• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.123-130
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• 2005

Zeolite X adsorbents with large surface area were prepared for using oxygen PSA adsorbent. Selective adsorption performance of nitrogen on the synthesized zeolite X adsorbent was improved by the cation exchange of adsorbent. The zeolite X which had over $650m^2/g$ surface area was synthesized at the conditions of $SiO_2\;:\;Na_2O\;:\;H_2O\;:\;Al_2O_3$ = 2.5 : 3.5 : 150 : 1 mole ratio, $98^{\circ}C$ temperature and 18 h synthesized time in 50 L reactor. The metal ions Li, Ag, Ca, Br, Sr, etc. were investigated for ion exchange with zeolite X. Ag ion was showed the highest ion exchange rate among these metal ions and all metal ions were exchanged with Na ion at equivalent rate. Compared with the NaX adsorbent, the ion exchanged zeolite X adsorbent remarkably improved its adsorption performance of nitrogen at the conditions of $10{\sim}40^{\circ}C$ temperature and 0~9 atm pressure. At an equilibrium pressure under 0.5 atm, adsorption performance of nitrogen on the ion exchanged zeolite adsorbent increased in the order of Ag > Li > Ca > Sr> Ba > K, whereas at an equilibrium pressure over 1 atm showed in the order of Li > Ag > Ca > Sr > Ba > K. Nitrogen/oxygen separation factor of Li ion exchanged zeolite X adsorbent was 13.023 at the partial pressure of nitrogen/oxygen gas mixture similar to air and $20^{\circ}C$ adsorption temperature.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.4
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• pp.237-242
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• 2011

In this study, the catalytic activity of Mn-Phthalocyanine (Mn-PC) for VOCs (acetadehyde, propionaldehyde and toluene) combustion was determined. The reaction was carried out in a fixed bed reactor at the temperature range of $200{\sim}380^{\circ}C$. We investigated the physicochemical properties of Mn-PC before and after the pretreatment (air, $450^{\circ}C$, 1 hr, 60 cc/min) by TGA (Thermogravimetric Analyzer), BET (Brunauer Emmett Teller), EA (Elemental Analyzer), XRD (X-ray Diffractometer) and SEM (Scanning Electronic Microscope). By TGA analysis, 88 wt.% mass loss of Mn-PC was found at $419^{\circ}C$. The BET surface area of Mn-PC increased after the pretreatment. The decomposition and combustion of organic components in Mn-PC were observed by EA analysis. We also confirmed that Mn-PC had transformed into a new manganese oxide phase ($Mn_3O_4$) after the pretreatment by XRD analysis. By SEM analysis, many of the micropores generated during the pretreatment were found. The catalytic activity of Mn-PC with the pretreatment for propionaldehyde combustion was higher than that of $Mn_3O_4$ and fresh Mn-PC. It showed the catalytic activity of Mn-PC with the pretreatment for VOCs combustion by the order of toluene < acetadehyde < propionaldehyde.

• Korean Journal of Environmental Agriculture
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• v.25 no.3
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• pp.257-261
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• 2006

Zerovalent iron (ZVI) has been recently used for environmental remediation of soils and groundwaters contaminated by chlorinated organic compounds. As a new approach to improve its reductive activity and stability, zerovalent iron-montmorillonites (ZVI-Mt) complex are synthesized by simple process. Therefore, this study was carried out to elucidate the characteristics of ZVI-Mt complex and to investigate degradation effects of fungicide chlorothalonil. The XRD patterns of ZVI-Mt complex showed distinctive peaks of ZVI and montmorillonite. In ZVI-Mt complex, the oval particles of ZVI were partly surrounded by montmorillonite layers that could prevent ZVI surface oxidation by air. The degradation ratio of chlorothalonil after 60 min exhibited 71% by ZVI and 100% by ZVI-Mt complex. ZVI-Mt21 complex exhibited much higher and faster degradation ratio of chlorothalonil compare to that of ZVI or ZVI-Mt11 complex. Also, degradation rate of chlorothalonil was increased with increasing ZVI or ZVI-Mt complex content and with decreasing initial solution pH.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.565-568
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• 1998

Amphipathic compounds (bis-sulfonate Gemini type) with double or triple long chain alkyl groups were prepared by the reaction of N-(long chain acyl)diethanolamine diglycidyl ethers with fatty alcohols, followed by the reaction with propanesultone. All these new Gemini type surfactants were soluble in water and showed much better micelle forming ability and lowering surface tension than sodium dodecyl sulfonate with one sulfonate group. cmc and ${\Upsilon}$ cmc values of the triple-chain compounds were still much smaller than those of the corresponding double-chain compounds with two common alkyl groups. The efficiency of adsorption at the water/air interface ($pC_{20}$) of these surfactants was very high. Their foaming properties, wetting ability toward a felt chip, and lime-soap dispersing requirement (LSDR) were measured. Their initial foaming properties were high but showed good low foam stability, wettability and LSDR.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.78-83
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• 2014

