• Carbon letters
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• v.14 no.4
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• pp.234-242
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• 2013

Potassium hydroxide-activated carbons (CK21, CK11, and CK12) were prepared from pistachio nutshells. Physicochemical properties of activated carbons were characterized by TGA, $pH_{pzc}$, Fourier transform infrared spectroscopy, scanning electron microscopy, and $N_2$-adsorption at $-196^{\circ}C$. The examinations showed that activated carbons have high surface area ranging between 695-1218 $m^2/g$, total pore volume ranging between 0.527-0.772 mL/g, and a pore radius around 1.4 nm. The presence of acidic and basic surface C-O groups was confirmed. Batch adsorption experiments were carried out to study the effects of adsorbent dosage, temperature, initial concentration of adsorbate, and contact time on deltamethrin adsorption by activated carbons. The kinetic studies showed that the adsorption data followed a pseudo-second order kinetic model. The Langmuir model showed a maximum adsorption capacity of 162.6 mg/g at $35^{\circ}C$ on CK12. Thermodynamic studies indicated that adsorption was spontaneous and increased with temperature, suggesting an endothermic process.

• Journal of Environmental Science International
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• v.23 no.7
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• pp.1289-1297
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• 2014

In this study, PVC-LMO beads were prepared by immobilizing lithium manganese oxide (LMO) with poly vinyl chloride (PVC) diluted in dioxane solvent. XRD and SEM analysis confirmed that LMO was immobilized well in PVC-LMO beads. The diameter of PVC-LMO beads prepared by dioxane solvent was about 2 mm. The adsorption experiments of lithium ions by PVC-LMO beads were conducted batchwise. The optimum pH was pH 10. The adsorption characteristics of lithium ions by PVC-LMO beads was well described by the pseudo-second-order kinetic model. The maximum adsorption capacity obtained from Langmuir model was 24.25 mg/g. The thermodynamic parameters such as ${\Delta}H^{\circ}$, ${\Delta}S^{\circ}$ and ${\Delta}G^{\circ}$ were evaluated. The calculated ${\Delta}G^{\circ}$ was between -6.16 and -4.14 kJ/mol (below zero), indicating the spontaneous nature of $Li^+$ adsorption on PVC-LMO beads. Also, the results showed that PVC-LMO beads prepared in this study could be used for the removal of lithium ions from seawater containing coexisting ions such as $Na^+$, $K^+$, $Mg^{2+}$ and $Ca^{2+}$.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.795-805
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• 2016

Nonlinear normal modes(NNMs) is a branch of periodic solution of nonlinear dynamic systems. Determination of stable periodic solution is very important in many engineering applications since the stable periodic solution can be an attractor of such nonlinear systems. Periodic solutions of nonlinear system are usually calculated by perturbation methods and numerical methods. In this study, numerical method is used in order to calculate the NNMs. Iteration of the solution is presented by multiple shooting method and continuation of solution is presented by pseudo-arclength continuation method. The stability of the NNMs is analyzed using Floquet multipliers, and bifurcation points are calculated using indirect method. Proposed analyses are applied to two nonlinear numerical models. In the first numerical model nonlinear spring-mass system is analyzed. In the second numerical model Jeffcott rotor system which has unstable equilibria is analyzed. Numerical simulation results show that the multiple shooting method can be applied to self excited system as well as the typical nonlinear system with stable equilibria.

• Journal of Korean Society on Water Environment
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• v.25 no.3
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• pp.459-463
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• 2009

The adsorption features of malachite green onto activated carbon have been investigated for its treatment from aqueous solution. The influential factors were examined the initial concentration of malachite green, reaction temperature, and pH. Under experimental conditions, adsorption equilibrium of malachite green was attained within 2 hr after the adsorption started. The adsorption reaction of malachite green followed the pseudo-second order rate model, and the adsorption rate constants(k2) decreased with increasing initial concentrations of malachite green. Adsorption behavior of malachite green on activated carbon was found to follow the Freundlich model well in the initial adsorbate concentration range. With increase in temperature, the adsorbed amount of malachite green at equilibrium increased, which indicate that the adsorption reaction was endothermic reaction. Thermodynamic parameters for malachite green adsorption reaction were estimated at varying temperatures, and in the pH range of 2-10, adsorption of malachite green increased.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.211-215
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• 2018

