• Journal of the Korean Electrochemical Society
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• v.10 no.2
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• pp.132-140
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• 2007

The phase-shift method and correlation constants for studying a linear relationship between the behavior ($-{\varphi}\;vs.\;E$) of the phase shift ($0^{\circ}{\leq}-{\varphi}{\leq}90^{\circ}$) for the optimum intermediate frequency and that (${\theta}\;vs.\;E$) of the fractional surface coverage ($1{\geq}\theta{\geq}0$) have been proposed and verified to determine the Langmuir, Frumkin, and Temkin adsorption isotherms (${\theta}\;vs.\;E$) at noble metal/aqueous electrolyte interfaces. At an Ir/0.1 M KOH aqueous electrolyte interface, the Langmuir and Temkin adsorption isotherms (${\theta}\;vs.\;E$), equilibrium constants ($K=3.3{\times}10^{-4}\;mol^{-1}$ for the Langmuir and $K=3.3{\times}10^{-3}{\exp}(-4.6{\theta})\;mol^{-1}$ for the Temkin adsorption isotherm), interaction parameter (g = 4.6 for the Temkin adsorption isotherm), and standard free energies (${\Delta}G_{ads}^0=19.9kJ\;mol^{-1}\;for\;K=3.3{\times}10^{-4}\;mol^{-1}$ and $16.5<{\Delta}G_{\theta}^0<23.3\;kJ\;mol^{-1}\;for\;K=3.3{\times}10^{-3}{\exp}(-4.6{\theta})\;mol^{-1}\;and\;0.2<\theta<0.8$) of H for the cathodic $H_2$ evolution reaction are determined using the phase-shift method and correlation constants. The inhomogeneous and lateral interaction effects on the adsorption of H are negligible. At the intermediate values of ${\theta},\;i.e,\;0.2<{\theta}<0.8$, the Temkin adsorption isotherm (${\theta}\;vs.\;E$) correlating with the Langmuir or the Frumkin adsorption isotherm (${\theta}\;vs.\;E$), and vice versa, is readily determined using the correlation constants. The phase-shift method and correlation constants are accurate and reliable techniques to determine the adsorption isotherms (${\theta}\;vs.\;E$) and related electrode kinetic and thermodynamic parameters(K, g, ${\Delta}G_{ads}^0, {\Delta}G_{\theta}^0$).

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.132-136
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• 2002

$Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(OTf)\;(OTf=CF_3SO_3^-)$ readily reacts with various amines to afford cationic amine complexes $[Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(amine)](OTf)\;(amine=NH_3,\;NHMe_2,\;NHC_4H_8,\;NH_2Ph,\;NH_2(Tol-p))$ in high yields. These complexes have been fully characterized by IR, $^1H-,\;^{19}F{^1H}-,\;and\;^{31}P{^1H}-NMR$ spectroscopy, and elemental analyses. Reaction of $Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(OTf)$ with acrylonitrile quantitatively produced the ${\pi}$-olefinic complex $Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(CH_2=CHCN)](OTf)$ which is only stable in solution in the presence of acrylonitrile. Attempt at isolating this complex in the pure solid state was failed due to partial decomposition into $Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(OTf)$ The equilibrium constants $(K_{eq}=[Pt(PCP)-(NH_2R)^+][CH_2=CHCN]/[Pt(PCP)(CH_2=CHCN)^+][NH_2R]:\;[Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(CH_2=CHCN)]^++NH_2R{\rightleftarrows}[Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(NH_2R)]^++CH_2=CHCN=Ph,\;p-tolyl)$ were calculated to be 0.28 (for R = Ph) and 3.1 (R = p-tolyl) at $21^{\circ}C$. The relative stability of the ${\sigma}$-donor amine versus the ${\pi}$-olefinic acrylonitrile complex has been found largely dependent upon the amine-basicity $(pK_b)$, implicating that acrylonitrile practically competes with amine in the platinum coordination sphere. On the contrary to the formation of the acrylonitrile complex, no reaction of $Pt(2,6-(Cy_2PCH_2)_2C_6H_3)(OTf)$ with other olefins such as ethylene, styrene and methyl acrylate was observed.

