• 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, ${\Delta}G_{ads}^0, {\Delta}G_{\theta}^0$).

• Journal of Environmental Science International
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• v.5 no.2
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• pp.243-252
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• 1996

In order to investigate the effects of pH and organic matter content on cadmium adsorption and exchangeable cations desorption in soils, the adsorption isotherms of cadmium and the desorption isotherms of calcium and magnesium on four New jersey soils at four pH values were plotted, and the cadmium partition coefficients (Kd) were also calculated. The slopes of cadmium adsorption isotherms dramatically increased with increasing solution pH. Judging from Langmuir adsorption equations, the maximum adsorption quantities(b) of cadmium at high pH values were much greater than those at low pH values for the same soil. The partition coefficients increased greatly with increasing solution pH. The slopes of regression equations between partition coefficients and pH values were steep in the order of the organic matter content of the soils. The correlation coefficients (r2) between partition coefficient and organic matter content for soils. The correlation coefficients (r2) between partition coefficient and organic matter content for $1\times10^{-4}$M increased from 0.3027 at pH 4.0 to 0.9964 at pH 8.5 and from 0.2093 at pH4.0 at 0.9657 at pH 8.5 for$2\times10^{-4}$M ${Cd(NO_3)}_2$. The desorption quantities of calcium and magnesium decreased with increasing solution pH and increased with- increasing cadmium adsorption.

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.531-538
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• 2004

Studies of adsorption isotherms with sharp step-wise layer condensation help us to better understanding of two dimensional layers. For this, an adsorption isotherm apparatus, using a phase modulated ellipsometric technique, has been constructed and an adsorption experiment has been performed. With subatomic scale resolution(∼0.3 $\AA$), the adsorption processes could be observed by ellipsometric signals. On measurement of multilayer adsorption of argon on highly oriented pyrolytic graphite(HOPG), thousands of adsorbed layers were observed at 34.04 K, which suggests that the adsorption is completely wet. On the contrary nine sharp layers of steps for adsorptions and desorptions were observed at 67.05 K. These isotherms obtained can provide a lot of information about thermodynamic states, bonding energies between adsobate and substrate, and structure transitions in the adsorbed film.

• Environmental Engineering Research
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• v.13 no.2
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• pp.79-84
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• 2008

Adsorption of heavy metals by sawdust was investigated to evaluate the effectiveness of using sawdust to remove heavy metals from aqueous solutions. Kinetic and isotherm studies were carried out by considering the effects of initial concentration and pH. The adsorption isotherms of heavy metals fitted the Langmuir or Freundlich model reasonably well. The adsorption capacity of metal was in the order $Pb^{2+}$ > $Cu^{2+}$ > $Zn^{2+}$. A high concentration of co-existing ions such as $Ca^{2+}$ and $Mg^{2+}$ depressed the adsorption of heavy metal. Adsorption data showed that metal adsorption on sawdust follows a pseudo-second-order reaction. Kinetic studies also indicated that both surface adsorption and intraparticle diffusion were involved in metal adsorption on sawdust. Column studies prove that sawdust could be effective biosorbent for the removal of heavy metals from aqueous phase.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.3
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• pp.389-395
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• 2006

The use of pine bark, a natural adsorbent prepared from Korean Red Pine (Pinus densifloral), was studied for its adsorption behavior of lead ion from aqueous solution. Adsorption experiments were carried out on lead ion concentrations of 10mg/L. Adsorption of lead ion could be described by both Langmuir and Freundlich adsorption isotherms. Treatment of the bark with nitric acid greatly increased initial adsorption rate, and equilibrium sorption capacity increased by approximately 48%. A pseudo second-order kinetic model fitted well for the kinetic behavior of lead ion adsorption onto the bark. Acid-treated bark demonstrated its adsorption capacity quite close to that of granular activated carbon. Results of this study indicated that ion exchange and chelation were involved in the adsorption process.

