• Environmental Engineering Research
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• v.16 no.2
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• pp.55-60
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• 2011

The removal of hexavalent chromium from aqueous solutions onto modified holly sawdust was studied at varying initial hexavalent chromium concentrations, adsorbent doses, pHs and contact times. The removal of hexavalent chromium from aqueous solutions increased with increasing adsorbent dosage and contact time. The percentage of hexavalent chromium removed from the aqueous solutions decreased with increasing hexavalent chromium concentration and pH of the solution. The kinetics of the adsorption of hexavalent chromium onto modified holly sawdust was analyzed using pseudo first-order and pseudo second-order models. The pseudo second-order model described the kinetics of adsorption of hexavalent chromium. The Langmuir and Freundlich isotherm models were used for modeling of the adsorption equilibrium data. The Langmuir isotherm model well described the equilibrium data for the removal of hexavalent chromium by modified holly sawdust. The obtained maximum adsorption capacity was 18.86 mg/g at pH 7. The results showed that modified holly sawdust can be used as a low cost adsorbent for the treatment of aqueous solutions containing chromium.

• Polymer(Korea)
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• v.38 no.5
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• pp.557-565
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• 2014

Sodium alginate and chitosan are added to a $CaCl_2$ solution to prepare calcium-alginate-chitosan and calciumalginate gels. After dehydration through stoving, two types of adsorbent particles are obtained. The adsorption process of the particles obtained for low concentrations of $Sr^{2+}$ satisfies a second-order kinetic equation and the Freundlich adsorption model. The thermodynamic behaviors of the particles indicate that adsorption occurs via a spontaneous physical process. XPS pattern analysis is used to demonstrate the adsorption of $Sr^{2+}$ by calcium alginate and chitosan. By building an interaction model of the molecules of chitosan and alginate with $Ca^{2+}$ and $Sr^{2+}$ to calculate energy parameters, Fukui index, Mulliken charge, and Mulliken population, adsorption of $Sr^{2+}$ on the molecular chains of chitosan as well as the boundary of calcium-alginate-chitosan is observed to show weak stability; by contrast, adsorption between molecular chains is high.

• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.224-229
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• 2011

Adsorption characteristics of erythrosine dye onto the activated carbon has been investigated in a batch system with respect to initial concentration, contact time and temperature. Kinetic studies of the adsorption of erythrosine were carried out at 298 K, using aqueous solutions with 100, 250 and 500 mg/L concentration of erythrosine. The adsorption process followed a pseuo second order model, and the adsorption rate constant (k2) decreased with increasing the initial concentration of erythrosine. The equilibrium process can be well discribed by Freundlich isotherm in the temperature range from 298 to 318 K. Free energy of adsorption (${\Delta}G^o$), enthalpy (${\Delta}H^o$), and entropy (${\Delta}S^o$) change were calculated to predict the nature the adsorption. The estimated values for ${\Delta}G^o$ were -3.72~-9.62 kJ/mol over the activated carbon at 250 mg/L, indicated toward a spontaneous process. The positve value for ${\Delta}H^o$ indicates that the adsorption of erythrosine dye on activated carbon is an endothermic process.

• Environmental Engineering Research
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• v.20 no.1
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• pp.73-78
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• 2015

The aim of this study was to examine the phosphate (P) removal by quintinite from aqueous solutions. Batch experiments were performed to examine the effects of reaction time, temperature, initial phosphate concentration, initial solution pH and stream water on the phosphate adsorption to quintinite. Kinetic, thermodynamic and equilibrium isotherm models were used to analyze the experimental data. Results showed that the maximum P adsorption capacity was 4.77 mgP/g under given conditions (initial P concentration = 2-20 mgP/L; adsorbent dose = 1.2 g/L; reaction time = 4 hr). Kinetic model analysis showed that the pseudo second-order model was the most suitable for describing the kinetic data. Thermodynamic analysis indicated that phosphate sorption to quintinite increased with increasing temperature from 15 to $45^{\circ}C$, indicating the spontaneous and endothermic nature of sorption process (${\Delta}H^0=487.08\;kJ/mol$; ${\Delta}S^0=1,696.12\;J/(K{\cdot}mol)$; ${\Delta}G^0=-1.67$ to -52.56 kJ/mol). Equilibrium isotherm analysis demonstrated that both Freundlich and Redlich-Peterson models were suitable for describing the equilibrium data. In the pH experiments, the phosphate adsorption to quintinite was not varied at pH 3.0-7.1 (1.50-1.55 mgP/g) but decreased considerably at a highly alkaline solution (0.70 mgP/g at pH 11.0). Results also indicated that under given conditions (initial P concentration=2 mgP/L; adsorbent dose=0.8 g/L; reaction time=4 hr), phosphate removal in the stream water (1.88 mgP/g) was lower than that in the synthetic solution (2.07 mgP/g), possibly due to the presence of anions such as (bi)carbonate and sulfate in the stream water.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.477-482
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• 2015

