• Applied Chemistry for Engineering
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• v.26 no.5
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• pp.581-586
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• 2015

Adsorption of Safranin using granular activated carbon from aqueous solution was investigated. Batch experiments were carried out as a function of adsorbent dose, initial concentration, contact time and temperature. The equilibrium adsorption data were fitted to Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. Based on an estimated Langmuir separation factor, $R_L=0.183{\sim}0.254$ and a Freundlich separation factor, 1/n = 0.518~0.547, this process could be employed as an effective treatment method. Adsorption data were also modeled using the pseudo-first and second-order kinetic equations. It was shown that the pseudo-second-order kinetic equation could best describe the adsorption kinetics. The negative Gibbs free energy (${\Delta}G=-3.688{\sim}-7.220kJ/mol$) and positive enthalpy (${\Delta}H=33.126kJ/mol$) indicated that the adsorption process was spontaneous and endothermic.

• Korean Journal of Food Science and Technology
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• v.31 no.1
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• pp.164-170
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• 1999

Cracking of rice caused by moisture migration during storage under different relative humidity conditions was investigated for the establishment of safe storage condition of rice. Rice was cracked when a large difference in equilibrium relative humidity $({\Delta}ERH)$ between the rice and the environment was present. External and internal cracks were generated as the results of moisture desorption and adsorption, respectively. The external cracks by moisture desorption generated in all directions and shaped irregularly, while the internal cracks by moisture adsorption did in radial direction and showed a typical shape. The cracking trend could be analyzed by the Weibull function, and the cracking constant increased with ${\Delta}ERH$. The frequency of cracked rice increased linearly with In $({\Delta}ERH)$. The critical crack-inducing ${\Delta}ERH$ was $11.3{\sim}16.4%$ during desorption and $10.8{\sim}17.1%$ during adsorption. A diagram for the safe storage of rice was developed with respect to the initial moisture content and the water activity of rice.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.8
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• pp.450-457
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• 2015

In this research a adsorbent, PVA-Zeolite bead, was prepared by immobilizing zeolite with PVA. The results of XRD and SEM analysis showed that the prepared PVA-Zeolite beads had porous structure and the zeolite particles were in mobilized within the internal matrix of the beads. The adsorption properties of Sr ion and Cs ion with the adsorbent were studied by different parameters such as effect of pH, adsorption rate, and adsorption isotherm. The adsorption of Sr ion and Cs ion reached equilibrium after 540 minutes. The adsorption kinetics of both ions by the PVA-Zeolite beads were fitted well by the pseudo-second-order model more than pseudo-first-order model. The equilibrium data fitted well with Langmuir isotherm model. The maximum adsorption capacities of Sr ion and Cs ion calculated from Langmuir isotherm model were 52.08 mg/g and 58.14 mg/g, respectively. The external mass transfer step was very fast compared to the intra-particle diffusion step in the adsorption process of Cs ion and Sr ion by the PVA-Zeolite beads. This result implied that the rate controlling step was the intra-particle diffusion step.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.21-27
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• 2018

FRN (Full range Naphtha) is distilled from crude oil in a Naphtha Splitter Unit and is separated into the Light Straight Naphtha, Heavy Naphtha, and kerosene according to the boiling point in sequence. This separation is conducted using a series of binary-like columns. In this separation method, the energy consumed in the reboiler is used to separate the heaviest components and most of this energy is discarded as vapor condensation in the overhead cooler. In this study, the first two columns of the separation process are replaced with the Petlyuk column. A structural design was exercised by a stage to stage computation with an ideal tray efficiency in the equilibrium condition. Compared to the performance of a conventional system of 3-column model, the design outcome indicates that the procedure is simple and efficient because the composition of the liquid component in the column tray was designed to be similar to the equilibrium distillation curve. An analysis of the performance of the new process indicated an energy saving of 12.3% under same total number of trays and with a saving of the initial investment cost.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.9_10
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• pp.417-420
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• 2008

We consider the problem of optimizing the performance of a system shared by selfish non-cooperative users. In this problem, small jobs which the users request should be scheduled on a set of shared machines with their speed functions, each of which dependson the amount of jobs allocated on a machine. The performance of the system is measured by the maximum of the completion times when the machines complete the jobs allocated on them. The selfish users can choose a machine on which their jobs are executed, and they choose the fastest machine. But it typically results in suboptimal system performance. The Price of Anarchy(PoA) was introduced as a measure of the performance degradation due to the user's selfish behavior. The PoA is the worst-case ratio of the cost of a Nash equilibrium to the optimal cost. In this paper, we estimate the PoA for the above scheduling problem.

• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.248-253
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• 2006

In order to develope an efficient drug delivery system, experimental researches on the supercritical impregnation of ibuprofen onto mesoporous silica, MCM-41,and its drug release characteristics were performed. Supercritical carbon dioxide was adapted as an alternative solvent as it is harmless and able to avoid defects of organic solvents in drug manufacturing processes. The procedure was composed of three steps, that is, as hydrothermal synthesis of MCM-41, supercritical impregnation of ibuprofen onto MCM-41 and release of impregnated ibuprofen. Supercritical impregnation reached equilibrium within 2 h for all cases of this research and the amount of equilibrium impregnation increased with solubility of ibuprofen in supercritical carbon dioxide. Release profiles of impregnated ibuprofen showed a similar behavior for all MCM-41 with different impregnated ibuprofen.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.300-309
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• 2010

The ability of sodium-exchanged clay particles as an adsorbent for the removal of commercial dyes, Methylene blue (MB) and Malachite green oxalate (MG) from aqueous solutions has been investigated under various experimental conditions. The effect of the experimental parameters, such as pH solution, agitation time, adsorbate concentration and adsorbent dose were examined. Maximum adsorption of dyes, i.e. >90% has been achieved in aqueous solutions using 0.03 g of clay at a pH of 7 and 298 K for both dyes. The adsorption process was a fast and the equilibrium was obtained within the first 5 min. For the adsorption of both MB and MG dyes, the pseudo-second-order reaction kinetics provides the best correlation of the experimental data. The adsorption equilibrium results follow Langmuir and Dubini-Radushkevich (D-R) isotherms with high regression coefficients $R^2$ > 0.98. The mean free energies $E_a$ of adsorption from D-R model were 3.779 and 2.564 kj/mol for MB and MG respectively, which corresponds to a physisorption process.

• Journal of the Korea Computer Graphics Society
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• v.7 no.4
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• pp.9-18
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• 2001

There was much previous work to represent effects which are used in the real world paintings. In case of Western paintings like as watercolor or oil painting, largely conversion techniques from photo images were researched. However, in case of Oriental paintings, the development of a conversion technique is not easy because a few strokes are used to represent objects. Then, model-based approach was studied to draw Oriental paintings. In this paper, a model-based approach for Oriental paintings is described. In our model, to represent the diffusion effects, LEM(Local Equilibrium Model) is proposed. LEM is a method to calculate the movement of water and ink effectively. Also, a layer model for paper is proposed to discriminate wet or dry state. And a brush model to draw strokes is described.

• Clean Technology
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• v.7 no.2
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• pp.141-149
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• 2001

The effects of various factors such as adsorption temperature, interstitial velocity, species and concentration of adsorbates(benzene and toluene) and aspect ratio(L/D) on adsorption characteristics were investigated in a fixed bed with activated carbon. The breakthrough time in a fixed bed was decreased with the increasing of adsorption temperature, interstitial velocity and concentration of adsorbates. The interstitial velocity, concentration of adsorbates and adsorption temperature had influenced considerably upon the MTZ(mass transfer zone) and LUB(length of unused bed) obtained through the breakthrough curves, while aspect ratio(L/D) had smaller effect than former factors. Especially, the concentration of adsorbates among factors have the largest effect on MTZ and LUB. From comparison with the model isotherms, such as the Langmuir, Freundlich and Langmuir-Freundlich, the experimental isotherm data of benzene and toluene agreed farily well to three adsorption isotherm models.

• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.514-519
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• 2017

Adsorption characteristics of acid green 27 dye using activated carbon were investigated as function of adsorbent dose, pH, initial concentration, contact time and temperature. Freundlich isotherm explained adsorption of acid green 27 dye very well and Freundlich separation factors (1/n=0.293~0.387) were found that this process could be employed as effective treatment method. Kinetic studies showed that the kinetic data were well described by the pseudo second-order kinetic model. Pseudo second rate constant ($k_2$) decreased with the increase in initial acid green 27 concentration. Activation energy (10.457 kJ/mol) and enthalpy (79.946 kJ/mol) indicated that adsorption process was physisorption and endothermic. Since Gibbs free energy decreased with increasing temperature, spontaneity of adsorption reaction increased with increasing temperature in the temperature range of 298 K~318 K.