• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.33-38
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• 2005

The distribution of vanadium and iron ionic species in the presence of picolinate ligand has been simulated at various conditions with different pH values and compositions in the decontamination waste solution. In spite of variations of metal concentration in the decontamination solution, the shape of distribution diagrams were not changed greatly at both high (the molar ratio of picolinate to vanadium is 6) and low (the molar ratio is 3) LOMI decontamination conditions. However, in the solution of low-picolinate condition the shape of the distribution diagram of iron(II)-picolinate complexes was changed significantly. This phenomenon is attributed to the shortage of relative amount of picolinate ligand to iron existed in the solution, and originated from the difference in stability constants for complexes formed between vanadium(III) and iron(II) species with picolinate ligand. The distribution diagrams obtained in this study can be applied very usefully to the prediction or understanding the reaction phenomena occurred at various conditions in the course of the LOMI waste treatments such as an ion exchange operation.

• Korean Chemical Engineering Research
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• v.56 no.5
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• pp.679-686
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• 2018

Reverse osmosis (RO) concentration of sodium chloride, sodium acetate, and sodium citrate solutions has been performed by polyamide RO membrane. Concentration polarization phenomena was also studied by changing pressure, solute kinds, and initial solution concentration. Pressure effect on permeation flux was that the increase of flux was accompanied by the increase of pressure. Flux increase was observed by the decrease of initial solution concentration. Surface concentration on the RO membrane increases and so flux declines due to the concentration polarization. In the later phase of concentration, concentration polarization effect was decreased by the back diffusion of solute from the polariztion layer. In case of sodium citrate, its large ion size and charge density resulted in the discrepancy between theory and experimental data of concentration polarization. It may be due to electric repulsion on the membrane surface.

• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.226-233
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• 2007

In this study, the effects of additives such as ionic surfactant and cosurfactant were studied on the solubilization of sulfur compounds contained in the crude oil by Tergitol series nonionic surfactants. It was found that the addition of an ionic surfactant such as sodium oleate, potassium oleate, CTAB and DTAB did not enhance solubilization capacity of Tergitol series nonionic surfactant. On the other hand, the addition of a long-chain alcohol as a cosurfactant increased the solubilization of sulfur compounds in the crude oil. The effect of alcohol was found to become reduced with an increase in the amount of crude oil used mainly due to partitioning phenomena of an nonionic surfactant. The enhancement of solubilizing capacity of Tergitol series nonionic surfactant with addition of a cosurfactant was associated with a decrease in interfacial tension between crude oil and surfactant solution. The pH of Tergitol nonionic surfactant solution did not affect the solubilization of sulfur compounds. Finally, it was found that the growth of sulfur reducing microoganisms was not greatly affected by both addition of nonionic surfactant and cosurfactant.

• Korean Journal of Materials Research
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• v.12 no.7
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• pp.528-532
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• 2002

Anodic $TiO_2$film on Ti substrate was fabricated at 180V in sulfuric acid solutions containing phosphoric acid and hydrogen peroxide. Effects of the anodizing conditions on the morphology of the oxide layers, and chemical states of the component elements of the layers were studied primarily using SEM, XRD, AFM, and XPS. The pores in the oxide layer was not uniform in size, shape, and growth direction particularly near the interface between the substrate and the oxide layer, compared with those of the surface layer. The formation of irregular type of pores seemed to be attributed to spark discharge phenomena which heavily occurred during increasing the anodic voltage. The pore diameter and the cell size increased, and the number of cells per unit area decreased with the increasing time. From the XPS results, it was shown that component elements of the electrolytes, P and S, existed in the chemical states of $PO_4^{-3}$ , $P_2$$O_{5}$, $SO_4^{-2}$ , $SO_3^{-2}$ , P, S, etc., which were penetrated from the electrolytes into the oxide layer during anodization.

• Fire Science and Engineering
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• v.31 no.4
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• pp.35-42
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• 2017

Large Eddy Simulation (LES) was peformed for the backdraft occurred in a compartment filled with high-temperature methane fuel using the Fire Dynamics Simulator (FDS) of version 6. The prediction performance of FDS, adopted the Eddy Dissipation Concept (EDC) combustion model with five different chemical reaction mechanisms, was evaluated. The temporal distributions of temperature, fuel mass fraction, velocity and pressure were discussed with numerical results and the pressure variation in time was compared with that of previous experiment. The FDS adopted the EDC model showed the possibility of LES for the backdraft phenomena. However, the prediction performance of the LES with EDC model strongly depended on the chemical reaction mechanism considered. It is necessary that the suitability of the chemical reaction mechanism should be validated in advance for LES with the FDS v6 to be applied to the simulation of backdraft.

