• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.565-573
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• 2021

Isotherms, kinetics and thermodynamic properties for adsorption of Brilliant Green(BG), Quinoline Yellow(QY) dyes by activated carbon were carried out using variables such as dose of adsorbent, pH, initial concentration, contact time, temperature and competitive. BG showed the highest adsorption rate of 92.4% at pH 11, and QY was adsorbed at 90.9% at pH 3. BG was in good agreement with the Freundlich isothermal model, and QY was well matched with Langmuir model. The separation coefficients of isotherm model indicated that these dyes could be effectively treated by activated carbon. Estimated adsorption energy by Temkin isotherm model indicated that the adsorption of BG and QY by activated carbon is a physical adsorption. The kinetic experimental results showed that the pseudo second order model had a better fit than the pseudo first order model with a smaller in the equilibrium adsorption amount. It was confirmed that surface diffusion was a rate controlling step by the intraparticle diffusion model. The activation energy and enthalpy change of the adsorption process indicated that the adsorption process was a relatively easy endothermic reaction. The entropy change indicated that the disorder of the adsorption system increased as the adsorption of BG and QY dyes to activated carbon proceeded. Gibbs free energy was found that the adsorption reaction became more spontaneous with increasing temperature. As a result of competitive adsorption of the mixed solution, it was found that QY was disturbed by BG and the adsorption reduced.

• Membrane Journal
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• v.17 no.3
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• pp.219-232
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• 2007

The polyethersulfone(PES)-titanium oxide($TiO_2$) hybrid membranes were prepared by immersion precipitation phase inversion method. The casting solution for the preparation of $PES-TiO_2$ hybrid membrane was provided by adding $TiO_2$ nano particles into the basis polymer solution of 14 wt% and 20 wt% PES/N-methyl-2-pyrrolidone(NMP). The $TiO_2$ loading [wt% ($TiO_2/NMP$)] in eating solution was varied from 0 to 60 wt%. Membrane performance and morphological change of the resulting $PES-TiO_2$ hybrid membranes were discussed in aspect of $TiO_2$ loading, by viscosity, coagulation value and light transmittance of the casting solution, measurement of tensile strength, pore size and contact angle, surface and cross sectional SEM images of the hybrid membrane, and ultrafiltration experiments using the hybrid membrane. According as increase of $TiO_2$ loading in the casting solution, viscosity is increased and coagulation value becomes lower, therefore the thermodynamic instability of the casting solution is increased. It is found that when $TiO_2$ loading is increased, 1) precipitation rate becomes faster while instantaneous demixing is maintained, 2) pure water flux, membrane pore size and compaction stability of the resulting membranes are increased, 3) tensile strength and contact angle are decreased. Dead-end ultrafiltration of bovine serum albumin(BSA) solution using the hybrid membrane shows that membrane performance(flux of BSA solution) enhanced up to 7 times compared with the results obtained using the pure PES membrane(not containing $TiO_2$ particle), due to the increase of hydrophilicity.

• Journal of the Korean Chemical Society
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• v.42 no.5
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• pp.512-518
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• 1998

In this study, various thermodynamic and hydrodynamic parameters characterizing the solution properties of polyethylene ionomer particles in water were determined at $30^{\circ}C$ by means of light scattering and viscosity measurements. Based on the experimental data, we investigated the solution behavior of three kinds of polyethylene ionomers, which are different in composition of the pendant ionic groups of COOK, COOH and $CONH_{2}$, and characterized their particle properties. Ionomers containing 7.6 mol% potassium salt only behave as flexible coils in a relatively good solvent state. On the other hand, two ionomers containing 3.8 mol% amide group together with potassium salt form the compact particles. In addition, the concentration dependence of the effective diffusion coefficient $(D_{eff})$ and the reduced viscosity of the latter ionomers showed the opposite trend from the former, indicating that the composition of the pendant ionic groups have a great influence on the interparticle interaction of ionomers formed in water.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.23-29
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• 2003

