• Resources Recycling
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• 제30권6호
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• pp.76-82
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• 2021

The separation of palladium from crude metal, which is obtained from electronic waste using pyrometallurgy was achieved through electrolysis. This was done to recover high-purity copper. The oxidation potentials of these metals are a fundamental part of the analysis of electrolytic separation of palladium and impurity metals. To achieve this, copper, iron, and nickel were dissolved in the electrolyte, and palladium and aluminum were found to be recoverable from anode slime. During the electrolysis for palladium separation, palladium was present in the anode slime and was obtained with a recovery of 97.46 % indicating almost no loss. 4N-grade copper was recovered from the electrodeposition layer at the cathode.

• Journal of the Korean Chemical Society
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• 제63권1호
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• pp.37-44
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• 2019

N,N'-bis(ethyldihydrogen phosphate)-1,4,5,8-naphthalene bis(dicarboximide) (EPNI) and N,N'-bis(ethyldihydrogen phosphate)-3,4,9,10-perylene bis(dicarboximide) (EPPI) and their zirconium bisphosphate multilayers (Zr-EPNI and Zr-EPPI), that had been briefly reported by us, were further investigated in terms of their electrochemical properties. EPNI in aqueous solution showed typical two reversible reductions at ITO electrode but the reductions were strongly dependent on solution pH while EPPI showed only an irreversible reduction. The single and mixed multilayers of Zr-EPNI and Zr-EPPI were well constructed on ITO electrode by the alternate adsorptions of zirconium ion and the bisimides. While Zr-EPNI multilayer on ITO electrode showed single broad reversible reduction with $E_{1/2}=-0.68V$, Zr-EPPI gave two separated reductions at $E_{1/2}=-0.54$ and -0.81 V vs SCE, quite differently from the solution properties. The average layer densities of the multilayers were estimated as $1.5{\times}10^{-10}$ and $2.3{\times}10^{-10}mol/cm^2$ for Zr-EPNI and Zr-EPPI, respectively. Both the monolayers of Zr-EPNI and Zr-EPPI could not completely block the electron transfer between $Fe(CN){_6}^{3-}$ in solution and ITO electrode but 3-5 layers of Zr-EPNI and Zr-EPPI could block it completely and mediated the one-way electron transfer at the potential shifted to their reduction potentials. When the monolayer of zirconium 1,10-decanediylbisphosphonate (Zr-DBP) was used as a sublayer of Zr-EPNI and Zr-EPPI layers, the mediated electron transfer became prominent without any direct electron transfer.

• Korean Journal of Materials Research
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• 제29권9호
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• pp.519-524
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• 2019

Spherical $Li_3V_2(PO_4)_3$ (LVP) and carbon-coated LVP with a monoclinic phase for the cathode materials are synthesized by a hydrothermal method using $N_2H_4$ as the reducing agent and saccharose as the carbon source. The results show that single phase monoclinic LVP without impurity phases such as $LiV(P_2O_7)$, $Li(VO)(PO_4)$ and $Li_3(PO_4)$ can be obtained after calcination at $800^{\circ}C$ for 4 h. SEM and TEM images show that the particle sizes are $0.5{\sim}2{\mu}m$ and the thickness of the amorphous carbon layer is approximately 3~4 nm. CV curves for the test cell are recorded in the potential ranges of 3.0~4.3 V and 3.0~4.8 V at a scan rate of $0.01mV\;s^{-1}$ and at room temperature. At potentials between 3.0 and 4.8 V, the third $Li^+$ ions from the carbon-coated LVP can be completely extracted, at voltages close to 4.51 V. The carbon-coated LVP exhibits an initial specific discharge capacity of $118mAh\;g^{-1}$ in the voltage region of 3.0 to 4.3 V at a current rate of 0.2 C. The results indicate that the reducing agent and carbon source can affect the crystal structure and electrochemical properties of the cathode materials.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.1-33
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• 1997

