• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.247-252
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• 2005

The typical treatment method for fluoride polluted water is the flocculation and precipitation method which usually is capable of reducing the fluoride concentration down to the level of about 10 ppm. However, this method is no longer effective for the treatment of contaminated water having less than 10 ppm of fluorides. To remove fluorides in polluted water from the fluoride concentration between 1 to 10 ppm, several adsorbents were prepared mainly based on an activated alumina and the fluoride removal efficiencies of the adsorbents were analyzed. The best fluoride removal efficiency was obtained when the activated alumina treated by sulfuric acid was used as the adsorbent. A proper calcination temperature for the sulfuric acid contained activated alumina was found to be about $500^{\circ}C$. An adsorption isotherm for the adsorbent was also obtained by using Freundlich model. The values of the constants in Freundlich isotherm model were calculated to be K=6.63 and 1/n=0.29 based on the results obtained from the series of batch type adsorption experiments.

• Journal of the Korea Concrete Institute
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• v.29 no.4
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• pp.389-397
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• 2017

Friedel's salt is an important product of chemical adsorption between cement hydrate and chloride ions because it contains chlorine in its structure. When cement reacts with water in the presence of chloride ions, the $C_3A$ phase, and $C_4AF$ phase react with chloride to produce Friedel's salt. If chloride ions penetrate into concrete from external environments, many calcium aluminate hydrates, including AFm, can bind chloride ions. It is very important, therefore, to investigate the chloride binding isotherm of $C_3A$ phase, $C_4AF$ phase, and AFm phase to gain a better understanding of chloride binding in cementitious materials. Meanwhile, the adsorption isotherm can provide us with the fundamental information for the understanding of adsorption process. The experimental results of the isotherm can supply not only the quantitative knowledge of the cement-Friedel's salt system, but also the mechanism of adsorption and the properties of their interactions. The purpose of this study is to explore the time dependant behaviors of chloride ions adsorption with $C_3A$, $C_4AF$ and AFm phases. The chloride adsorption isotherm was depicted with Langmuir isotherm and the adsorption capacity was low in terms of the stoichiometric point of view. However, the chloride adsorption of AFm phase was depicted with Freundlich isotherm and the value was very low. Since the amount of the adsorption was governed by temperature, the affecting parameters of isotherm were expressed as a function of temperature.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1087-1094
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• 2008

This article presents a multi-scale simulation approach starting from the molecular level for the adsorption process development, specifically, in n-hexane adsorption on activated carbon. A grand canonical Monte-Carlo(GCMC) method is used for the prediction of adsorption isotherms of n-hexane on activated carbon at the molecular level. Geometric effects and hydrodynamic properties of the adsorption column are examined by means of the two dimensional CFD(computational fluid dynamics) simulation. The adsorption isotherms from the molecular simulation and the axial diffusivity from the CFD simulation are exploited for the process simulation where the elution curve of n-hexane is obtained. For the first moment(mean residence time) of the pulse-response with respect to temperature and flowrate, the process simulation results obtained from this three-steps multiscale simulation approach show a good agreement with experimental data within 20% of maximum difference. The multi-scale simulation approach addressed in this study will be useful to accelerate the adsorption process development, while reducing the number of experiments required.

• Journal of Soil and Groundwater Environment
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• v.7 no.4
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• pp.24-30
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• 2002

The laboratory adsorption batch tests were performed to investigate the adsorption characteristics of Pb on kaolinite. The characteristics such as adsorption equilibrium time, adsorption capacity, adsorption isotherm were studied, and also the effects of pH and the mixing ratio on the adsorption of Pb on kaolinite were investigated. Test results show that the adsorption equilibrium state was reached within 24 hours, and the adsorbed amount of Pb increased, but the adsorption efficiency over the initial concentration of 198 mg/l decreased, with increasing the initial concentration of Pb. And the adsorption constant, 1/n was obtained 0.9584 by Freundlich isotherm equation. Regardless of the initial concentration of Pb. the adsorbed amount of Pb as well as the adsorption efficiency were increased with increasing pH values and converged to a certain constant value above 8 of pH values. And also the adsorbed amount of Pb increased with the mixing ratio, but its efficiency increased with the mixing ratio up to 8 and then showed the decreasing tendency above that.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.388-394
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• 2018

The removal of 2,4-dichlorophenol (2,4-dichlorophenol, 2,4-DCP) in aqueous solution was studied using the magnetic activated carbon (MAC) prepared from waste citrus peel. The adsorption characteristics of 2,4-DCP by MAC were investigated by varying the contact time, MAC dose, solution temperature, pH and 2,4-DCP concentration. The isothermal adsorption data were well explained by the Langmuir isotherm model equation and the maximum adsorption capacity calculated from the Langmuir isotherm equation was 312.5 mg/g. The adsorption kinetic data were well described by the pseudo-second-order reaction equation. The intraparticle diffusion model data indicated that both the film and intraparticle diffusion occur simultaneously during the adsorption process. The thermodynamic parameters of ${\Delta}H^o$ and ${\Delta}G^o$ have positive and negative values, respectively, indicating that the adsorption of 2,4-DCP by MAC is a spontaneous endothermic reaction. After the adsorption experiment was completed, the used MAC could be easily separated by an external magnet.