• Journal of the Korean Chemical Society
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• v.28 no.1
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• pp.62-69
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• 1984

The reaction of toluene with ethanol was studied over various cation-exchanged pentasil zeolite catalysts. The toluene disproportionation reaction to produce xylenes increased with increasing reaction temperature and the activity of alkylation of toluene with ethanol showed maximum at around $400^{\circ}C$. Only Cs-ZSM-5 catalyst showed pronounced p-ethyltoluene selectivity increasing to 96% with increasing degree of Cs-exchange. The sorption rate of m-xylene was lower for Cs-exchanged ZSM-5 than H-ZSM-5 catalyst. These phenomena were interpreted in terms of shape selectivity arising from the partial blocking of channel intersections by large cesium ions.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.65-70
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• 2002

We have evaluated the specific hydroxyl group-solvent and carbonyl group-solvent interactions by using an Alltima C18 stationary phase and by measuring the retention data of carefully selected solutes in 60/40, 70/30, and 80/20(v/v%) acetonitrile/water eluents at 25, 30, 35, 40, 45, and 50 oC. The selected solutes are phenol, acetophenone, alkylbenznes(benzene to hexylbenznene), 4 positional isomers of phenylbutanol, 5-phenyl-1-pentanol, 3 positional isomers of alkylarylketone derived from butylbenzene, and 1-phenyl-2-hexanone. The magnitudes of hydroxyl group-acetonitrile/water specific interaction enthalpies are larger than those of carbonyl group-acetonitrile/water specific interaction enthalpies in general while the magnitudes of carbonyl group-methanol/water specific interaction enthalpies are larger than those of hydroxyl group-methanol/water specific interactions. We observed clear discrepancies in functional group-solvent specific interaction among positional isomers. The variation trends of solute transfer enthalpies and entropies with mobile phase composition in the acetonitrile/water system are much different from those in the methanol/water system. The well-known pocket formation of acetonitrile in aqueous acetonitrile mixtures has proven to be useful to explain such phenomena.

• Journal of the Korean Chemical Society
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• v.42 no.3
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• pp.292-296
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• 1998

The elution behavior of copper(Ⅱ) and iron(Ⅱ) ions by phenol sulfonic acid(PSA) as an eluent on chelating resin, Amberlite IRC-718 have been investigated. When copper(Ⅱ) and iron(Ⅱ) solutions were adsorbed on the resin and eluted with various concentration of PSA, two peaks of each ion were appeared in the elution curve. These two peak areas were changed according to the PSA concentration. Using these phenomena, the stability constants of complex formation between the two ions and PSA were calculated. The values are 7.0 for copper(II) and $4.5{\times}10^4$ for iron(II), respectively.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1679-1684
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• 2011

Interfacial reactions kinetics often differ from kinetics of bulk reactions. Here, we describe how the density change of an immobilized reactant influences the kinetics of interfacial reactions. Self-assembled monolayers (SAMs) of alkanethiolates on gold were used as a model interface and the Diels-Alder reaction between immobilized quinones and soluble cyclopentadiene was used as a model reaction. The kinetic behavior was studied using varying concentrations of quinones. An unusual threshold density of quinones (${\Gamma}_c$ = 5.2-7.2%), at which the pseudo-first order rate constant started to vary as the reaction progressed, was observed. This unexpected kinetic behavior was attributed to the phase-separation phenomena of multi-component SAMs. Additional experiments using more phase-separated two-component SAMs supported this explanation by revealing a significant decrease in ${\Gamma}_c$ values. When the background hydroxyl group was replaced with carboxylic or phosphoric acid groups, ${\Gamma}_c$ was observed at below 1%. Also, more phase-separated thermodynamically controlled SAMs produced a lower critical density (3% < ${\Gamma}_c$ < 4.9%) than that of the less phaseseparated kinetically controlled SAMs (6.5% < ${\Gamma}_c$ < 8.9%).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.6
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• pp.225-231
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• 2008

For an aspect ratio (transport length-to-width) of 5, Pr=1.13, Le=1.91, Pe=4.3, Cv=1.01, $P_B=20\;Torr$, the effects of addition of inert gas Ne on thermally buoyancy-driven convection ($Gr=2.44{\times}10^3$) are numerically investigated for further understanding and insight into essence of transport phenomena in two dimensional horizontal enclosures. For $10K{\leq}{\Delta}T{\leq}50\;K$, the crystal growth rate increases from 10 K up to 20 K, and then is slowly decreased until ${\Delat}T=50\;K$, which is likely to be due to the effects of thermo-physical properties stronger than the temperature gradient corresponding to driving force for thermal convection. The dimensional maximum velocity gratitude reflecting the intensity of thermal convection is directly and linearly proportional to the temperature difference between the source and crystal regions. The rate is first order-exponentially decreased for $2{\leq}Ar{\leq}5$. This is related to the finding that the effects of side walls tend to stabilize convection in the growth reactor. In addition, the rate is first order exponentially decayed for $10{\leq}P_B{\leq}200\;Torr$.