• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.307-310
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• 2004

Micellar enhanced ultrafiltration (MEUF) is a surfactant-based separation process and it can remove heavy metal ions from aqueous stream effectively. However, it is necessary to recover and reuse surfactants for economic feasibility because surfactant is expensive. Foam fractionation was investigated for both anionic and cationic surfactant recovery. Chelating agent such as ethylenediaminetetraacetic acid (EDTA) was studied for the separation of heavy metals from surfactant solution. Anionic surfactants bound with heavy metals can be recovered by lowering pH (acidification). In this study, citric acid and imminodiacetic acid (IDA) were applied to release copper from sodium dodecyl sulfate (SDS) micellar solution and compared with EDTA. Precipitation of copper by ferricynide and sodium sulfide were also investigated. As a result, ca. 100 % of copper was released from SDS micellar solution by 5 mM of EDTA and citric acid. And 3.3 mM of ferricyanide formed precipitate with 82.7 % of copper. 5 mM of IDA and sodium sulfide released or formed precipitate 82.5 % and 58.9 % of copper, respectively. Citric acid is harmless to environments and ferricyanide precipitates with Cu easily. Therefore, it is considered that citric acid and ferricyanide have competiveness over a famous chelating agent, EDTA, for the separation of Cu from SDS solution.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.6
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• pp.674-681
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• 2008

Silver as a metal catalyst has been used to remove odorous compounds. In this study, silver particles in nano sizes ($5{\sim}30nm$) were prepared on the surface of $NaHCO_3$, the supporting material, using a sputtering method. The silver nano-particles were dispersed by dissolving $Ag-NaHCO_3$ into water, and the dispersed silver nano-particles in the aqueous phase was applied to remove inorganic odor compounds, $NH_3$ and ${H_2}O$, in a scrubbing reactor. Since ammonia has high solubility, it was removed from the gas phase even by spraying water in the scrubber. However, the concentration of nitrate (${NO_3}^-$) ion increased only in the silver nano-particle solution, implying that the silver nano-particles oxidized ammonia. Hydrogen sulfide in the gas phase was rapidly removed by the silver nano-particles, and the concentration of sulfate (${SO_4}^{2-}$) ion increased with time due to the oxidation reaction by silver. As a result, the silver nano-particles in the aqueous solution can be successfully applied to remove odorous compounds without adding additional energy sources and producing any harmful byproducts.

• Corrosion Science and Technology
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• v.4 no.1
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• pp.19-22
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• 2005

Two Au-Ag-Cu-Pd dental casting alloys (Au:12% and 20%) used. The test solutions used 0.9 % NaCl solution (isotonic sodium chloride solution), 0.9 % NaCl solution containing 1 % lactic acid, and 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_2S$. The surface of two samples in three sample solutions was not natural discoloration during one year. The alloy containing 12 % gold was easily alloyed and the composition was uniform comparing with the alloy containing 20 % gold. The rest potentials have not a little effect after three months. The kinds of metals could not definitely from the oxidation and reduction waves of metal on the cyclic voltammograms. The dissolutions of gold and palladium were 12 % Au sample in the 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_{2}S$. The pH of solution had an affect on dissolution of copper, and sulfur ion had an affect on dissolution of silver. The copper dissolved amount from 20 % gold sample was about 26 times comparing with that of 12 % gold sample in the 0.9 % solution containing 1 % lactic acid. Corrosion products were silver chloride and copper chloride in NaCl solution, and silver sulfide and copper sulfide in NaCl solution containing $Na_{2}S$.

• Journal of the korean society of oceanography
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• v.36 no.1
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• pp.9-18
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• 2001

Chemical speciation of five heavy metals (Cr, Cu, Ni, Pb, Zn) has been analyzed from 37 surface and 2 core sediments of Kyeonggi Bay, using the modified sequential extraction method based on Tessier et at. (1979). The results show that heavy metals in the Kyeonggi Bay surface sediments are associated dominantly with the crystal lattice fraction. But in the polluted sediments of the Incheon North Harbor, the importance of the labile fractions increased while that of the lattice fraction decreased. In particular, the adsorbed and the easily reducible fractions showed a noticeable increase. In the core samples emerged a speciation pattern which differed significantly from that of the surface sediments. A sharp increase in the percentage of the reducible and organic/sulfide fractions and a decrease in the lattice fraction were observed. Throughout the vertical column, however, the metal contents in the lattice fraction showed stability while those of the labile fractions showed an upward increase. The strong association of heavy metals with the organic/sulfide fraction could be attributed in part to the sulfate reduction prevailing in the polluted harbor sediments.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3218-3224
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• 2012