The objective of this study was to analyze the in vitro and in vivo corrosion products of low and high copper amalgams. The four different types of amalgam alloy used in this study were Fine cut, Caulk spherical, Dispersalloy, and Tytin. After each amalgam alloy and Hg were triturated according to the directions of the manufacturer by means of the mechanical amalgamator(Amalgam mixer. Shinhung Co. Korea), the triturated mass was inserted into a cylindrical metal mold which was 12mm in diameter and 10mm in height. The mass was condensed by 150Kg/cm compressive force. The specimen was removed from the mold and aged at room temperature for about seven days. The standard surface preparation was routinely carried out by emery paper polishing under running water. In vitro amalgam specimens were potentiostatically polarized ten times in a normal saline solution at $37^{\circ}C$(potentiostat : HA-301. Hukuto Denko Corp. Japan). Each specimen was subjected to anodic polarization scan within the potential range -1700mV to+400mV(SCE). After corrosion tests, anodic polarization curves and corrosion potentials were obtained. The amount of component elements dissolved from amalgams into solution was measured three times by ICP AES(Inductive Coupled Plasma Atomic Emission Spectrometry: Plasma 40. Perkim Elmer Co. U.S.A.). The four different types of amalgam were filled in occlusal and buccal class I cavities of four human 3rd molars. After about five years the restorations were carefully removed after tooth extraction to preserve the structural details including the deteriorated margins. The occlusal surface, amalgam-tooth interface and the fractured surface of in vivo amalgam corrosion products were analyzed. In vivo and in vitro amalgam specimens were examined and analyzed metallographically by SEM(Scanning Electron Microscope: JSM 840. Jeol Co. Japan) and EDAX(Energy Dispersive Micro X-ray Analyser: JSM 840. Jeol Co. Japan). 1. The following results are obtained from in vitro corrosion tests. 1) Corrosion potentials of all amalgams became more noble after ten times passing through the in vitro corrosion test compared to first time. 2) After times through the test, released Cu concentration in saline solution was almost equal but highest in Fine cut. Ag and Hg ion concentration was highest in Caulk spherical and Sn was highest in Dispersalloy. 3) Analyses of surface corrosion products in vitro reveal the following results. a)The corroded surface of Caulk spherical has Na-Sn-Cl containing clusters of $5{\mu}m$ needle-like crystals and oval shapes of Sn-Cl phase, polyhedral Sn oxide phase. b)In Fine cut, there appeared to be a large Sn containing phase, surrounded by many Cu-Sn phases of $1{\mu}m$ granular shapes. c)Dispersalloy was covered by a thick reticular layer which contained Zn-Cl phase. d)In Tytin, a very thin, corroded layer had formed with irregularly growing Sn-Cl phases that looked like a stack of plates. 2. The following results are obtained by an analysis of in vivo amalgam corrosion products. 1) Occlusal surfaces of all amalgams were covered by thick amorphous layers containing Ca-P elements which were abraded by occlusal force. 2) In tooth-amalgam interface, Ca-P containing products were examined in all amalgams but were most clearly seen in low copper amalgams. 3) Sn oxide appeared as a polyhedral shape in internal space in Caulk spherical and Fine cut. 4) Apical pyramidal shaped Sn oxide and curved plate-like Sn-Cl phases resulted in Dispersalloy. 5) In Tytin, Sn oxide and Sn hydroxide were not seen but polyhedral Ag-Hg phase crystal appeared in internal space which assumed a ${\beta}_l$ phase.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제33권5호
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• pp.448-454
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• 2000

This study was to examine the physicochemical characteristics of coagulation reaction between ignited oyster shell powder (IOSP) and red tide organisms (RTO), and its feasibility, in developing a technology for the removal of RTO bloom in coastal sea,IOSP was made from oyster shell and its physicochemical characteristics were examined for particle size distribution, surface characteristic by scanning electron microscope, zeta potential, and alkalinity and pH variations in sea water. Two kinds of RTO that were used in this study, Cylindrotheca closterium and Skeletonema costatum, were sampled in Masan bay and were cultured in laboratory. Coagulation experiments were conducted using various c(Incentrations of IOSP, RTO, and a jar tester. The supernatant and RTO culture solution were analyzed for pH, alkalinity, RTO cell number, IOSP showed positive zeta potentials of $11.1{\~}50.1\;mV\;at\;pH\;6.2{\~}12.7$, A positive zeta potential of IOSP slowly decreased with decreasing pNa 4,0 to 2,0. When pNa reached zero, the zeta potential approached zero, When a pMg value was decreased, the positive zeta potential of IOSP increased until pMg 3.0 and decreased below pMg 3.0. IOSP showed 4.8 mV of positive zeta potential while RTO showed -9.2 mV of negative zeta potential in sea water. A positive-negative EDL (electrical double-layer) interaction occurred between $Mg(OH)_2$ adsorption layer of IOSP and RTO in sea water so that EDL attractive force always worked between them. Hence, their coagulation reaction occurred at primary minimum on which an extreme attractive force acted because of charge neutralization by $Mg(OH)_2$ adsorption layer of IOSP. As a result, the coagulation reaction was rapidly processed and was irreversible according to DLVO (Deriaguin-Landau-Verwey-Overbeek) theory. Removal rates of RTO were exponentially increased with increasing both IOSP concentration and G-value. The removal rates were steeply increased until 50 mg/l of IOSP and reached $100{\%}\;at\;400\;mg/l$ of IOSP. Removal rates of RTO were $70.5,\;70.5,\;81.7,\;85.3{\%}$ for G-values of $1,\;6,\;29,\;139\;sec^(-1)$at IOSP 100 mg/l, respectively. This indicated that mixing (i.e., collision among particles) was very important for a coagulation reaction.