Chitosan was modified by gamma radiation-induced grafting with maleic acid and then used for the removal of cobalt ions from aqueous solutions. Chitosan-g-maleic acid was characterized by Fourier Transform infrared spectroscopy (FT-IR). The effect of the dose (1-5 kGy) and monomer concentration (0.3-1.3%, m/v) on the grafting ratio was examined. The adsorption kinetics and isotherms were also investigated. The results showed that the optimal dose for grafting was 2 kGy. When monomer concentration was within the range of 0.3-1.3% (m/v), the grafting ratio increased almost linearly. For the adsorption of cobalt ions by chitosan-g-maleic acid beads, the pseudo second-order kinetic model ($R^2=0.99$) and Temkin isotherm model ($R^2=0.96$) were able to fit the experimental data reasonably well. The equilibrium adsorption capacity of cobalt ions increased from 2.00 mg/g to 2.78 mg/g after chitosan modification.

• Environmental Engineering Research
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• v.25 no.3
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• pp.426-438
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• 2020

In this study, cherry kernel shell pyrolytic charcoal was synthesized (CKSC) and composite beads were obtained by blending this pyrolytic charcoal with chitosan and Fe₂O₃ nanoparticles (Fe-C-CKSC). Cr(VI) adsorption from aqueous solutions by Fe-C-CKSC composite beads and CKSC adsorbents was studied comparatively. The effects of Cr(VI) initial concentration, adsorbent dosage, contact time, pH and temperature parameters on Cr(VI) adsorption were investigated. Adsorption reached an equilibrium point within 120 min for CKSC and Fe-C-CKSC adsorbents. The maximum Cr(VI) removal was obtained at the initial pH value of 1.56 for CKSC and 2.00 for Fe-C-CKSC. The optimum adsorbent dosage was found to be 5 g/L for CKSC and 3 g/L for Fe-C-CKSC. Based on the Langmuir model, the maximum adsorption capacities were calculated as 14.455 mg/g and 47.576 mg/g for CKSC and Fe-C-CKSC, respectively. Thermodynamic and kinetic studies were performed. As a result of adsorption kinetics calculations, adsorption was found to be consistent with the pseudo second order kinetic model. Characterization of the synthesized adsorbents was performed by SEM, BET, FTIR and elemental analysis. This study has shown that low cost adsorbents CKSC and Fe-C-CKSC can be used in Cr(VI) removal from aqueous solutions.

• Membrane and Water Treatment
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• v.6 no.6
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• pp.439-449
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• 2015

Carbolic Acid which is called phenol is one of the important starting and/or intermediate materials in various industrial processes. However, its excessive release into environment poses a threat to living organisms, as it is a highly carcinogens and hazardous pollutant even at the very low concentration. Thus removal of phenol from polluted environments is very crucial for sustainable remediation process. We developed a low cost adsorption method for separating phenol from a model aqueous solution. The phenol adsorption was studied using two adsorbents i.e., Amber lite XAD-16 and Amber lite XAD-7 HP with a constant amount of resin 0.1 g at varying aqueous phenol concentrations ($50-200mgL^{-1}$) at room temperature. We compared the efficacy of two phenol adsorbents for removing higher phenol concentrations from the media. We investigated equilibrium and kinetics studies of phenol adsorption employing Freundlich, Temkin and Langmuir isotherms. Amberlite XAD-16 performed better than Amberlite XAD-7 HP in terms of phenol removal efficiency that amounted to 95.52%. Pseudo second order model was highly fitted for both of the adsorption systems. The coefficient of determination ($R^2$) with Langmuir isotherm was found to be 0.98 for Amberlite XAD-7 HP. However, Freundlich isotherm showed $R^2$ value of 0.95 for Amberlite XAD-16, indicating that both isotherms could be described for the isotherms on XAD-7 HP and Amberlite XAD-16, respectively.

