• Journal of the Korean Chemical Society
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• v.37 no.11
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• pp.951-960
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• 1993

$Hg^{2+}$-induced aquation trans-[Co(3,2,3-tet)$X_2]^+$(3,2,3-tet = 4,7-diazadecane-1,10-diamine, $X_2\;=\;Cl_2,\;(NO_2)Cl,\;Br_2,\;(NO_2)Br,\;(NO_3)_2)$ complexes was investigated in aqueous solution. The products and the reaction mechanism were confirmed by chromatography, UV/Vis. spectrum, and circular dichroism (CD) spectrum. From the results, $Hg^{2+}$-induced aquation of 3,2,3-tet system has been produced cis-${\beta}$ complex via trans complex. The kinetic studies on $Hg^{2+}$-induced aquation of trans-[Co(3,2,3-tet)$Cl_2]^+$ complex and trans-[Co(3,2,3-tet)$(NO_2)Cl]^+$ complex were also carried out to study the reaction mechanism. The results show that trans-[Co(3,2,3-tet)$Cl_2]^+$ complex undergoes the D(dissociative)-mechanism and trans-[Co(3,2,3-tet)$(NO_2)Cl]^+$ complex $I_d$(interchange dissociavite)-mechanism. In order to confirm steric course for the reaction mechanism, $Hg^{2+}$-induced aquation on trans-[Co(R,R-3,2,3-tet)$Cl_2]^+$ complex to which chiral R,R-3,2,3-tet was coordinated instead of the racemic(R,R:S,S) 3,2,3-tet was used has been examined by CD spectrum. From the results, the final complex was confirmed to be ${\Delta}-cis-{\beta}$-[Co(R,R-3,2,3-tet)$(OH_2)_2]^{3+}$ complex indicating the chirality was retained through whole process.

• Journal of the Mineralogical Society of Korea
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• v.28 no.3
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• pp.255-263
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• 2015

To investigate the effect of the weathering process of biotite on Cs sorption, sorption experiment of Cs with $10^{-3}M$ solution was carried out on the biotite reacted at different reaction times at pH 2 and 4, and 1 M solutions of Na, K, Ca, Mg, Rb, and Cs. Peak changes were observed for some samples by XRD, indicating that new mineral phase formed by biotite weathering. Among several factors, cations in solutions have the most significant influence on the mineralogical changes. The samples reacted with Na showed the most outstanding change with increasing peak width and appearance of $12{\AA}$ peak and $14{\AA}$ peak. This new peaks indicate the formation of hydrobiotite and vermiculite. The new peaks had stronger peak intensity for the sample reacted at pH 4 than that at pH 2, probably due to the fast dissolution of small particles and edges and resultant decrease in the formation of expandable layers. The biotite reacted at Mg solution showed small intensity at $14{\AA}$. Based on XRD results, the degree of biotite weathering was in the order of Na, Mg, and Ca. The samples reacted with K, Rb, Cs solutions did not show noticeable mineralogical changes caused by weathering. The amount of sorbed Cs on weathered biotite showed close relationship with the degree of weathering indicated by XRD. At both pH 2 and 4, the biotite reacted with Na solution showed the highest Cs sorption, and those with Mg and Ca solutions showed the next highest ones. The sorbed amounts of Cs on the bitote reacted with K, Rb, Cs solutions were relatively low. This indicates that at the Cs concentration ($10^{-3}M$) which we used for this experiment and which was much higher than the maximum Cs concentration sorbed on the frayed edge site, expandable layer plays more important role than frayed edge. In the cases of K, Rb, and Cs solutions, Cs sorption was decreased because K is the same cations as the one in the interlayer or the sorption of Rb and Cs on the frayed edge prevents the formation of expandable layers.

• 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 $500^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.273-280
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• 1989

The spectra of the $Co^{II}CyDTA$(CyDTA: cyclohexyldiaminetetraacetic acid) complex have been measured in aqueous solution of pH = 6-13.2. The red shift of the spectrum in the more basic solution was ascribed to the transformation of $CoCyDTA^{2-}$ into $CoCyDTA(OH)^{3-}$. The equilibrium constant, $K_{OH} = [CoCyDTA(OH)^{3-}]/[CoCyDTA^{2-}][OH^-]$ was $75M^{-1}$ at $40^{\circ}C$. The electron transfer reactions of $CoCyDTA^{2-}$ and $CoCyDTA(OH)^{3-}$ with $Fe(CN)_6^{3-}$ have been studied using spectrophotometric technique in the range of pH applied to the determination of equilibrium constant. The pseudo first-order rate constants observed ($k_{obs}$) were not changed upto pH = 10.8, but increased with increasing pH in the range of pH = $10.8{\sim}13.0$. The rate law reduced in the range of pH = 6-13 was $k_{obs} = (k_3[CoCyDTA^{2-}] + k_4[CoCyDTA(OH)^{3-}])/(1+K_1[CoCyDTA^{2-}])$. The rate constants of the reactions (3a) and (3b), $k_3$ and $k_4$ respectively have been determined to be 0.529 and $4.500M^{-1}sec^{-1}$ at $40^{\circ}C$. The activation entropies (147{\pm}1.1JK^{-1} mol^{-1}$ at pH = 10.8) and activation volumes $(6.25cm^3mol^{-1}, pH = 10.8)$ increased with increasing pH, while the activation enthalpy (12.44 ${\pm}$ 0.20 kcal/mole) was independent of pH. Using the pH effect on the rate constants, the activation entropies and the activation volumes, the mechanism of the electron transfer reaction for $Co^{II}-Fe^{III}$ system was discussed.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.330-337
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• 2011