• Journal of Environmental Science International
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• v.12 no.9
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• pp.1011-1016
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• 2003

Adsorption of phosphate, sulfate, and copper ion to goethite was investigated. Goethite was prepared in the alkaline solution. In the single adsorbate systems, the final equilibrium plateau reached within 20 min. The adsorption isotherms of the individual ions could be well described by the Langmuir equation. The maximum adsorption capacities (q$\_$max/) were calculated as 0.483 m㏖/g and 0.239 m㏖/g at pH 3 for phosphate and sulfate ion, and 0.117 m㏖/g at pH 6 for copper ion, respectively, In competitive adsorption system with phosphate and sulfate, phosphate ion was a stronger competitor for adsorption on goethite than sulfate ion, which was consistent with higher affinity of phosphate ion for the surface compared to sulfate ion. The existence of sulfate ion enhanced the adsorption of copper ion but the adsorption of sulfate was inhibited when copper ion was present.

• Journal of the Korean Society of Clothing and Textiles
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• v.14 no.1 s.33
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• pp.13-19
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• 1990

The water-vapor sorption isotherms of viscose rayon and of modified viscose rayon were studied to elucidate the change of sorptivity by the DMDHEU resin finish. To determine the sorption isotherms, moisture regains of the samples were measured at various humidities. The sorption isotherms were determined by the BET and GAB multilayer adsorption theories. The adsorption isotherm of the starting rayon was Brunauer Type II while with increasing resin content those of the DMDHEU-treated rayon became progressively more like Type IV. The DMDHEU-treated samples appeared to be hydrophilic due to the hydrophilicity of DMDHEU although moisture regains at higher humidities markedly decreased because of an impediment in swelling by crosslinkings. The $W_{m}$ value and surface area of crosslinked samples increased with increasing resin content. VR-R-6 which was the most heavily crosslinked viscose rayon had the highest $W_{m}$ and surface area values among all the samples. Relative sorption hysteresis was decreased as humidity increased for all samples. The untreated viscose rayon appeared to have a higher value than the DMDHEU-treated rayon.

• Food Science of Animal Resources
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• v.18 no.4
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• pp.285-291
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• 1998

Adsorption isotherms of water vapour for infant formula milk powders manufactured by P. M. and N company in Korea were measured at temperatures between 20, 30 and 40$^{\circ}C$ using COST-90 modified method. Results showed that the isotherms were sigmoidal in shape. The adsorption isotherms of milk powder were depending on the temperature and products. The BET-model were applied and analyzed to compare the experimental value. It was found that the BET-model is fitted with measuring data. Sample P showed the lowest monolayer value and sample N showed the highest. Isosteric heat obtained upon application of BET-model was calculated in this field of temperature using the Clausius-Clapeyron equation. It is suggested that the usage of the BET-model to estimate the heat of water sorption in infant formula milk powder should be in agreement with the results from COST-90 project.

• Journal of the Korean Chemical Society
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• v.15 no.5
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• pp.265-274
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• 1971

A significant structure theory of monolayer physical adsorption is developed. The theory is tested with the adsorptions on graphite of gases Ar, $N_2$, $CHCl_3$, and $CCl_4$. A restricted rotation model is used for the polyatomic molecules $N_2$, $CHCl_3$, and $CCl_4$. The computed isotherms and heats of adsorption are in good agreement with experiment in all cases studied.

• Applied Chemistry for Engineering
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• v.17 no.3
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• pp.280-285
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• 2006

Adsorption characteristics of $H_{2}S$ on KOH impregnated activated carbon were evaluated using dynamic adsorption method in a fixed bed. The pore properties, including BET's specific surface area, pore volume, pore size distribution, and mean pore diameter of these KOH impregnated activated carbons, were characterized from $N_{2}$ adsorption/desorption isotherms. Adsorption equilibrium data were correlated with Langmuir and Freundlich isotherms. The adsorption of $H_{2}S$ onto the KOH impregnated activated carbon is better fitted by the Langmuir isotherm. An increase in the content of oxygen affects the performance of KOH impregnated activated carbon to the greatest extent.