• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.98-105
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• 2013

The NaA zeolite particles were dispersed in a poly(vinyl alcohol) (PVA) matrix to prepare a composite membrane. The nano sized zeolite particles of NaA were synthesized in the laboratory and the mean size was approximately 60 nm. Pervaporation characteristics such as a permeation flux and a separation factor were investigated using the membrane as a function of the feed concentration from 0.01 to 0.05 mole fraction and the weight % of NaA particles between 0 wt% and 5 wt% in the membrane. Also, the micro sized particles of $5{\mu}m$ were dispersed in the membrane for a comparison purpose. When the ethanol concentration in the feed solution was 0.01 mole fraction, the flux of water significantly increased from $600g/m^2/hr$ to $2000g/m^2/hr$ as the content of the nano NaA particles in the membrane increased from 0 wt% to 5 wt%, while the NaA particles improved the separation factor from 1.5 to 7.9. When the flux of water through the membrane containing nano sized particles was roughly 15% increased compared to the micro sized particles, whereas the separation factor of water was found to be approximately 5% increased. It can be said that the role of the nano sized NaA particles is quite important since both the flux and the separation factor are strongly affected.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.3
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• pp.95-101
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• 2007

The synthesis of NaA zeolite membrane on a porous alumina support from clear solution by using hydrothermal reaction was investigated. Effects of reaction temperature, reaction time and seeding for transformation of zeolite A membrane and powder which are produced in the reactor were monitored through X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The transformation process of producing Zeolite A membrane starts from the formation of the compact and continuous membrane on the surface of porous support from clear solution. The large Zeolite A poly-crystal was then farmed through the dissolution process. Finally, the process was advanced from sodalite to amorphous. In case of powder, sodalite is formed in the early stage of reaction because of surrounding space difference between membrane and powder crystal. Discrete surrounding space of powder crystal makes easy to transform to sodalite. From Zeolite A to amorphous through transformed product was rapidly advanced at high temperature while the membrane with somewhat low coverage was obtained at low temperature. A compact and continuous zeolite A membrane was synthesized at $120^{\circ}C$ in 12-hour period.

• The Journal of Natural Sciences
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• v.6 no.1
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• pp.103-108
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• 1993

Zeolites were discovered as a natural mineral more than two hundred ago. In the beginning, the mineral was used as ion-exchange material and adsorbent. After the end of World War II , however, a variety of zeolites have become available in large amounts because of the establishment of low temperature synthesis and the discobery of natural zeolite deposits of sedimentary origin. Various uses of xeolite were developed utilizing the unique crystal strucrure and function of these minerals. In connection with this development remakable progress has also been made in basic stuides on the related geology and mineralogy, crystallization from sols and gels, structure, ion exchange, adsorption and cataiysis. As a result, zeolites, which had been known only as mineral specimens displayed in museums. established a firm position among the high-technology masterials with excellent functional capabilities.

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.600-606
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• 2018

The influence of acidity in MTT zeolite of different Si/Al molar ratio's on the catalyst activity in methanol-to-olefin (MTO) reaction has been investigated. The Si/Al ratio was controlled with the Al content in the gel when N,N,N',N'-tetramethyl-1,3-diaminopropane was used as a structure directing agent (SDA). The gel composition was controlled to $20SiO_2$ : 30SDA : x (=0.25~1.25)$NaAlO_2$ : 2NaOH : $624H_2O$, which was subject to the hydrothermal synthesis at 433 K for 4 days. As the composition of sodium aluminate decreased, the particle size of MTT zeolite increased, and also the amount of acid sites decreased. To investigate the catalytic performance, MTO reaction was carried out at 673 K with $1.2h^{-1}$ WHSV. It was found that the H-MTT (1.00Al) catalyst with a Si/Al molar ratio of 24 maintained the methanol conversion over 90% for 900 min.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.9
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• pp.505-512
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• 2017

The adsorption characteristics of Sr ion in aqueous solution was examined using zeolite NaA powder (Z-PA) and pellets (Z-BA). In batch experiment, the adsorption of Sr ions by Z-BA and Z-PA was well expressed by pseudo-second-order kinetic model than psedo-first-order kinetic model. Experimental isotherm results was well fitted to Langmuir isotherm model and the maximum adsorption capacities obtained from Langmuir isotherm model were 233.32 mg/g for Z-PA and 164.60 mg/g for Z-BA, respectively. The continuous experiment results showed that the total Sr ion uptake (q) increased, but the breakthrough time, effluent volume ($V_{eff}$) and total removal (R) of Sr ion decreased with the Sr ion concentration. The breakthrough curves obtained from the experiment was modeled by Thomas model.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.137-146
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• 1992

The adsorption properties of CO on the cation exchanged natural zeolite, $K_{111}$ and cation effects upon the CO adsorption were studied. $Na^+-,\;Cu^{2+}-\;and\;Ba^{2+}-\;K_{111}$ exhibited relatively good CO adsorption capacities and $Ba^{2+}- K_{111}$ treated by 0.4 N-$BaCl_2$ solution proved itself as the best adsorbent and superior to the synthetic zeolite 4A and 5A. The observed adsorption tendency due to the cations were in the order of $Ba^{2+}>Cu^{2+}>Na^+>K^+>Mg^{2+}>Ca^{2+}$. The cation exchanged number per unit cell as well as the kind of cation which forms bond with CO molecules in different intensities and other mineral factors such as pore size indicated to be important factors to the CO adsorption properties. The CNDO/2 calculations were performed to compare the adsorption tendencies and CO interaction energy of cations in $K_{111}$.

