• Economic and Environmental Geology
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• v.34 no.2
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• pp.167-173
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• 2001

Through alkaline hydrothermal activation processes, Na-A type zeolite was synthesized as a single phase with funnel-glass waste from a television tube factory. The autoclaving was performed in a closed teflon vessel in the range of 80~95$^{\circ}$C. The silica-rich solution as a starting material was hydrothermally synthesized with quartz in IN NaOH by heating 350uC under the pressure of 1,500 atm. $NaAlO_2$ was made from NaOH and Al(OHh by heating 95$^{\circ}$C for 2-3 hours and the molar ratios of it were $Na_2O/Al_2O_3$ = 1.4 and $H_2O/Na_2O$=8. The equi-dimensional A type zeolite (1-2 11) was formed by the simple mixing of the silica-rich solution, glass waste and $NaAlO_23$ for 1-3 hours-heating at $80^{\circ}C$. The characterization of the reaction product shows Na-A as a single phase. The synthesized zeolite has cuba-dodecahedral form and $Ca^{2+}$ ion exchange capacity of the Na-A was in the range of 215-220 mequiva1entilOO g.

• 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 the Mineralogical Society of Korea
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• v.5 no.2
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• pp.61-71
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• 1992

Through the low-temperature(60-150${\circ}C$) hydrothermal treatment of perlite with the alkaline solution at various NaOH concentrations, the mode of volcanic glass alteration and resultant zeolite formation were investigated in a closed system. At a temperature of 80${\circ}C$ and alkalinities of pH range 8 to 12, corresponding to the natural environments of diagenetic zeolite formation, only weak dissolution of perlitic glass occurs without zeolite formation despite the residence time of 100 days. Activities of Si and Al increase progressively, as a consequence of increasing pH, whereas activity ratios of Si/Al decrease. Zeolites were synthesized from perlite in the alkaline solution at above 0.1M NaOH concentrations. Below the temperature of 100${\circ}C$ Na-P was mainly formed, whereas analcime was the dominant zeolite at the temperature range of 100-150${\circ}C$. During Na-P synthesis chabazite and Na-X were also formed as by-products in case of lower proportion of solution/sample(<10ml/g) and higher NaOH concentraion (>3M), respectively. The alteration modes of perlite in the zeolite synthesis reflect that the formation of synthetic zeolites occurs as an incongruent dissolution likely with the diagenetic formation of natural zeolites from volcanic glass. Considering much difference in reaction kinetics between natural and synthetic systems, however, the evaluated synthetic conditions in these experiments were not directly applicable to the natural diagenetic system.

• 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 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.

• Membrane Journal
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• v.18 no.3
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• pp.250-255
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• 2008

Zeolite A have been known to be chemically, mechanically and thermally quite stable. The ion-exchanged membranes were tested for the removal of water from ethanol/water mixtures by pervaporation. Since it is quite difficult to prepare the potassium form of zeolite A by a direct synthesis, it was obtained by the ion-exchange method from NaA zeolite. The effects of concentration of ethanol at the feed side and the temperature were studied on the permeation flux and the separation factor of water. After $Na^+$ ion was exchanged to $K^+$ ion, it was found that the total flux decreased and the separation factor increased.

• 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.

• Korean Journal of Crystallography
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• v.12 no.2
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• pp.97-101
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• 2001

Phillipsite-type zeolite powders were synthesized from domestic coal fly ash by hydrothermal reaction with 2.0 M-3.5M NaOH solution at $80^{\circ}C{\sim}120^{\circ}C$ for 24 h. The properties of zeolite were investigated by XRD, SEM and IR spectroscopy. The effects of chemical composition of fly ash, reaction temperature and NaOH concentration on the zeolite synthesis were well appeared on IR spectra. It is found that the $TO_4$(T=Si, Al) tetrahedra have a well ordered structure as the $SiO_2$ content, synthesis temperature and NaOH concentration become high.

• 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.34 no.6
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• pp.1693-1697
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• 2013

This study develops a novel method to remove the free cations created during the synthesis of ionic liquid. The cations are removed from the ionic liquid by size-selective adsorption onto chemically surface-modified Zeolite. The porous crystal nano-structure of Zeolite has several electron-rich Al sites to attract cations. While large cations of an ionic liquid cannot access the Zeolite nano-structure, small cations like $Na^+$ have ready access and are adsorbed. This study confirms that: $Na^+$ can be removed from ionic liquid effectively using Zeolite; and, in contrast to the conventional and extensively applied ion exchange resin method or solvent extraction methods, this can be done without changing the nature of the ionic liquid.