• Journal of the Korean Electrochemical Society
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• 제6권4호
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• pp.255-260
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• 2003

The complex capacitance analysis was performed in order to examine the potential-dependent EDLC characteristics of porous carbon electrodes. The imaginary capacitance profiles $(C_{im}\;vs.\;log\lf)$ were theoretically derived for a cylindrical pore and further extended to multiple pore systems. Two important electrochemical parameters in EDLC can be estimated from the peak-shaped imaginary capacitance plots: total capacitance from the peak area and $\alpha_0$ from the peak position. Using this method, the variation of capacitance and ion conductivity in pores can be traced as a function of electric potential. The electrochemical impedance spectroscopy was recorded on the mesoporous carbon electrode as a function of electric potential and analyzed by complex capacitance method. The capacitance values obtained from the peak area showed a maximum at 0.3V (vs. SCE), which was in accordance with cyclic voltammetry result. The ionic conductivity in pores calculated from the peak position showed a maximum at 0.2 V (vs. SCE), then decreased with an increase in potential. This behavior seems due to the enhanced electrostatic interaction between ion and surface charge that becomes enriched at more positive potentials.

• Korean Journal of Soil Science and Fertilizer
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• 제34권1호
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• pp.26-32
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• 2001

Influence of various rates of fractionated raw cow manure on hydraulic conductivity of the soil was observed. The fractionated raw cow manure(hereafter as FRCM) incorporated into soil. The hydraulic conductivity was measured for the double-layered soil while maintaining the water head by 5 cm over the soil surface. The influence on the mobility of $NO_3{^-}$-N transformed from the FRCM was analyzed. The upper layers (Wolgok series) were made with FRCM ranging from 0% to 10.4 % on weight basis for air-dried soil while the organic matter in the bottom layers (Chungwon series) was removed by combustion. The initial bulk densities for both layers were adjusted to $1.25g\;cm^{-3}$. In this experiment the $K_{sat}$ for the upper layer gradually decreased from $4.71{\times}10^{-3}cm\;min^{-1}$ to $1.2{\times}10^{-3}cm\;min^{-1}$ with increasing the rate of the FRCM from 0 % to 10.4%, while the Ksat of the bottom layer was maintained as $3.7cm\;min^{-1}$. For the double-layered soil columns, the $K_{sat}$ decreased with increasing rate of FRCM at the upper layer from $1.7{\times}10^{-3}cm\;min^{-1}$ to $8{\times}10^{-4}cm\;min^{-1}$ as the rate of organic matter increased from 0 % to 10.4 %, while it took almost 7 days to 64 days to obtain the steady state $K_{sat}$ The elution patterns of $NO_3{^-}$-N and $NH_4{^+}$-N showed that the amounts of both $NO_3{^-}$-N and $NH_4{^+}$-N rapidly approached to the maximum ranging from $14.8mmol_c\;kg^{-1}$ to $0.58mmol_c\;kg^{-1}$ as the rate of FRCM decreased from 10.7 % to 0 % which is equivalent to indigenous amount of $NO_3{^-}$-N and $NH_4{^+}$-N. And the amounts of $NO_3{^-}$-N were approximately three or four time than those of $NH_4{^+}$-N, indicating that the transformation rate of $NO_3{^-}$-N was improved by the higher FRCM rate. Thus, the ability of a soil to supply N can be predicted from its mineralization parameters and leaching potentials influenced by water flow regime in soil.

