• Membrane Journal
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• v.19 no.3
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• pp.189-193
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• 2009

The present work was attempted to improve the performance for the removal of water from ethanol/water mixtures through the ion-exchanged zeolite membrane in which $Na^{+}$ ion was substituted to either $K^{+}$ or $Ca^{2+}$ ion. The membranes were ion-exchanged with 0.5 mole/L aqueous solution of either KCl or $CaCl_2$ at $80^{\circ}C$ for 4 hrs. In case of the ion-exchanged membrane in which $Na^{+}$ ion was substituted to $K^{+}$ ion, the total flux was decreased from $900\;g/m^2{\cdot}hr{\sim}2,500\;g/m^2{\cdot}hr$ to $600\;g/m^2{\cdot}hr{\sim}2,000\;g/m^2{\cdot}hr$ and the separation factor was increased from $600{\sim}2,200$ to $850{\sim}2,500$ compared to the NaA type zeolite membrane. And in case of the ion-exchanged membrane in which $Na^{+}$ ion is substituted to $Ca^{2+}$ ion, both the total flux and selectivity of water showed the similar tendency compared to the NaA type zeolite membrane. It is thought that the improved separation would be possible if the pore size of the zeolite membrane is controlled by the ion exchange.

• Journal of the Korean Chemical Society
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• v.23 no.6
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• pp.374-384
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• 1979

Hydration scheme and hydration energy are determined in ${\alpha}$ cage of zeolite NaA. The selectivity between Na(1) and Na(2) is determined from energy calculation. The waters in ${\alpha}$ cage form a distorted dodecahedral cage. The average binding energies of water(1), water(2) and water(3) are -29.847, -25.344 and -15.888 kcal/mole respectively. The positions of oxygens of hydrated waters are in good agreement with the X-ray data. The heat of immersion curve is also obtained. This result is in good agreement with the differential heat of sorption curve obtained from differential thermal analysis. It is concluded that theoretical method provides considerable uses in the determination and understanding of the hydration and interaction energy of zeolites sorbate binding.

• Journal of Environmental Science International
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• v.28 no.6
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• pp.561-570
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• 2019

A zeolitic material (Z-Y2) was synthesized from Coal Fly Ash (CFA) using a fusion/hydrothermal method under low-alkali condition (NaOH/CFA = 0.6). The adsorption performance of the prepared zeolite was evaluated by monitoring its removal efficiencies for Sr and Cs ions, which are well-known as significant radionuclides in liquid radioactive waste. The XRD (X-ray diffraction) patterns of the synthesized Z-Y2 indicated that a Na-A type zeolite was formed from raw coal fly ash. The SEM (scanning electron microscope) images also showed that a cubic crystal structure of size $1{\sim}3{\mu}m$ was formed on its surface. In the adsorption kinetic analysis, the adsorption of Sr and Cs ions on Z-Y2 fitted the pseudo-second-order kinetic model well, instead of the pseudo-first-order kinetic model. The second-order kinetic rate constant ($k_2$) was determined to be $0.0614g/mmol{\cdot}min$ for Sr and $1.8172g/mmol{\cdot}min$ for Cs. The adsorption equilibria of Sr and Cs ions on Z-Y2 were fitted successfully by Langmuir model. The maximum adsorption capacity ($q_m$) of Sr and Cs was calculated as 1.6846 mmol/g and 1.2055 mmol/g, respectively. The maximum desorption capacity ($q_{dm}$) of the Na ions estimated via the Langmuir desorption model was 2.4196 mmol/g for Sr and 2.1870 mmol/g for Cs. The molar ratio of the desorption/adsorption capacity ($q_{dm}/q_m$) was determined to be 1.44 for Na/Sr and 1.81 for Na/Cs, indicating that the amounts of desorbed Na ions and adsorbed Sr and Cs ions did not yield an equimolar ratio when using Z-Y2.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.43.1-43
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• 2003

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.3
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• pp.240-246
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• 1985