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

• KSBB Journal
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• v.20 no.3
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• pp.244-249
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• 2005

Chiral separation of racemic ibuprofen was achieved on a Kromasil KR100-5CHI-TBB column. Some chromatographic parameters (resolution, number of theoretical plates, HETP, capacity factor) are calculated under different separation conditions such as change of mobile phase compositions (hexane / t-BME : 85 / 15, 75 / 15, 65 / 35, 55 /45) as well as acetic acid concentrations for adjusting pH (0.1 to 1 $v/v\%$). Flow rate versus number of theoretical plates and HETP were compared to evaluate column efficiency. To determine the adsorption isotherms, PIM (Pulsed Input Method) was carried out. At concentrations of racemic ibuprofen between 0.1 and 0.3 mg/ml, S- and R-ibuprofen have the same retention time of 4.48 and 5.81 min. Ibuprofen isotherms show a linear form under concentrations of 0.3 mg/ml with eluent (hexane / t-BME = 55 / 45).

• Resources Recycling
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• v.25 no.4
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• pp.60-67
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• 2016

This study was conducted to establish the adsorption-desorption mechanism and the optimum condition of chromatographic operation for separations of heavy rare earth elements (Gd, Tb, Dy) using a p507-containing resin. By employing Langmuir and Freundlich isotherm together with pseudo first and second order kinetics, absorption-desorption reaction mechanism was investigated. Langmuir and Freundlich isotherm was applied under assumption that adsorption reaction occurs in form of monolayer, and because the result was identical to the assumption, now we know adsorption of heavy rare earth elements occurs in form of monolayer. Concerning the pseudo first and second order kinetic, the pseudo second order seemed to be more suitable to represent heavy rare earth element adsorption mechanism. By using the extraction chromatography to separate heavy rare earth elements, ${\alpha}^{Tb}_{Gd}=1.24$, and ${\alpha}^{Dy}_{Tb}=1.03$ were confirmed in eluent HCl 0.25 M which indicates almost perfect separations of three elements. Furthermore, as concentrations of eluent became higher, the resolution value decreased and the elution area got shortened.

• Clean Technology
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• v.18 no.3
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• pp.312-319
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• 2012

Malachite green is used a dye but malachite green is harmful toxic substance. In this study, the adsorption characteristics of zeolite has been investigated for the adsorption of malachite green dissolved in water. The effects of initial dye concentration, contact time, pH and temperature on adsorption of malachite green by a fixed amount of zeolite have been studied in batch adsorber and fixed bed. The adsorption equilibrium data are successfully fitted to the Freundlich isotherm equation in the temperature range from 25 to $45^{\circ}C$. The estimated values of k and ${\beta}$ are 23.60-46.88, 0.225-0.347, respectively. The mechanism of the adsorption process was determined from the intraparticle diffusion model. The effects of the operation conditions of the fixed bed on the breakthrough curve were investigated. When the inlet concentration and initial flow rate of malachite green are increased, the corresponding adsorption breaktime appears to decrease. Breaktime increased with increasing bed height and length of adsorption zone showed similar patterns.

• KSBB Journal
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• v.11 no.2
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• pp.173-180
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• 1996

The contamination of the environment by heavy metals results in a serious public health problem due to the toxicity of those pollutants even at low concentrations. Microorganisms may be used to remediate wastewaters contamlialtd with heavy metals. The waste S. cerevisiae is an inexpensive readily available source of biomass for bioremediation of wastewater. S. cerevisiae was investigated for their ability to absorb Pb. The crushed biomass of S. cerevisiae exhibited higher Pb uptake capacity than the living S. cerevisiae and the sterilized S. cerevisiae. At the same metal concentration, metal uptake per unit concentration or adsorbent decreased when the biomass concentration rises. The order of the biosorption capacity of the living S. cerevisiae was Pb>Cu>Cd=Co>Cr. When S. cerevisiae was pretreated with 0.1 M NaOH, Pb uptake was increased by 150 percent and 0.1 M HC1, 0.1 M $H_2S_O4$ solutions were efficient in the desorption of Pb. The sorption equilibrium of Pb ions can be described by the Freundlich and Langmuir models.