In this research, the preparation processes for making a series of $\omega$-mercapto alkylamine 1 and $\omega$-mercapto alkanoic acid 2 useful for studying of the self-assembled monolayer(SAM) are described. The preparation methods of the first goal materials, $\omega$-mercapto alkylamines 1 were carried out as follows: First, $\omega$-phthalimide alkanol 3 was synthesized from commercially available potassium phthalimide derivatives and $\omega$-bromoalkanol in DMF at $80{^{\circ}C}$ via substitution reaction. After refluxing $\omega$-phthalimide alkanol 3 with hydrazine hydrate in ethanol followed by treating with c-HCl, $\omega$-aminoalkanol 4 was obtained in 76-98% yield, accompanied with side-product 5. Bromination of hydroxyl moiety of $\omega$-aminoalkanol 4 using aqueous hydrobromic acid furnished $\omega$-bromoamine 6 in 34-97% yields. Substitution reaction 6 with thiourea in 95% ethanol gave $\omega$-aminoalkanthiuronium 7, which was treated with aqueous strong base and aqueous strong sulfuric acid gave desired products, $\omega$-mercapto alkylamines 1 through overall 5 steps. The second target material, $\omega$-mercapto alkanoic acid 2 was prepared via 2 steps. $\omega$-bromo alkanoic acid was reacted with thiourea to give $\omega$-thiourea alkanoic acid 7 in 69-85%, which was treated with aqueous strong base and strong acid to furnish $\omega$-mercapto alkanoic acid 2 in 50-98%. The fabricated long-chain alkylthiol(LCAT) can be used as linkers to immobilize protein, enzyme and various kinds of biomolecules on the surface of metallic materials(Au, Pt, Ti) by SAM, and can be useful chemical tools for the application study on the surface modification of metallic materials.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.485-494
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• 2000

According to the worldwide interest in controlling $CO_2$ which contributes to green house effect. new techniques of reducing $CO_2$ are under development. We have developed new technique for reducing $CO_2$. In low $CO_2$ concentration. the chemical absorption method is useful. In this study. the kinetics of the reaction between $CO_2$ and the sterically hindered amine solution with piperazine. have been investigated from measurements of the rate of absorption of $CO_2$ in the stirred vessel that has a horizontal liquid-gas interface, in the temperature range $30{\sim}70^{\circ}C$. The experiments were carried out in the range 10.130~20.260 kPa of partial pressure of $CO_2$, and in aqueous $2.0kmol/m^3$ AMP solution with $0{\sim}0.4kmol/m^3$ piperazine The experimental results are as follows: 1) The absorption rate of $CO_2$ into aqueous AMP + piperazine solution is gett ng faster than that of aqueous AMP absorbents with temperature. Because the activation energy of piperazine 57.147 kJ/mol is higher than that of AMP 41.7kJ/mol. therefore the effect of piperazine on absorption rate increases with temperature. 2) Compared with aqueous AMP solution. the absorption rate of $CO_2$ into AMP + piperazine solution increases from 6.33% at $30^{\circ}C$ to 12% at $70^{\circ}C$, so AMP + piperazine solution is thought to be a better than AMP solution, 3) The reaction rate constants of piprazine in aqueous AMP solution with $CO_2$ have been determined as 217.21, 420.46, 707.00 and $3162.167m^3/kmol{\cdot}s$ respectively at 30, 40, 50 and $70^{\circ}C$ but these results are higher than those of Xu which were 186.7. 367.32. 693.01. $2207.65m^3/kmol{\cdot}s$ at 30, 40, 55, $70^{\circ}C$in aqueous MDEA solution. So the regression analysis of the data has led to the following equation In $k_p$ =28.324-6934.7/T.

• Clean Technology
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• v.25 no.1
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• pp.81-90
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• 2019

A dielectric barrier discharge (DBD) plasma reactor packed with $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst was used for the dry ($CO_2$) reforming of propane (DRP) to improve the production of syngas (a mixture of $H_2$ and CO) and the catalyst stability. The plasma-catalytic DRP was carried out with either thermally or plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst at a $C_3H_8/CO_2$ ratio of 1/3 and a total feed gas flow rate of $300mL\;min^{-1}$. The catalytic activities associated with the DRP were evaluated in the range of $500{\sim}600^{\circ}C$. Following the calcination in ambient air, the ${\gamma}-Al_2O_3$ impregnated with the precursor solution ($Ni(NO_3)_2$ and $Ce(NO_3)_2$) was subjected to reduction in an $H_2/Ar$ atmosphere to prepare $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst. The characteristics of the catalysts were examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrometry (EDS), temperature programmed reduction ($H_2-TPR$), temperature programmed desorption ($H_2-TPD$, $CO_2-TPD$), temperature programmed oxidation (TPO), and Raman spectroscopy. The investigation revealed that the plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst exhibited superior catalytic activity for the production of syngas, compared to the thermally reduced catalyst. Besides, the plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst was found to show long-term catalytic stability with respect to coke resistance that is main concern regarding the DRP process.