Setschenow constants of six alkali and alkaline earth metal-based electrolytes (i.e., NaCl, KCl, CaCl$_2$, K$_2$SO$_4$, Na$_2$SO$_4$, NaClO$_4$) for three polycyclic aromatic hydrocarbons (PAHs) (i.e., naphthalene, pyrene, and perylene) were investigated to evaluate the influence of a variety of inorganic salts on the aqueous solubility of PAHs. Inorganic salts showed a wide range of K$\_$s/ values (L/mol), ranging from 0.1108 (NaClO$_4$) to 0.6680 (Na$_2$SO$_4$) for naphthalene, 0.1071 (NaClO$_4$) to 0.7355 (Na$_2$SO$_4$) for pyrene, and 0.1526 (NaClO$_4$) to 0.8136 (Na$_2$SO$_4$) for perylene. In general, the salting out effect of metal cations decreased in the order of Ca$\^$2+/>Na$\^$+/>K$\^$+/. The effect of SO$_4$$\^$2-/>Cl$\^$-/>ClO4$\^$-/ was observed for anions of inorganic salts. The K$\_$s/ values decreased in the order of perylene>pyrene>naphthalene for K$_2$SO$_4$. However, the order of decreasing salting out effect for NaCl, KCl, CaCl$_2$, and NaClO$_4$ was perylene>naphthalene>pyrene. Hydration free energy of the 1:1 and 2:1 alkali and alkaline earth metal-based inorganic salts solution was observed to have a meaningful correlation with Setschenow constants. Thermodynamic interactions between PAH molecules and salt solution can be of importance in determining the magnitude of salting out effect for PAHs at a given salt solution.

• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.127-138
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• 1994

In the process of pervaporation separation for aqueous ethanol solution through cellulose tai-acetate(CTA) membrane, the modelling on the solution-diffusion permeation mechanism was built up on the basis of sorption and permeation experimental results. Also its function type and parameter were examined. The composition of sorption equilibrium in three component system(Ethanol/Water/CTA) were compared with the calculated value by Flory-Huggins' equation using the pure component sorption data. In order to apply the thermodynamic equilibrium relationship between the membrane free composition in the membrane and the equilibrium composition in the liquid phase, the apparent activity this system, however, the results were not satisfied. Diffusion equations were expressed with the concentration gradient considering permeate alone, and a concentration-dependent diffusion coefficient which includes a parameter was used. And this model was fitted with the measured permeation rates. If the permeation rate and the amount of sorption of one component were much larger than those of the other, the bulk flow term could not be negligible. The flux and selectivity were increased with increasing temperature, and with decreasing downstream pressure.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.277-290
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• 1993

Dental caries is considered to be caused by demineralization by organic acid produced by microorganism. But the formation of subsurface lesion in initial caries make it diffcult to explain by simple demineralization. This study is carried out on the basis of thermodynamic concept proposed by Margolis and Moreno. The purpose of this study is to evaluate the effects of acid concentration and pH of lactate buffer system on the artificial caries lesion progress. 160 teeth without any crack, defect or opaque enamel were used and coated with nail varnish except the window ($2{\times}3$ mm). Under the constant degree of saturation(D.S.). The teeth were divided into 8 groups according to acid concentration(10mM, 25mM, 50mM, 100mM) and pH(4.3, 5.0, 6.0). Each group was immersed in buffer solution for 3, 6, 9, 18 days under controlled temperature($25^{\circ}C$). After cutting through the window and grinding, the specimens, 100-150 um in thickness, were imbibed in water or air and examined using polarilizing microscope. The depth of the surface and subsurface surface lesion were measured. 1. In the constant pH and D. S. value, the subsurface lesion progresses more rapidly as the concentration of lactic acid increases. (0.01, 0.025, 0.05, 0.1) 2. In the constant acid concentration and DS value, the subsurface lesion progresses more slowly as the pH increases. (4.3, 5.0, 5.5, 6.0) 3. The width of surface lesion seems to be constant independant of pH and acid concentration.