• The Korean Journal of Physiology and Pharmacology
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• 제1권6호
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• pp.681-690
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• 1997

Loss of synaptic transmission and accumulation of extracellular $K^+([K^+]_O)$ are the key features in ischemic brain damage. Here, we examined the effects of several $K^+$channel modulators on the early ischemic changes in population spike (PS) and $[K^+]_o$ in the CA1 pyramidal layer of the rat hippocampal slice using electrophysiological techniques. After onset of anoxic aglycemia (AA), orthodromic field potentials decreased and disappeared in $3.3{\pm}0.22\;min$ $(mean{\pm}SEM,\;n=40)$. The hypoxic injury potential (HIP), a transient recovery of PS appeared at $6.0{\pm}0.25\;min$ (n=40) in most slices during AA and lasted for $3.3{\pm}0.43\;min$. $[K^+]_o$ increased initially at a rate of 0.43 mM/min (Phase 1) and later at a much faster rate (12.45 mM/min, Phase 2). The beginning of Phase 2 was invariably coincided with the disappearance of HIP. Among $K^+$ channel modulators tested such as 4-aminopyridine (0.03, 0.3 mM), tetraethylammonium (0.1 mM), NS1619 $(0.3{\sim}10\;{\mu}M)$, niflumic acid (0.1 mM), glibenclamide $(40\;{\mu}M)$, tolbutamide $(300\;{\mu}M)$ and pinacidil $(100\;{\mu}M)$, only 4-aminopyridine (0.3 mM) induced slight increase of $[K^+]_o$ during Phase 1. However, none of the above agents modulated the pattern of Phase 2 in $[K^+]_o$ in response to AA. Taken together, the experimental data suggest that 4-aminopyridine-sensitive $K^+$channels, large conductance $Ca^{2+}-activated$ $K^+$ channels and ATP-sensitive $K^+$ channels may not be the major contributors to the sudden increase of $[K^+]_o$ during the early stage of brain ischemia, suggesting the presence of other routes of $K^+$ efflux during brain ischemia.

• Journal of Life Science
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• 제16권3호
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• pp.369-374
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• 2006

Six fractions of Salvia miltiorrhiza were tested for their chemopreventive potentials using biochemical markers of carcinogenesis such as quinone reductase (QR), glutathione S-transferase (GST) and glutathione (GSH). Seventy percentage of EtOH extract was potent inducer of QR activity in Hepa1c1c7 murine hepatoma cells. GST activity was increased about 1.4-fold with EtOAc extract at concentration of 50 ${\mu}g/ml$. GSH levels were significantly increased with $H_2O$ extract, 70% EtOH extract and water extract at concentration of 50 ${\mu}g/ml$ (p<0.005). From these results, 70% EtOH extract (250 mg/kg) was intragastrically administered to ICR mice for 14 days. QR, GST and GSH levels were significantly increased with the 70% EtOH treatment. These studies suggest that the 70% EtOH extract of S. miltiorrhiza could be considered as a potential agent for cancer chemoprevention.

• Journal of Korean Society of Steel Construction
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• 제16권4호통권71호
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• pp.415-423
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• 2004

To investigate the long-term corrosion resistance of an uncoated weathering steel, an important outdoor constructional steel material, skyward surfaces of the weathering steel and a control steel initially exposed to rural and industrial atmospheres for 9 years were electrochemically tested in neutral artificial rain in terms of electrochemical potentials, impedances, and anodic potentiodynamic polarization curves. Their results were then discussed. A quite passive and stable rust layer to the artificial rain was well formed on the skyward surface of the weathering steel exposed to the industrial and rural atmospheres, and its corrosion rate in the artificial rain was measured to be about a low $3{{\mu}m}/y$. Continuous immersion of all the weathered surfaces in the artificial rain revealed the gradual degradation of the weathered corrosion layers on the steel, resulting in a cathodically controlled corrosion of the substrate steel by the electrochemical measurements. Alloy components of the weathering steel were found to retard the degradation of the weathered corrosion layers on the steel in the artificial rain. For better corrosion evaluation of the weathering steel, more electrochemical measurements of surfaces that have been exposed for more than 9 years to more closely simulated atmospheric waters are needed. These measurements are almost non-destructive and can provide online and in situ information on the corrosion rate, the development of corrosion and the conditions of rust layers on any interested surface and at any exposure time of the steel, so they can be effectively applicable to the corrosion evaluation of steel structures such as bridges, towers, and architectures by forming an electrochemical cell on an interested structural surface and by using a portable electrochemical instrument.