Uniform and well dispersed metal sulfide semiconductor nanoparticles incorporated into matrices of alginate biopolymer are prepared by using a facile in situ method. The reaction was accomplished by impregnation of alginate with divalent metal ions followed by reaction with thioacetamide. XRD analysis showed that the nanoparticles incorporated in the polymer matrix were of cubic structure with the average particle diameter of 1.8 to 4.8 nm. Field emission scanning electron microscopy and high resolution transmission electron microscopy images indicated that the particles were well dispersed and distributed uniformly in the matrices of alginate polymer. FT-IR spectra confirmed the presence of alginate in the nanocomposite. The crystalline nature and thermal stability of the alginate polymer was found to be influenced by the nature of the divalent metal ions used for the synthesis. The proposed method is considered to be a simple and greener approach for large scale synthesis of uniform sized nanoparticles.

• Journal of the Speleological Society of Korea
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• no.92
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• pp.9-18
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• 2009

A number of closed metal mines act as point sources of contamination on nearby streams, soils and plants in our country. The contamination of twelve decomposed samples had earned from nine closed metal mines had been evaluated by TEA-3000. The contents of heavy metal with ion fraction exchange and carbonate fraction forms had been showed that the speciation of heavy metals represented with easy solubility, mobility and bioavailable of plants, and in case of sulfide compounds and organic residuals forms are related with the speciation of metals which may be stable forms because of strong bindable capacity. Also heavy metals elements in mosts of mines got with relative stable within crystal lattice, but results of trace element analyser showed that, in the most of tailings from mine areas, large portions of concentration of heavy metals were explained as stable from, sulfides/ organics and residual. In tailing from Imchun mines, the concentrations extracted by water were relatively high as compared with other mine areas whose total concentrations were very high because of large quantities of exchangeable ions and carbonates and low soil pH. Danger Index (D.I.) suggested in this study was based on the cumulative concentrations of step 1 and 2 from the result of trace element analyser. When the soil pH was considered, this index became better indicator to determine the priority for the remediation of mine area.

• Korean Journal of Environmental Biology
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• v.20 no.2
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• pp.136-145
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• 2002

A laboratory microcosm experiment was conducted to evaluate a major metal uptake route as well as chronic toxic effects of the clam, Macoma balthica exposed to Ag and Cu contaminated sediments. Twenty five clams were exposed to the sediments contaminated with four levels of Ag $Ag(0.01-0.87\mu{mol}\;g^{-1})$ and $Cu(0.75-5.55\mu{mol\;g^{-1})$ for 90 days. AVS (acid volatile sulfide) concentration in the sediments, considered as major factor controlling metal geochemistry and bioavailability, was manipulated to evaluate its effects on Ag and Cu bioaccumulation in M. balthica. Following 90-d exposure, the tissue Ag and Cu in M. balthica increased linearly with the Ag and Cu concentrations in sediments extracted with 1 N HCI (SEM, simultaneously extracted metals with AVS). The bioaccumulation of Ag and Cu in M. balthica was little influenced by difference in [SEM] - [AVS] values, suggesting a minor contribution of pore water metals to bioaccumulation. Tissue Ag and Cu concentrations directly influenced on the clearance rate and glycogen content of the clams. The clams with highest tissue Ag $(1.0\pm{0.2}\mu{mol}\;g^{-1})$ and Cu concentrations $(2.7\pm{0.3}\;\mu{mol}\;g^{-1})$ had only 18-43% of clearance of the clams exposed to uncontaminated sediments. Similarly, glycogen content of the exposed clams had a inverse relationship with tissue Ag and Cu concentrations. These results suggest that M. balthica exposed to Ag and Cu contaminated sediments accumulates metals largely by ingestion of contaminated sediments and can display chronic effects as reduced clearance rate and glycogen content.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.806-812
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• 2008