In this research, we evaluated the performance and characteristics of carbon supported PtM (M = Ni and Y) alloy catalysts (PtM/Cs) synthesized by a modified polyol method. With the PtM/Cs employed as a catalyst for the oxygen reduction reaction (ORR) of cathodes in proton exchange membrane fuel cells (PEMFCs), their catalytic and ORR activities and electrical performance were investigated and compared with those of commercial Pt/C. Their particle sizes, particle distributions and electrochemically active surface areas (EAS) were measured by TEM and cyclic voltammetry (CV), while their ORR activity and electrical performance were explored using linear sweeping voltammetries with rotating disk electrodes and rotating ring-disk electrodes as well as PEMFC single cell tests. TEM and CV measurements show that PtM/Cs have the compatible particle size and EAS with Pt/C. When it comes to ORR activity, PtM/C showed the equivalent or better half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production(%) to or than commerical Pt/C. Based on results gained by the three electrode tests, when the PEMFC single cell tests were carried out, the current density measured at 0.6 V and maximum power density of PEMFC single cell adopting PtM/C catalysts were better than those adopting Pt/C catalyst. It is therefore concluded that PtM/C catalysts synthesized by modified polyol can result in the equivalent or better ORR catalytic capability and PEMFC performance to or than commercial Pt/C catalyst.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.283-287
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• 2007

KIER has been developing the anode-supported flat tubular solid oxide fuel cell unit bundle for the intermediate temperature($700{\sim}800^{\circ}C$) operation. Anode-supported flat tubular cells have Ni/YSZ cermet anode support, 8 moi.% $Y_2O_3$ stabilized $ZrO_2(YSZ)$ thin electrolyte, and cathode multi-layer composed of Sr-doped $LaSrMnO_3(LSM)$, LSM-YSZ composite, and $LaSrCoFeO_3(LSCF)$. The prepared anode-supported flat tubular cell was joined with ferritic stainless steel cap by induction brazing process. Current collection for the cathode was achieved by winding Ag wire and $La_{0.6}Sr_{0.4}CoO_3(LSCo)$ paste, while current collection for the anode was achieved by using Ni wire and felt. For making stack, the prepared anode-supported flat tubular cells with effective electrode area of $90\;cm^2$ connected in series with 12 unit bundles, in which unit bundle consists of two cells connected in parallel. The performance of unit bundle in 3% humidified $H_2$ and air at $800^{\circ}C$ shows maximum power density of $0.39\;W/cm^2$ (@ 0.7V). Through these experiments, we obtained basic technology of the anode-supported flat tubular cell and established the proprietary concept of the anode-supported flat tubular cell unit bundle.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.6
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• pp.409-414
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• 2009

In 1970's Black locust(Robinia pseudoacacia) had been widely planted Korea as an important forest greening species for erosion control afforestation. Since 2000, however, the tree's leaf-yellowing symptom has often been observed at a limited region and then spreaded out over the country in 2006. This study was conducted to study soil physiochemical properties of black locust stands with and without the leaf-yellowing symptom in Osan, Gyeonggi province. Most of soils in sampling sites were mostly slightly eroded, dry, and moderately dry. Available soil depth(16cm) and total soil depth(26cm) in leaf-yellowing (LY) site were significantly lower than in non leaf-yellowing (Non-LY) site's soil depths which were 30cm and 56cm, respectively. And solid phase proportion and bulk density in soils were lower in LY site than in non-LY site soils, while soil liquid phase proportion was also low. It could reflect that LY site soils might have a lower air and moisture movement in the rhizosphere of black locust stand compared with non-LY site soils. Soil acidity in both sites was very strong acid, soil pH (4.42) of LY site was slightly lower than non-LY site's (pH 4.54). Content of available phosphorous, exchangeable $Ca^{2+}$ and $Mg^{2+}$ and percent base saturation were less than LY site. These results indicated that soil physiochemical condition in LY site, more deteriorated than non-LY site, should adversely affect the retention and supply capacity of soil nutrients and moisture. Therefore the black locust may be more sensitive to other environmental stresses.