• Carbon letters
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• v.9 no.1
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• pp.8-16
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• 2008

Oxidized activated carbons were prepared by reacting steam-activated carbon developed from pecan shells with nitric acid of varying strength (15, 30, 45 and 60%). The textural properties and the chemistry of the surface of the non-oxidized and of the oxidized carbons were determined from nitrogen adsorption and base neutralization capacities. The uptake of Pb(II) and Cd(II) from aqueous solution by these carbons was determined by kinetic and equilibrium experiments as well as by the column method. Treatment with nitric acid brought about drastic decrease in surface area and remarkable increase in the pore size of the carbon with these changes depending on the strength of nitric acid. Nitric acid increased the surface acidity by developing new surface oxygen functional groups of acidic nature. $HNO_3$-oxidized carbons exhibited high adsorption capacities for Pb(II) and Cd(II). The adsorption of these ions increased with the decrease of the surface pH of the carbon and with the increase of the solution pH from 2.5 to 6 and 7. The amount adsorbed from lead and cadmium was also related to the amount of surface acidity, the pH of the point of zero charge and on some metal ion parameters. Cadmium and lead uptake by the investigated carbons followed pseudo-second order model and the equilibrium sorption data fitted Langmuir adsorption model.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.562-568
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• 2019

Cylindrical shape extrudates of calcium silicate hydrate (CSH) were prepared using different percentages of polyvinyl alcohol (PVA) / sodium alginate (SA) mixtures as binders and an aqueous solution containing 6% $H_3BO_3$ and 3% $CaCl_2$ was used as a cross linking agent. As the quantity of alginate increases, the phosphate removal efficiency and capacity were decreased. Among four different extrudate samples, the sample prepared by 8% PVA + 2% SA showed the highest phosphate removal efficiency (59.59%) and capacity (29.97 mg/g) at an initial phosphate concentration of 100 ppm and 2.0 g/L adsorbent dosage. Effects of the adsorbent dosage, contact time and initial phosphate concentration on the sample were further studied. The removal efficiency and capacity obtained by a 4.0 g/L adsorbent dose at an initial phosphate concentration of 100 ppm in 3 h were 79.38% and 19.96 mg/g, respectively. The experimental data of kinetic and isotherm measurements followed the pseudo-second-order kinetic equation and Langmuir isotherm model, respectively. These results suggested that the phosphate removal was processed via a chemisorption and a monolayer coverage of phosphate anions was on the CSH surface. The maximum adsorption capacity ($q_{max}$) was calculated as 23.87 mg/g from Langmuir isotherm model.

• Journal of Environmental Science International
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• v.27 no.12
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• pp.1215-1226
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• 2018

In this study, PAN-SZ (polyacrylonitrile scoria zeolite) beads were prepared by immobilizing Na-A zeolite (SZ-A) synthesized from Jeju volcanic rocks (scoria) on the polymer PAN. FT-IR and TGA analysis results confirmed that the SZ-A was immobilized in the PAN-SZ beads. SEM images showed that the PAN-SZ beads are a spherical shape with 2 mm diameter and exhibit a porous inner structure inside the bead. The most suitable mixing ratio of PAN to SZ-A as the adsorbent for removing Sr ions was PAN/SZ-A = 0.2 g/0.3 g. The adsorption kinetic data for Cu and Sr ions were fitted well with the pseudo-second-order model. The Cu and Sr ion uptakes followed a Langmuir isotherm model and the maximum adsorption capacities at $20^{\circ}C$ were 84.03 mg/g and 75.19 mg/g, respectively. The amount of Sr ion adsorbed by SZ-A on the PAN-SZ beads was about 160 mg/g, which was similar to that adsorbed by SZ-A powder. Thus, the PAN-SZ beads prepared in this study are considered to be effective adsorbents for removing metal ions in aqueous solutions.