The ammonia decomposition reaction has been of increasing interest as a means of treating ammonia in flue gas in the presence of precious metal catalyst. Various catalysts, $Pt-Rh/Al_2O_3$, $Pt-Rh/TiO_2$, $Pt-Rh/ZrO_2$, $Pt-Pd/Al_2O_3$, $Pd-Rh/Al_2O_3$, $Pd-Rh/TiO_2$, $Pd-Rh/ZrO_2$, $Pt-Pd-Rh/Al_2O_3$, $Pd/Ga-Al_2O_3$, $Rh/Ga-Al_2O_3$, and Ru/Ga-$Al_2O_3$, were synthesized by using excess wet impregnation method. Using a homemade 1/4" reactor at $10,000{\sim}50,000hr^{-1}$ of space velocity in the presence of precious metal catalyst ammonia decomposition reactions were carried out to investigate the catalyst activity. The inlet ammonia concentration was maintained at 2,000 ppm, with an air balance. Both $T_{50}$ and $T_{90}$, defined as the temperatures where 50% and 90% of ammonia, respectively, are converted, decreased significantly when alumina-supported catalysts were applied. In terms of catalytic performance on the ammonia conversion in the presence of hydrogen sulfide, $Pt-Rh/Al_2O_3$ catalyst showed no effect on the poisoning caused by hydrogen sulfide. These results indicate that platinum-rhodium bimetallic catalyst is a useful catalyst for ammonia decomposition.

• Journal of the Korean earth science society
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• v.24 no.5
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• pp.477-490
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• 2003

Bottom sediments from Youngil Bay, East Coast of Korea, were analyzed for grain composition as well as elemental compositions and total organic carbon (TOC) content in order to investigate the spatial variability and content of metal elements. Grain size distribution of the sediments seems to be controlled by anticlockwise current pattern with bottom topography of the study area. Spatial variability of TOC and all elemental contents reflects those of grain size, but an exception was found in the harbor area (Old-Port): their contents are high in the central part of the bay with the muddy sediment and decrease toward the sand-dominated coastal zone. However, contents of Ca, Sr, K are high in the sand-dominated coastal zone and contents of some heavy metals (Cd, Cu, Zn) are high in the Old-Port area and the mouth of Hyeongsan River. The correlation matrix and R-mode factor analyses reveal that four important factors controlling the distribution of metals in the bay are sediment grain size (or quartz dilution effect), the formation of sulfide minerals associated with decomposition of organic matters under anoxic geochemical environment, calcium carbonate (mainly shell fragments) and coarse-grained feldspar mineral. According to the metal content of labile fraction an CER (concentration enrichment ratio) value, high accumulation of some heavy metals in the harbor area seems to result not formed by early diagenetic processes under anoxic environment.

• Resources Recycling
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• v.15 no.5 s.73
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• pp.3-10
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• 2006

The solvent extraction for the separation of platinum group metals from the leach liquor of spent automotive catalysts has been studied. Tri-n-butyl phosphate (TBP), tri-n-octylamine (TOA) and di-n-hexyl sulfide (DHS) were used as extractants and kerosene as a diluent. The extraction behavior of platinum, palladium and rhodium has been investigated as functions of different kinds of extractants and their concentrations. In addition, the extraction behavior of the major metal impurities such as cerium, lead, iron, magnesium and aluminum has been investigated. Platinum and palladium were extracted with TBP. And platinum, palladium and rhodium were extracted with TOA. Platinum was co-extracted with palladium into the organic phase by solvent extraction using SFI-6 of DHS extractant, but only palladium was selectively extracted with SFI-6R. The selective extraction of palladium with SFI-6R was found better than that with SFI-6, but the kinetics of extraction with SFI-6R was found poor in comparison to SFI-6. The metal impurities extracted simultaneously during the extraction of platinum group metals should be removed in scrubbing and stripping processes. A suitable process has been proposed for the separation of platinum group metals from the leach liquor of spent automotive catalysts. Initially palladium was extracted with SFI-6R, followed by the separation of platinum with TBP or TOA leaving rhodium in the raffinate.