• Journal of the Korean Chemical Society
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• v.11 no.4
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• pp.150-158
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• 1967

When anthracite burns by natural draft the mole percent of carbon monoxide (CO%) contained in exhaust gas is approximately expressed as follows in the early stage of combustion. (CO%)=$\frac{2{\alpha}}{1+{\alpha}}(CO_2%)$ exp $[-\vec{k}(No_2-Nc)^{1/2}{\tau}]$ where ${\alpha}=\frac{-0.395K_p+\sqrt{0.156K^2_p+(0.83+0.21K_p)K_p}}{0.83+0.21K_p}$ and $logK_p =-\frac{8593}{T} + 2.45logT -1.08{\times}10^{-3}T + 1.12{\times}10^{-7}T^2+2.77\vec{k},\;No_2$ and $N_c$ are the rate constant for the reaction ($CO+\frac{1}{2}O_2{\to}CO_2$), mole fraction of oxygen and oxides of carbon contained in the exhaust gas, respectively. From experimental evidence obtained in this work with natural draft combustion of briquettes the percent of carbon monoxide to the total quantity of oxides of carbon produced and rate of air flow into the furnace were: 1.76% and 0.53 l/sec (When lid is used in the furnace) 12.35% and 2.4 l/sec (without use of a lid). is the rate constant for the reaction($CO+\frac{1}{2}O_2{\to}CO_2$) and $N_0,\;and\;N_c$ are respectively the molefraction of oxygen and oxide of carbon contained in the exhaust gas.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.1-7
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• 1998

For the purpose of finding new cathode materials for medium-temperature $(700\~800^{\circ}C)$ solid oxide fuel cells, $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3,\;(x=0.0\~0.5)$ are prepared, and their thermal stability and conductivity characteristics are investigated. Also, the cathodic activities are measured after the cathode layer being attached on CGO (cerium-gadolinium oxide) electrolyte disk. The X-ray analyses indicate that the materials prepared by calcining the citrate-gels at $800^{\circ}C$ have the orthorhombic perovskite structure without discernible impurities. The thermal stability of the undoped Co perovskite is so poor that it is decomposed to the individual binary oxide even at $1300^{\circ}C$. But the partially Fe-doped cobaltates exhibit a better thermal stability to retain their structural integrity up to $1400^{\circ}C$. The observation whereby both the undoped and Fe-doped cobaltates melt at ca. $1300^{\circ}C$ leads us to perform the electrode adhesion at <$1300^{\circ}C$. The cathodic activity of $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3,\;(x=0.0\~0.5)$, electrodes is superior to $La_{0.9}Sr_{0.1}MnO_3$, among the samples of $x=0.0\~0.5$, the x=0.2 cathode shows the best activity for the oxygen reduction reaction. It is likely that the Fe-doping provides a better thermal stability to the materials but in turn imparts an inferior cathodic activity, such that the optimum trade-off is made at x=0.2 between the two factors. The total electrical conductivity and ion conductivity of $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3$, are measured to be 51 S/cm and $6.0\times10^{-4}S/cm\;at\;800^{\circ}C$, respectively. The conductivity values illustrate that the materials are a mixed conductor and the reaction sites can be expanded to the overall electrode surface, thereby providing a better cathodic activity than $La_{0.9}Sr_{0.1}MnO_3$.

• Korean Chemical Engineering Research
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• v.43 no.6
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• pp.751-755
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• 2005

Carbon dioxide, included in the flue gas from the combustion of fossil fuel, was known as a representative green house gas and various removal and utilization technologies of it has been studied for the prevention of global warming. This study was performed as an effort to find out a method to reuse carbon dioxide separated from flue gas by magnetite powder. Magnetite powder was synthesized using various oxidizers and alkalinity controlled aqueous solutions of $FeSO_4{\cdot}7H_2O$ and NaOH at 50, 80, 90, $100^{\circ}C$ and analyzed by XRD and SEM. The analysis results showed that magnetite powder synthesized at higher alkalinity and temperature had crystalline spinel and cubic structure. The reduction by hydrogen and the oxidation by carbon dioxide of synthesized powder were studied by TGA. The results showed that magnetite powder synthesized at low alkalinity and temperature was non-cubical amorphous but crystalline and cubical at high alkalinity and temperature. Comparing magnetite powders synthesized using oxidants(air and oxygen) and nitrogen, magnetite powder using more oxygen containing oxidant synthesized more crystalline magnetite powder. The experimental results of redox reaction of the synthesized magnetite powder showed that the reduction by hydrogen and the oxidation by carbon dioxide were seldom observed below $400^{\circ}C$ and observed well at $500^{\circ}C$. Magnetite powder synthesized at $100^{\circ}C$ and alkalinity(molal concentration ratio of $FeSO_4{\cdot}7H_2O$ to NaOH) of 2.0 using $O_2$ showed the highest reduction of 27.15 wt％ and oxidation of 26.73 wt％, especially at reaction temperature of $500^{\circ}C$.