• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.4
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• pp.190-195
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• 2002

NaX zeolite crystals of a uniform particle size of 50 $\mu$m were grown by continuous crystallization method from seed crystals (10~20 $\mu$m) added into a 0.5~2.0 g mother liquor having a composition $3.5Na_2O : Al_2O_3: 2.1SiO_2: 1000H_2O$. In order to investigate the crystal growing by continuous method, the mother solution was supplied after 7 days, 5 days, 3 days and 1 day, respectively. The seeding resulted in an increase in the fraction of large crystals compared with unseeded batches and successfully led to an uniform NaX zeolite crystal. It was postulated that the seeding in the synthesis mixture leaded out increase of surface area for physical contact reaction and directed growth of seed crystal without the nucleation in the synthesis gel.

• Clean Technology
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• v.7 no.1
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• pp.51-63
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• 2001

In this study, PSA, known as the most economic process, was used to recover $CO_2$ from the power-plant flue gas. Activated carbon and zeolite molecular sieve 13X were used as adsorbent. Activated carbon has been deemed inadequated adsorbent for separating $CO_2$ from the flue gas. However, highly concentrated $CO_2$ could be obtained as a product on the activated carbon adsorbent using the new operating cycle modifying the rinse step. Also, the recovery of $CO_2$ was improved using double-layered adsorption column packed with the activated carbon and the zeolite 13X simultaneously. Adsorption column was filled with the activated carbon in the feed-end side, and the zeolite 13X in the product-end side. The recovery of $CO_2$ increased about 40% with only 25% zeolite, and increased 67% with 50% zeolite at the experimental conditions of 13% $CO_2$ concentration, 10 SLPM flow rate and 2.2 atm adsorption pressure.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.201-209
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• 2006

Various desorption methods were investigated for an activated carbon and zeolite 13X packed bed after benzene adsorption. Desorption experiments using hot steam, purge gas, and evacuation were performed. As a result, the desorption with hot steam showed the best performance. Hot steam makes the temperature in the adsorption column increase and gives arise to the desorption. Drying process should be accompanied to increase the efficiency because steam vapor prevents the adsorption later. The vacuum desorption showed poor performance and it reveals that temperature swing operation is more effective than pressure swing operation. In the purge gas desorption, good performance was achieved using evacuation.

• Applied Chemistry for Engineering
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• v.4 no.4
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• pp.731-738
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• 1993

This study showed the adsorption behavior of Cs and Sr into the inorganic ion-exchanger zeolites such as 4A, 13X, AW300, AW500 and natural. It was found that the best type of zeolite is AW500 for Cs and 13X for Sr in terms of ion-exchange capacity. The temperature effect was also examined for the following systems : AW500-Cs, AW300-Cs, natural zeolite-Cs, 4A-Sr and 13X-Sr. Experiments showed that the effect of temperature on the ion-exchange capacity is negligible in all cases except for the systems of 4A-Sr and natural zeolite-Cs. The enhancement in the ion-exchange capacity for 4A-Sr would be caused by the Sr ion movement and the multilayer adsorption due to the heterogeneous characteristics of ion-exchange site. The distribution coefficient was increased with pH of the solution which is in equilibrium with zeolite particles. The values of $K_d$ in the systems of AW500-Cs and 4A-Sr were found to be about $10^3cm^3/g$ and $10^3{\sim}10^4cm^3/g$ respectively.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.726-730
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• 2019

The removal of calcium ions using zeolite to solve problems of the CaCO₃ manufacturing process using cement kiln dust was investigated. To do so, a modified zeolite was employed and experiments were conducted to select the optimal zeolite type considered the binding cation and structure, evaluate the removal performance of calcium ions, the influence of the type and concentration of the modifying solution, and the removal selectivity when K coexists. Among five zeolites, 13X zeolite was found to have the best calcium ion removal performance, and it was confirmed that the removal performance was enhanced when KCl was used as a modifying solution instead of NaCl. This study is expected to be the basis for the solution of carbonation process and high concentration of KCl recovery technology.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1121-1126
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• 2002