This study was conducted to estimate the proper particle size of Zeolite particle as the soil conditioner for sandy soil. On sand columns filled with different size of sand fractions, Zeolite particles of different size were applied. Tap water was percolated through those columns under the same water level as paddy soil during rice growth. The > 0.1mm fraction of Zeolite was not vertically moved although the water was percolated for 96 hours. The < 0.1mm fraction of Zeolite was moved out 85.7% in 2-1mm, 32.64% in 1-0.5mm, and 24.5% in 0.5-0.25mm sand column, respectively. The proper diameter of Zeolite particle for amelioration of sandy soils widely distributed around river side in Korea was estimated as 0.25-0.1mm fraction in consideration of its pore size.

• Journal of the Korean Geophysical Society
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• v.4 no.4
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• pp.251-256
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• 2001

Korean natura1 zeolite with fe1dspar and illite as impurities was purified by an air c1assification method. X-ray powder diffraction ana1yses showed that the air c1assification effectively separated zeolite and impurities, and reduce the amount of impurity of the natura1 zeolite. The zeolite with air c1assification was treated with 1N NaOH solutions at temperatures at 100, 150, 200 ℃ for 17hours. The obtained hydrotherma1 treatment of phase change to philli1site and ana1cime from mordenite and clinopti10lite.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.339-349
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• 2015

In this work, DAY (Dealuminated Y-type) zeolites were prepared to be used as easily regenerable and thermally stable adsorbent substituting activated carbon. NaY zeolites were transformed into DAY zeolites through ion exchange, calcination, steaming, and acid leaching. Calcination temperature and time, and steaming time were changed to increase the Si/Al ratio and maintain crystallinity. Adsorption of VOCs were done for prepared DAY, commercial NaY and Hisiv 1000 in air with relative humidity of 50%. The DAY zeolite prepared by calcination at $520^{\circ}C$ for 4 hrs and steaming for 7 hrs had a same structure and a Si/Al ratio of 80.4. Its adsorption capacity for water vapor was 10% of NaY, indicating its hydrophobicity. Its adsorption capacity for MEK was 0.8 times of Hisiv 1000, that for toluene 1.6 times, and that for EA 1.3 times.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.11a
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• pp.25-28
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• 2003

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.5
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• pp.204-210
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• 2004

Though the recycling rate of coal fly ash generated from domestic thermoelectric power plants is gradually increased, at present, the most amount of coal bottom ash is disposed by a landfill instead of recycling. Therefore, to reuse a coal bottom ash as high-value materials the synthesis of zeolite made from a coal bottom ash was investigated in this study. NaPl, hydroxy-sodalite and tobermorite were produced through the alkaline hydrothermal reaction of pulvelized bottom ash at various temperatures; 80, 120, $150^{\circ}C$, and the concentration of NaOH at the range from 1 to 5 M. Especially, NaPl with excellent cation exchange capability had a high crystallinity at ${\leq}2$ M NaOH and ${\leq}120^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.13 no.3
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• pp.317-324
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• 1992

Structure and dynamics of $Na^+$ ions are investigated by molecular dynamics simulations of rigid dehydrated zeolite-A at several temperatures using a simple Lennard-Jones potential plus Coulomb potential. A best-fitted set of electrostatic charges is chosen from the results of simulation at 298.15 K and Ewald summation technique is used for the long-ranged character of Coulomb interaction. The calculated x, y, and z coordinates of $Na^+$ ions are in good agreement with the positions determined by X-ray crystallography within statistical errors, their random movings in different types of closed cages are well described by time-correlation functions, and $Na_Ⅰ$ type ions are found to be less diffusive than $Na_Ⅱ$ and $Na_{III}$. At 600.0 K, the unstable $Na_{III}$ type ion pushes down one of nearest $Na_{I}$ ions into the $\beta-cage$ and sits on the stable site Ⅰ, and the captured ion in the $\beta-cage$ wanders over and attacks one of 8 $Na_{I}$ type ions.