• Journal of the Korean Chemical Society
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• v.39 no.6
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• pp.440-445
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• 1995

The chemical compositions and stability constants, thermodynamic parameters for the neodymium(Ⅲ) complexes of substituted benzo-1,4,7,10,13-pentaoxacyclopentadecane(B15C5) have been determined by spectrophotometry and conductometry in methanol solution at various temperatures. As substituents, CH3, Br, CHO, NO2, and 3,4-(NO2)2 were used. In methanol solution the ratios of neodymium(Ⅲ) to the ligands in the complexes are 1 : 1. The stability constants were increased in order of B15C5-3,4-(NO2)2 < B15C5-NO2 < B15C5-CHO < B15C5-Br < B15C5 < B15C5-CH3. This observation can be explained in terms of the substituent effect. The order of stability constants was dimethylsulfoxide < acetone < acetonitrile in solution and the magnitudes were found to be inversely proportional to the solvents donicities. These results could be understood in terms of solvent basicity, ligand basicity, solvation of the cation, and entropy changes of complex formation.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.556-560
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• 2009

Aggregation behavior of three kinds of benzindocarbocyanine dyes in aqueous methanol solution was studied by UV-Vis absorption spectrum. The results indicated that the three dyes all existed monomer-dimer equilibrium in aqueous methanol solution (concentration range $10^{−5}\;to\;10^{−6}$ M) at 25.0$\sim$41.0 ${^{\circ}C}$ for Dye 1, 28.0$\sim$49.0 ${^{\circ}C}$ for Dye 2 and 26.0$\sim$47.0 ${^{\circ}C}$ for Dye 3. The fundamental property of the three dyes as the dimeric association constant KD, the dimeric free energy ${\Delta$}G_D, the dimeric entropy ${\Delta$}S_D, and the dimeric enthalpy ${\Delta$}H_D were determined. The ${\Delta$}H_D of three dyes: Dye 1, Dye 2 and Dye 3 was -42.5, -15.1 and -18.9 kJ/mol, respectively. The experimental observations were the subject of a theoretical study including the ground-state geometries which were fully optimized using DFT at B3LYP/6-31G level. The effect of dye molecule structure on ${\Delta$}H_D was discussed by theoretical calculations.

• Journal of Navigation and Port Research
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• v.37 no.2
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• pp.129-135
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• 2013

Recently, waste water treatment system is developed in small and middle size to get more economic advantage. Freeze concentration system has high thermodynamic efficiency and low energy consumption, can re-use purified water and cold energy obtained from ice. This study was experimentally performed to investigate pollution containment in frozen layer by cooling wall temperature, air-bubble flow methods, initial ice-lining thickness of frozen layer in NaCl aqueous solution and the representative heavy metals, Pb and Cr aqueous solution. As the result, a decrease in the cooling wall temperature bring a higher growth rate of ice front and the more solute was involved in frozen layer. The method to inject directly air-bubble into ice-liquid interface through ring shape nozzle gave high purity of ice compared to indirect method. Ice lining in 5mm thickness resulted in frozen layer with higher purity than 1mm thickness.

• Atmosphere
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• v.32 no.3
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• pp.235-246
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• 2022

A large number of MJO skill metrics and process-oriented MJO simulation metrics have been developed by previous studies including the MJO Working Group and Task Force. To assess models' successes and shortcomings in the MJO simulation, a standardized set of diagnostics with the additional set of dynamics-oriented diagnostics are applied. The Global Coupled (GC) model developed for the operation of the climate prediction system is used with the comparison between the GC2 and GC3.1. Two GC models successfully capture three-dimensional dynamic and thermodynamic structure as well as coherent eastward propagation from the reference regions of the Indian Ocean and the western Pacific. The low-level moisture convergence (LLMC) ahead of the MJO deep convection, the low-level westerly and easterly associated with the coupled Rossby-Kelvin wave and the upper-level divergence are simulated successfully. The GC3.1 model simulates a better three-dimensional structure of MJO and thus reproduces more realistic eastward propagation. In GC2, the MJO convection following the LLMC near and east of the Maritime Continent is much weaker than observation and has an asymmetric distribution of both low and upper-level circulation anomalies. The common shortcomings of GC2 and GC3.1 are revealed in the shorter MJO periods and relatively weak LLMC as well as convective activity over the western Indian Ocean.