This study examined the adsorption characteristics of heavy metal ions ($Cr^{6+}$, $As^{3+}$) in an aqueous solution using recycled aggregate (RA) and recycled aggregate (RA)/steel slag (SS) composites. The RA and SS are favorable for the absorbent because it contains about 91% and 86.9%, respectively, which are some of the major adsorbent ingredients (CaO, $SiO_2$, $Al_2O_3$ and $Fe_2O_3$) for heavy metal. Kinetic equilibrium of $Cr^{6+}$ and $As^{3+}$ in RA and RA/SS composites reached within 180 min and 360 min, respectively. The kinetic data presented that the slow course of adsorption follows the Pseudo first and second order models. The equilibrium data were well fitted by the Freundlich model and showed the affinity order of $As^{3+}$ > $Cr^{6+}$. The results of $As^{3+}$ also showed that the adsorption capacity slightly increased with increasing pH from 6 to 10. Meanwhile, the adsorption capacity of $Cr^{6+}$ was slightly decreased. From these results, it was concluded that the RA and RA/SS composites can be successfully used for removing the heavy metals ($Cr^{6+}$ and $As^{3+}$) from aqueous solutions.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.61-68
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• 2009

The main objective of this study was to examine the removal of heavy metals from water by inflated vermiculites. The component of vermiculites was analyzed by XRF, and the concentration of metal ion was measured by ICP-AES. Serial batch kinetic tests and batch sorption tests were conducted to determine the removal characteristics for heavy metals in aqueous solutions. As a result, solution pH values of tests with the inflated vermiculites generally increased and then stabilized. Equilibrium pHs were generally established within 5 hrs. In addition, removal rates of inflated vermiculites were tested at the initial concentration of 3 mg/L. As a result, at equilibrium concentration, except for chromium (36.23%), Most of the heavy metals were effectively removed (96.08~98.54%). Finally, sorption data were correlated with both Langmuir and Freundlich isotherms. The Qmax obtained from Langmuir isotherm were determined to Pb $725.4mg\;kg^{-1}$, Cd $568.8mg\;kg^{-1}$, Zn $540.2mg\;kg^{-1}$, Cu $457.2mg\;kg^{-1}$ Cr $0.9mg\;kg^{-1}$ respectively. The results of the study indicate that inflated vermiculites can be properly used as an adsorbent for various heavy metals because of its outstanding removal rate.

• 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).

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.283-289
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• 2021

Adsorption characteristics of carbol fuchsin (CF) dye by coal-based activated carbon (CAC) were investigated using pH, initial concentration, temperature and contact time as adsorption variables. CF dissociates in water to have a cation, NH₂⁺, which is bonded to the negatively charged surface of the activated carbon in the basic region by electrostatic attraction. Under the optimum condition of pH 11, 96.6% of the initial concentration was adsorbed. Isothermal adsorption behavior was analyzed using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. Langmuir's equation was the best fit for the experimental results. Therefore, the adsorption mechanism was expected to be adsorbed as a monolayer on the surface of activated carbon with a uniform energy distribution. From the evaluated Langmuir's dimensionless separation coefficients (R_L = 0.503~0.672), it was found that CF can be effectively treated by activated carbon. The adsorption energies determined by Temkin and Dubinin-Radushkevich models were E = 15.31~7.12 J/mol and B = 0.223~0.365 kJ/mol, respectively. Therefore, the adsorption process was physical (E < 20 J/mol, B < 8 kJ/mol). The experimental result of adsorption kinetics fit better the pseudo second order model. In the adsorption reaction of CF dye to CAC, the negative free energy change increased as the temperature increased. It was found that the spontaneity also increased with increasing temperature. The positive enthalpy change (40.09 kJ/mol) indicated an endothermic reaction.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.636-645
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• 2022

In this study, we investigated the adsorption characteristics of methyl orange (MO), an anionic dye, on ginkgo shell-based activated carbon (AC). For this purpose, ACs (GS-1, GS-2, and GS-4) with different textural properties were prepared using ginkgo shells and potassium hydroxide (KOH), a representative chemical activating agent. The correlation between the textural characteristics of AC prepared and the mixing ratio of KOH was investigated using nitrogen adsorption/desorption isotherms. The MO adsorption equilibrium experiment on the prepared ACs was conducted under different pH (pH 3~11) and temperature (298~318 K) conditions, and the results were investigated by Langmuir, Freundlich, Sips and temperature-dependent Sips equations. The feasibility of the MO adsorption treatment process of the prepared AC was also investigated using the dimensionless Langmuir separation factor. The heterogeneous adsorption properties of MO for the prepared AC examined using the adsorption energy distribution function (AED) were closely related to the system temperature and textural characteristics of AC. The kinetic results of the batch adsorption performed at different temperatures can be satisfactorily explained by the homogeneous surface diffusion model (HSDM), which takes into account the external mass transfer, intraparticle diffusion, and active site adsorption. The relationship between the activation energy value obtained by the Arrhenius plot and the adsorption energy distribution function value was also investigated. In addition, the adsorption process mechanism of MO on the prepared AC was evaluated using Biot number.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.8
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• pp.606-616
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• 2011

The objectives of this study were to evaluate the applicability of adsorption models for adsorption properties of adsorbents. For this study, adsorption experiment of $NO_3^-$ ion using anion exchange resin has been investigated under adsorption equilibrium and kinetic in bach process. Adsorption equilibrium experiment were carried out that two conditions is change of adsorbate concentration and change of adsorbent weight. Experiment results have been analyzed by adsorption isotherm models, energy models and kinetic models. Under the condition of change of adsorbate concentration was best described by Sips and Redlich-Perterson isotherm models. However case of change of adsorbent weight was described by Langmuir isotherm models. It seems reasonable to assume that isotherm model was dominated by multiple mechanism according to experiment condition.