• Economic and Environmental Geology
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• v.53 no.6
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• pp.667-675
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• 2020

An Alum-sludge based adsorbent (ASBA) was synthesized by the hydrothermal treatment of alum sludge obtained from settling basin in water treatment plant. ASBA was applied to remove fluoride and arsenic in artificially-contaminated aqueous solutions and mine drainage. The mineralogical crystal structure, composition, and specific surface area of ASBA were identified. The result revealed that ASBA has irregular pores and a specific surface area of 87.25 ㎡ g-1 on its surface, which is advantageous for quick and facile adsorption. The main mineral components of the adsorbent were found to be quartz(SiO2), montmorillonite((Al,Mg)2Si4O10(OH)2·4H2O) and albite(NaAlSi3O8). The effects of pH, reaction time, initial concentration, and temperature on removal of fluoride and arsenic were examined. The results of the experiments showed that, the adsorbed amount of fluoride and arsenic gradually decreased with increasing pH. Based on the results of kinetic and isotherm experiments, the maximum adsorption capacity of fluoride and arsenic were 7.6 and 5.6 mg g-1, respectively. Developed models of fluoride and arsenic were suitable for the Langmuir and Freundlich models. Moreover, As for fluoride and arsenic, the increase rate of adsorption concentration decreased after 8 and 12 hr, respectively, after the start of the reaction. Also, the thermodynamic data showed that the amount of fluoride and arsenic adsorbed onto ASBA increased with increasing temperature from 25℃ to 35℃, indicating that the adsorption was endothermic and non-spontaneous reaction. As a result of regeneration experiments, ASBA can be regenerated by 1N of NaOH. In the actual mine drainage experiment, it was found that it has relatively high removal rates of 77% and 69%. The experimental results show ASBA is effective as an adsorbent for removal fluoride and arsenic from mine drainage, which has a small flow rate and acid/neutral pH environment.

• Food Science and Industry
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• v.53 no.1
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• pp.2-32
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• 2020

In recent years, significant importance has been given to chitooligosaccharides (COS) due to its potent notable biological applications. COS can be derived from chitosan which is commonly produced by partially hydrolyzed products from crustacean shells. In order to produce COS, there are several approaches including chemical and enzymatic methods which are the two most common choices. In this regard, several new methods were intended to be promoted which use the enzymatic hydrolysis with a lower cost and desired properties. Hence, the dual reactor system has gained more attention than other newly developed technologies. Enzymatic hydrolysis derived COS possesses important biological activities such as anticancer, antioxidant, anti-hypersentive, anti-dementia (Altzheimer's disease), anti-diabeties, anti-allergy, anti-inflammatory, etc. Results strongly suggest that properties of COS can be potential materials for nutraceutical, pharmaceutical, and cosmeceutical product development.

• Microbiology and Biotechnology Letters
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• v.26 no.2
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• pp.102-109
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• 1998

To investigate the increased acid tolerance of a acid-resistant mutant Leuconostoc mesenteroides M-100 improved as a kimchi starter, proton permeability, ATPase acitivity, glycolysis activity, $Mg^{2+}$ releasement, and membrane fatty acid composition were studied and comprised with its wild type Leuconostoc mesenteroides Mw. In the proton permeability experiment, the mininum values of the average half time ($t_{1/2}$) of pH equilibration through the cell membrane of the Mw and the M-100 were about 8.6 min and 9.2 min in 150 mM KCI solution, respectivily. In the 3% NaCl solution, the $t_{1/2}$ values of the Mw and the M-100 were 6min and 8.6 min, respectivily. The values and pHs of maximal specific activities of ATPase originated from the Mw and the M-100 were 0.6U at pH 5.5 and 0.8U at pH 5.5, respectivily. The result of pH dependence of glycolysis showed that the M-100 had higher activities than that of Mw except at pH 5.0. The releases of magnesium from the Mw and the M-100 were observed about 36.5% and 13% at pH 4.0 after 2 hours, respectivily. The results of comparison of membrane fatty acid composition of the Mw with the M-100 showed that $C_{12}$, $C_{14}$, $C_{18:1}$, and $C_{19:0cyclo}$ were major different fatty acids between two strains and the content of $C_{18:1}$, and $C_{19:0cyclo}$ were 23.4%, 10.2% in the Mw and 15.1%, 12.2% in the M-100. These results indicated that acid tolerance of the M-100 was significantly improved in comparison with its wild type Mw.