• Environmental Engineering Research
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• v.16 no.3
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• pp.165-173
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• 2011

The equilibrium and kinetic adsorption of arsenic on six different adsorbents were investigated with one synthetic and four natural types (two surface and two ground) of water. The adsorbents tested included magnetic ion exchange resins (MIEX), hydrous ion oxide particles (HIOPs), granular ferric hydroxide (GFH), activated alumina (AA), sulfur modified iron (SMI), and iron oxide-coated microsand (IOC-M), which have different physicochemical properties (shape, charge, surface area, size, and metal content). The results showed that adsorption equilibriums were achieved within a contact period of 20 min. The optimal doses of adsorbents determined for a given equilibrium concentration of $C_{eq}=10\;{\mu}g/L$ were 500 mg/L for AA and GFH, 520-1,300 mg/L for MIEX, 1,200 mg/L for HIOPs, 2,500 mg/L for SMI, and 7,500 mg/L for IOC-M at a contact time of 60 min. At these optimal doses, the rate constants of the adsorbents were 3.9, 2.6, 2.5, 1.9, 1.8, and 1.6 1/hr for HIOPs, AA, GFH, MIEX, SMI, and IOC-M, respectively. The presence of silicate significantly reduced the arsenic removal efficiency of HIOPs, AA, and GFH, presumably due to the decrease in chemical binding affinity of arsenic in the presence of silicate. Additional experiments with natural types of water showed that, with the exception of IOC-M, the adsorbents had lower adsorption capacities in ground water than with surface and deionized water, in which the adsorption capacities decreased by approximately 60-95%.

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.1047-1053
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• 2005

Cyclosporin A binding protein type-19 kDa peptidyl-prolyl cis/trans isomerase (PPIases, EC 5.2.1.8) of Euglena gracilis was purified and some of its biochemical characters were elucidated. Purification of the PPIase was achieved by employing a series of steps involving ammonium sulfate precipitation, Superdex G-75 gel filtration chromatography, Mono­Q anion and Mono-S cation exchange chromatographies, and Superdex S-200 gel filtration chromatography on FPLC. Purified PPIase had a specific activity of 8,250 units/mg, showing a 27-fold increase compared with that of cell-free extract of Euglena gracilis. The enzyme consisted of a single polypeptide chain with a molecular mass of 19 kDa. It showed high substrate specificity to succinyl-Ala-Ala-Pro-Phe-p-nitroanilide, and $k_{car}/K_{m}$, for this substrate was found to be $61.19{\times}10^5/sec$. The isomer distributions were investigated at an equilibrium of seven different peptide substrates, varying Xaa in Suc-Ala-Xaa-Pro-Phe-p-nitroanilide in dimethylsulfoxide. The cis/trans equilibrium constants were estimated to be from 0.14 (Ile) to 0.63 (Gly), which correspond to $12.00\%\;to\;38.52\%$ of the cis population, respectively, under experimental condition. The enzyme was highly sensitive to the immunosuppressive ligand cyclosporin A, but not to other immunosuppressants such as FK506 and rapamycin. Thus, it appears to belong to the class of cyclophilin.

• Applied Biological Chemistry
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• v.23 no.1
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• pp.1-6
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• 1980

The sorption characteristics of red pepper powder were analyzed in respect to its storing humidities and the types of powder product. The sorption rate of the powder was affected by the humidity values under which it was stored. At low relative humidity values below 70% RH the sorption equilibrium was easily attained, but at the higher humidity over 75% RH the equilibrium state was not reached even after a long period of storage. From the estimation of the sorption rate at arbitrary humidity an empirical equation was obtained; In ${\frac{dw}{dt}}=n\;ln(t)+ln\;c$, where w is moisture content(%) absorbed, t is time (hour) and n and c are empirical constants which were determined from empirical data. Particle sizes and drying methods of red pepper showed little effect on the sorption behavior.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.5
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• pp.531-542
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• 2011

The time-dependent temperature distribution across the section in bridges is determined on the basis of the three-dimensional finite element analyses and numerical time integration in this study. The material properties which change with time and thermal stress of concrete are taken into account to effectively trace the early-age structural responses. Since the temperature distribution is nonlinear and depends upon many material constants such as the thermal conductivity, specific heat, hydration heat of concrete, heat transfer coefficients and solar radiation, three representative influencing factors of the construction season, wind velocity and bridge pavement are considered at the parametric studies. The validity of the introduced numerical model is established by comparing the analytical predictions with results from previous analytical studies. On the basis of parametric studies for four different bridge sections, it is found that the creep deformation in concrete bridges must be considered to reach more reasonable design results and the temperature distribution proposed in the Korean bridge design specification need to be improved.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.46-53
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• 1993

