• Polymer(Korea)
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• v.36 no.3
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• pp.338-343
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• 2012

Interfacial properties of commercially available soft contact lens hydrogels were studied to understand thermodynamic phenomena of protein adsorption. Hydrogel particles ($1{\times}1mm^2$) with varying water wettability were exposed to bovine serum albumin solutions for an hour. The remained albumin solutions were analyzed with Bradford assay method. The amount of protein adsorbed to hydrogels increased with protein solution concentrations following Langmuir isotherm. The partition coefficient ($P$) and Gibbs free energy cost of dehydrating the surface region by protein displacement upon adsorption increased with increasing hydrophilicity of contact lens. Understanding of physical chemistry in protein adsorption to contact lens materials enabled elucidating relationships between surface energy and albumin adsorption capacity.

• Journal of Environmental Science International
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• v.9 no.2
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• pp.145-149
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• 2000

The purpose of this study was to determine whether Vermi Cast could be used effectively to remove $SO_2$ from flue gas, and then to investigate optimum adsorption conditions. The Vermi Cast used as adsorbent was mechanically screened with 8~20 mesh sieve. The adsorption data for $SO_2$ were regressed using the Freundlich isotherm. The fit was generally satisfactory ($R^2$=0.945~0.982). With the temperature changes from 2$0^{\circ}C$ to 4$0^{\circ}C$, the constant k in Freundlich isotherm qe= $kCe^{1/n}$, decreased from 1.409 at 2$0^{\circ}C$to 0.297 at 4$0^{\circ}C$, and the exponent 1/n were decreased from 0.343 to 0.134. With the bed depth changes from 10cm to 30cm, the adsorption capacity expressed as mmol of $SO_2$ adsorbed per g of Vermi Cast increased from 0.247 to 0.381. Moisture content is an important parameter in the $SO_2$ adsorbed were observed over 0.3mmol $SO_2$ /g Vermi Cast. The best adsorption capacity was 0.487mmol $SO_2$ /g Vermi Cast, and it was obtained with moisture content 37%, temperature 2$0^{\circ}C$. From the above results, ti might be concluded that Vermi Cast is effectively as a good adsorbent to remove $SO_2$ from flue gas.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.943-950
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• 2009

Cadmium (Cd) adsorption onto the activated carbon containing hydroxyapatite (HAP) was investigated in batch experiments and response surface methodology (RSM) using the Box-Behnken methods were applied to the experimental results. Cd adsorption with different HAP mass ratio of from 10% to 30%. With more HAP, Cd was more adsorbed. These results suggest that the higher HAP mass causes an increase of the ion exchange potential of the HAP sorbent. Equilibrium experimental results from Cd adsorption was fitted to Langmuir and Freundlich isotherm models. Cd adsorption on HAP sorbent were found to follow the Freundlich isotherm model well in the initial adsorbate concentration range. Also, Cd adsorption was a function of the HAP mass ratio ($x_1$), initial Cd concentration ($x_2$), and initial pH ($x_3$) from the application of the RSM. Statistical results showed the order of significance of the independent variables to be initial Cd concentration > HAP mass ratio > initial pH.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.164-171
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• 2020

Adsorption characteristics of reactive red 120 (RR 120) dye by a coal-based granular activated carbon (CGAC) from an aqueous solution were investigated using the amount of activated carbon, pH, initial concentration, contact time and temperature as adsorption variables. Isotherm equilibrium relationship showed that Langmuir's equation fits better than that of Freundlich's equation. The adsorption mechanism was considered to be superior to the adsorption of monolayer with uniform energy distribution. From the evaluated Langmuir separation coefficients (R_L = 0.181~0.644), it was found that this adsorption process belongs to an effective treatment area (R_L = 0~1). The adsorption energy determined by Temkin's equation and Dubinin-Radushkevich's equation was E = 15.31~7.12 J/mol and B = 0.223~0.365 kJ/mol, respectively. The adsorption process showed the physical adsorption (E < 20 J/mol and B < 8 kJ/mol). The adsorption kinetics followed the pseudo first order model. The adsorption reaction of RR 120 dye on CGAC was found to increase spontaneously with increasing the temperature because the free energy change decreased with increasing the temperature. The enthalpy change (12.747 kJ/mol) indicated an endothermic reaction. The isosteric heat of adsorption (△H_x = 9.78~24.21 kJ/mol) for the adsorption reaction of RR 120 by CGAC was revealed to be the physical adsorption (△H_x < 80 kJ/mol).

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.679-686
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• 2019

Characteristics of adsorption equilibrium, kinetic and thermodynamic of aniline blue onto activated carbon from aqueous solution were investigated as function of initial concentration, contact time and temperature. Adsorption isotherm of aniline blue was analyzed by Langmuir, Freundlich, Redlich-Peterson, Temkin and Dubinin-Radushkevich models. Langmuir isotherm model fit better with isothermal data than other isotherm models. Estmated Langmuir separation factors ($R_L=0.036{\sim}0.068$) indicated that adsorption process of aniline blue by activated carbon could be an effective treatment method. Adsorption kinetic data were fitted to pseudo first order model, pseudo second order model and intraparticle diffusion models. The kinetic results showed that the adsorption of aniline blue onto activated carbon well followed pseudo second-order model. Adsorption mechanism was evaluated in two steps, film diffusion and intraparticle diffusion, by intraparticle diffusion model. Thermodynamic parameters such as Gibbs free energy, enthalpy and entropy for adsorption process were estimated. Enthalpy change (48.49 kJ/mol) indicated that this adsorption process was physical adsorption and endothermic. Since Gibbs free energy decreased with increasing temperature, the adsorption reaction became more spontaneously with increasing temperature. The isosteric heat of adsorption indicated that there is interaction between the adsorbent and the adsorbate because the energy heterogeneity of the adsorbent surface.

• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.25-30
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• 2000

The relation between the phase-shift profile for the intermediate frequencies and the Langmuir adsorption isotherm at the poly-$Pt/0.1\;M\;H_2SO_4$ aqueous electrolyte interface has been studied using ac impedance measurements, i.e., the phase-shift methods. The suggested interfacial equivalent circuit consists of the serial connection of the electrolyte resistance ($R_S$), the faradaic resistance $(R_F)$ and the equivalent circuit element $(C_P)$ of the adsorption pseudocapacitance $(C_\varphi)$. The delayed phase shift $(\varphi)$ depends on both the cathode potential (E) and frequency (f), and is given by $\varphi=-tan^{-1}[1/2{\pi}f(R_s+R_F)C_p]$. The phase-shift profile $(\varphi\;vs.\;E)$ for the intermediate frequency (ca. 6Hz) can be used as an experimental method to determine the Langmuir adsorption isotherm (9 vs. E). The equilibrium constant (K) for H adsorption and the standard free energy $({\Delta}G_{ads})$ of H adsorption at the poly-$Pt/0.1\;M\;H_2SO_4$ electrolyte interface are $1.8\times10^{-4}\;and\;21.4kJ/mol$, respectively. The H adsorption is attributed to the over-potentially deposited hydrogen (OPD H).

• Journal of the Korean Society of Clothing and Textiles
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• v.23 no.4
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• pp.510-516
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• 1999

Dyeing properties of cotton fabrics with green tea colorants were studied by investigating the effects of dyeing conditions such as colorants concentration. pH dyeing temperature and time on dye uptakes effects of mordats on dye uptakes and color change and effects of cationizing agent on dye uptakes. And various colorfastnesses of dyed fabrics were evaluated for practical use. Green tea colorants showed low affinity to cotton and produced yellowish red color. Freundlich adsorption isotherm was obtained thus it is considered that hydrogen bondings are formed between colorants and cotton. Dye uptake was maximum at pH 5 and decreased as pH increased. Mordants especially Cu and Sn were effective for increasing dye uptake. Dye uptakes were improved remarkably by cationizing. Cationized cotton showed Langumuir adsorption isotherm indicating that ionic bondings were formed between colorants and cationized cotton. While mordanting did not affect lightfastness cationizing affected adversely. Colorfastness of cationized sample was generally inferior to that of mordanted samples.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.406-414
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• 2010

A novel polyacrylamide grafted hydrous ferric oxide adsorbent composite has been synthesized by using glow discharge electrolysis plasma. To optimize the synthesis conditions, the following parameters were examined in detail: applied power, discharge time, post polymerization temperature, post polymerization time, amount of crosslinking agent and hydrous ferric oxide gel added and so on. The adsorbent was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The removal percentage of the adsorbent in Pb(II) solution was examined and the data obtained showed that the adsorbent composite has a high capacity for lead ion. For the use in wastewater treatment, the thermodynamic and kinetic of Pb(II)-capture were also studied. Results indicated that the adsorption reaction was a spontaneous and an endothermic process, and it seems to be obeyed a pseudo-secondorder rate model. Moreover, the adsorption isotherm of Pb(II)-capture is following the Langmuir and Freundlich isotherm models.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.301-306
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• 2020

We investigated the individual biosorption removal of lead, copper, and nickel ions from aqueous solutions using Chara sp. algae powder in a batch mode. The impact of several parameters, such as initial concentration of the metal ions, contacting time, sorbent dose, and pH on the removal efficiency, was investigated. The maximum removal efficiency at optimum conditions was found to be 98% for Pb(II) at pH = 4, 90% for Cu(II) at pH = 5, and 80% for Ni(II) at pH = 5. The isotherm study was done under the optimum conditions for each metal by applying the experimental results onto the well-known Freundlich and Langmuir models. The results show that the Langmuir is better in describing the isotherm adsorption of Pb(II) and Ni(II), while the Freundlich is a better fit in the case of Cu(II). Similarly, a kinetic study was performed by using the pseudo-first and second-order equations. Our results show that the pseudo-second-order is better in representing the kinetic adsorption of the three metal ions.

• Clean Technology
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• v.18 no.1
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• pp.76-82
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• 2012

The paper includes utlization of zeolite as potential adsorbent to remove a hazardous malachite green from waste water. The adsorption studies were carried out at 298, 308 and 318 K and effects of temperature, contact time, initial concentration on the adsorption were measured. On the basis of adsorption data Langmuir and Freundlich adsorption isotherm model were also confirmed. The equilibrium process was described well by Freundlich isotherm model, showing a selective adsorption by irregular energy of zeolite surface. From determined isotherm constants, zeolite could be employed as effective treatment for removal of malachite green. From kinetic experiments, the adsorption process followed the pseudo second order model, and the adsorption rate constant ($k_2$) decreased with increasing initial concentration of malachite green. Thermodynamic parameters like activation energy, change of free energy, enthalpy, and entropy were also calculated to predict the nature adsorption. The activation energy calculated from Arrhenius equation indicated that the adsorption of malachite green on the zeolite was physical process. The negative free energy change (${\Delta}G^{\circ}$ =-6.47~-9.07 kJ/mol) and the positive enthalpy change (${\Delta}H^{\circ}$ = +32.414 kJ/mol) indicated the spontaneous and endothermic nature of the adsorption in the temperature range 298~318 K.