity, and Verwey transition of the $Fe_{3}O_{4}$ film were298 emu/cc, $4.0{\times}10^{-2}{\Omega}cm$, and 125 K, respectively.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.268-274
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• 2010

Emission of heavy metals as hazardous air pollutants has been focused with tightening regulatory limits due to their hazardousness. Measurements and characteristic investigations of heavy metals emitted from a commercial power plant burning anthracite coal have been carried out. The plant consists of a circulating fluidized bed combustor, a cyclone, a boiler and an electrostatic precipitator(ESP) in series. Dust and gaseous samples were collected to measure main heavy metals including gaseous mercury before ESP and at stack. Dust emissions as total particulate matter (TPM), PM-10 and PM-2.5 at inlet of ESP were very high with 23,274, 9,555 and $7,790mg/Sm^3$, respectively, as expected, which is much higher than those from pulverized coal power plants. However TPM at stack was less than $0.16mg/Sm^3$, due to high dust removal efficiency by ESP. Similarly heavy metals emission showed high collection efficiency across ESP. From particle size distribution and metal enrichment in sizes, several metal concentrations could be correlated with particle size showing more enrichment in smaller particles. Mercury unlike other solid metals behaved differently by emitting as gaseous state due to high volatility. Removal of mercury was quite less than other metals due to it's volatility, which was 68% only. Across ESP, speciation change of mercury from elemental to oxidized was clearly shown so that elemental mercury was half of total mercury at stack unlike other coal power plants which equipped wet a scrubber.

• Journal of the Korean Magnetics Society
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• v.23 no.6
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• pp.179-183
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• 2013

The half-metallicity and magnetism for compounds of the $N_{(2-0.5n)}O_{0.5}nKCa$ (n = 0~4), which was based on the $d^0$ Heusler half-metals of $N_2KCa$ and $O_2KCa$, were investigated by means of first-principles band calculation method. From the calculated total magnetic moments and the density of states, we found that these three compounds have the half-metallicity. The magnetic moments of the N and O atoms in these compounds were considerably increased compared to those of pure $N_2KCa$ and $O_2KCa$. The K atoms have a large negative magnetic moments. The relationship between the value of magnetic moments for each atom and density of states are discussed.