Two anhydrous crystal structures of fully dehydrated Cd2+ - and Cs+ -exchanged zeolite X, Cd32Cs28Si100Al92O384 (Cd32Cs28-X: a = 24.828(11) $\AA)$ and fully dehydrated Cd,sup>2+ - and Rb+ -exchanged zeolite X, Cd28Rb36Si100Al92O384 (Cd28Rb36-X: a = 24.794(2) $\AA$), have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at $21(1)^{\circ}C.$ The structures were refined to the final error indices, R1 = 0.058 and R2 = 0.065 with 637 reflections for Cd32Cs28-X and R1 = 0.086 and R2 = 0.113 with 521 reflections for Cd28Rb36-X for which I > $3\sigma(I)$. In the structure of Cd,sub>32Cs28-X, 16 Cd2+ ions fill the octahedral sites I at the centers of the double six rings (Cd-O = $2.358(8)\AA$ and O-Cd-O = $90.8(3)^{\circ}$ ). The remaining 16 Cd2+ ions occupy site II (Cd-O = $2.194(8)\AA$ and O-Cd-O = $119.7(4)^{\circ})$ and six Cs+ ions occupy site II opposite to the single six-rings in the supercage; each is $2.322\AA$ from the plane of three oxygens (Cs-O = 3.193(13) and O-Cs-O = $73.0(2)^{\circ}).$ Aboutten Cs+ ions are found at site II', $1.974\AA$ into the sodalite cavity from their three oxygen plane (Cs-O = $2.947(8)\AA$ and O-Cs-O = $80.2(3)^{\circ}).$ The remaining 12 Cs+ ions are distributed over site III' (Cs-O = 3.143(9) and O-Cs-O= $59.1(2)^{\circ})$. In the structure of Cd28Rb36-X, 16 Cd2+ ions fill the octahedral sites I at the center of the double-sixrings (Cd-O = 2.349(15) and O-Cd-O = $91.3(5)^{\circ}$ ). Another 12 Cd2+ ions occupy two different II sites (Cd-O = $2.171(18)/2.269(17)\AA$ and O-Cd-O = $119.7(7)/113.2(7)^{\circ}).$ Fifteen Rb+ ions occupy site II (Rb-O = $2.707(17)\AA$ and O-Rb-O = $87.8(5)^{\circ}).$ The remaining 21 Rb+ ions are distributed over site III' (Rb-O = $3.001(16)\AA$ and O-Rb-O = $60.7(4)^{\circ})$. It appears that the smaller and more highly charged Cd2+ ions prefer sites I and Ⅱ in that order, and the larger Rb+ and Cs+ ions, which are less able to balance the anionic charge of the zeolite framework, occupy sites II and II' with the remainder going to the least suitable site in the structure, site III'.The maximum Cs+ and Rb+ ion exchanges were 30% and 39%, respectively. Because these cations are too largeto enter the small cavities and their charge distributions may be unfavorable, cation-sieve effects might appear.

• 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.

• Bulletin of the Korean Chemical Society
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• v.21 no.2
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• pp.180-186
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• 2000

• Analytical Science and Technology
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• v.13 no.3
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• pp.394-398
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• 2000

The mineralogical properties of natural zeolite comixed with montmorillonite were investigated by the chemical composition analysis, X-ray diffraction analysis, and differential scanning calorimetry. The experimental results on the removal of heavy metal ions by using the natural sample are summerized as follows. The removal of the heavy metal in solution is greatly influenced by the pH. Also, the removal capacity of heavy metal ions by zeolite and montmorillonite have increased in order of $Cu^{2+}>Cd^{2+}>Ni^{2+}$.

• Journal of Environmental Science International
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• v.20 no.6
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• pp.729-736
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• 2011

This work is to compare the experiment results by a continuous fixed-bed adsorption of water vapor, acetone vapor, and toluene vapor on zeolite 13X (SAU) and silica-alumina (SAK). SAU and SAK have very different pore structure but similar composition as inorganic adsorbent. The relationship between the equilibrium adsorption capacity and specific pore size range were studied. Adsorption of water vapor was more suitable on SAU than SAK because SAU has relatively more developed pores around $5\;\AA$ than SAK in the pore range of $10\sim100\;\AA$. Adsorption of acetone vapor was more suitable on SAK than SAU because SAK has relatively more developed pores around $5\sim10\;\AA$ than SAK in the pore range of less than $10\;\AA$. Adsorption of toluene vapor was more suitable on SAK than SAU because SAK has relatively more developed pores in the pore range of $10\sim100\;\AA$ than SAK. Adsorption capacity of the adsorbent was closely related to the surface area generated in the specific pore size region. But it was difficult to distinguish the relationships between adsorption capacity and micro area, and the external surface area of adsorbent.