The kinetic and equilibrium characteristics of copper extraction by salicylaldoxime in chloroform and benzene were investigated. Equilibrium constants such as dissociation constant, distribution coefficient of salicylaldoxime and stability constant, distribution coefficient and molar extinction coefficient of oxime-Cu chelate were determined from absorbance. Extracted species of Cu-chelate were found to be ${\bar{CuR_2}}$. Overall initial extraction rate of copper by salicylaldoxime in chloroform was expressed by the following equation : $R=k[Cu^{2+}]{\bar{[HR]}}^{0.5}/[H^+]^{0.4}$.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.2
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• pp.151-160
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• 2022

The sorption of Eu on MX-80 bentonite in Na-Ca-Cl solutions is investigated at a molal proton concentration (pH_m) range of 3 to 10 and an ionic strength (I) range of 0.1 to 6 m (mol·kgw^-1). The sorption equilibrium of Eu on MX-80 is achieved within 14 to 21 d at I = 0.1 and 6 m. The sorption distribution coefficient (K_d) values of Eu for MX-80 increase as pH_m increases from 3 to 6 for all I values, and they are independent of pH_m between 8 and 10 at I ≥ 0.5 m. Meanwhile, at I = 0.1 m, the K_d value at pH_m = 10 is slightly lower than those at pH_m = 8 and 9. The K_d values are not affected by the I values between 0.5 m and 6 m, whereas the K_d value at I = 0.1 m is greater than those at I ≥ 0.5 m, except at pH_m = 10. A two-site protolysis nonelectrostatic surface complexation and cation exchange sorption model is applied to the Eu sorption data for I ≤ 4 m, and the equilibrium constants of the sorption reactions are estimated.

• Journal of the Korean Society of Groundwater Environment
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• v.1 no.1
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• pp.23-32
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• 1994

To determine the apparent equilibrium constants, K$_{ad,app}$, for the adsorption reactions of trace metals on amorphous iron oxyhydroxide (AIO) in the Taebag coal mine area, time-adsorption and pH-adsorption experiments were performed for a selected bottom sediment mainly comprised of AIO from the study area. The results from the adsorption experiments indicate that most of the trace metals, except Pb, achieve equilibrium states with AIO and thus, the calculated K$_{ad,app}$ may represent the true apparent equilibrium constants. K$_{ad,app}$ and the stoichiometric coefficients of proton, x, of the adsorption reactions between the trace metals and AIO were respectively calculated from the intercepts and slopes of the regression lines of log($\Gamma$/ ［M］$_{aq}$)against pH provided by pH-adsorption experiments. The calculated K$_{ad,app}$ this study has the values of the range from 10$^{－4.5}$ to 10$^{2.75}$ , which is much different from the reported values by other investigators for simple experimental systems. K$_{ad,app}$ of this study is more or less close but not exactly pertinent to the estimated values for the other natural systems. It indicates that K$_{ad,app}$ for the adsorption reactions in the aquatic system in the study area is unique and thus should be determined befor the adsorption modelling. The calculated x of this study has the values of the range from -0.3 to 0.7, which is also much different from what most geochemists generally accept. The discrepancy in x may be due to the competition among different kinds of ionic species on the adsorption site or simulataneous occurrence of different kinds of adsorption reactions. The results from this study should help construct an appropriate adsorption model for the aquatic systems polluted by the coal mine drainage in the Taebag area. With the constructed model, one can describe the concentration variations of trace metals due to the adsorption in the system, which is an essential part of the investigation on the water quality affected by coal mine drainage in the Taebag coal field.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.6
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• pp.325-328
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• 2013

Phosphate has been removed in waste water by chemically synthesized graphene oxide. Removing efficiency of phosphate was investigated using phosphate dispersion aqueous solution, and 70 % of phosphate was removed in phosphate dispersion solution by chemically synthesized graphene oxide solution. Removing efficiency of phosphate was increased from 70 % to 80 % with assistant of iron nano-particle in chemically synthesized graphene oxide solution. Phosphate removing capacity was up to 89.37 mg/g at initial phosphate concentration of 100 mg/l and temperature of 303 K. The Freundlich was applied to describe the equilibrium isotherms and the isotherm constants were determined.