• Journal of the Mineralogical Society of Korea
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• v.10 no.2
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• pp.105-113
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• 1997

Mineral description and mineralogical characterization were made for the wellsite, a barrian zeolite, which found as diagenetic alterations in the Miocene pyroclastic rocks in Gampo area. The wellsite occurs together with clinoptilolite, smectite and apatite as euhedral crystallites (0.2~0.4mm) forming interpenetraion twinning in the vesicles of altered pmice fragments. Compared to other reported wellsites, the wellsite is rather silicic (Si/(Al+Fe): 3.12-3.16) and Ca-rich. Unit cell dimensions and chemical formular determined from XRD, EMPA and TGA data are as follows:a=9.883$\AA$, b=14.204$\AA$, c=8.677$\AA$, $\beta$-124.764$^{\circ}$, (Ba0.57K0.36)(Ca1.18Na0.04)Al3.9Si12.1O32.13.9H2O.The cation composition of the Gampo wellsite, which shows an exchange reaction in the form of Ba2++Ca2+=2(K++Na-), is deviated far from the compositional range of a phillipsite-harmotome series. Due to higher abundance of divalent cations (Ca, Ba) and si in the wellsite, cimpared to those of the phillipsite and harmotome reported in other areas, the zeolite seems to be characteristic of higher water content (18.7 wt%) and higher thermal stability. XRD, chemical and thermo-chemical results of the wellsite reflects that wellsite is rather a Ba- and Ca-rich end member of a phillipsite-harmotome-wellsite series than an intermediate phase of phillipsite-harmotome series or a barrian variety of phillipste.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.1
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• pp.14-19
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• 2001

The crystal size was determined as a function of reaction temperature, during the crystallization process of NaX zeolite. The measured rate constants for linear growth were as 0.0441$\mu\textrm{m}$/h at $80^{\circ}C$, 0.0595$\mu\textrm{m}$/h at $90^{\circ}C$ and 0.0972$\mu\textrm{m}$/h at $100^{\circ}C$, respectively. The activation energy calculated from the relation between the linear growth rate an the reaction temperature was 43.243kJ/mol. The reaction of crystal growth were revealed as 20 days at $80^{\circ}C$, 16 days at $90^{\circ}C$ and 9 days at $100^{\circ}C$, respectively. Both the final product crystal size an the crystallization time were decreased with increasing reaction temperature.

• Food Science and Preservation
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• v.11 no.4
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• pp.478-484
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• 2004

Freshness maintenance of polyethylene packaging film containing surface-modified zeolite was investigated depending on the nature of substituted cations and cationic surfactants. Freshness maintenance was designed to work by cation or cationic surfactant adsorbed onto the zeolite surface by ion-exchange method. Cationic surfactants such as DODAB (n-dodecyltrimethylammonium bromide), CTAB (n-cetyltrimethylammonium bromide), and DHAB (n-dihexadecyldime-thylammonium bromide), and cations ($Ce^{3+},\;Al^{3+},\;Mg^{2+},\;Ca^{2+},\;Ag^{3+},\;Na^{1+}\;and\;Cu^{3+}$) were used. Surface-modified zeolite powder was compounded with LDPE to produce $20\;wt\%$ zeolite masterbatch (M/B), and the M/B was again blended with LDPE to get zeolite-containing LDPE films with 3, 5, $10\;wt\%$ of zeolite (width: 40 cm, thickness: $40\;{\mu}m$). Mechanical properties of zeolite-containing LDPE films generally decreased with increasing zeolite content. However, cationic surfactant-modified zeolite film showed the better mechanical properties compared to cation-modified zeolite film. As for the freshness maintenance, the zeolite-containing films modified with cationic surfactants or cations ($Al^{3+},\;Ag^{3+}$) showed the best performance.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.423-429
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• 2008

Currently, Ash-free clean coal producing process by solvent extraction is under development. The produced ash-free clean coal can be directly combusted in a gas turbine which results in substantial improvement of power generation efficiency. However, the clean coal produced by the solvent extraction still contain trace amount of alkali metal which may cause corrosion on turbine blades during the direct combustion. In present work ${\alpha},{\beta}$-metal (Zr and Ti) phosphates and H-Y zeolite were synthesized and their ion exchange characterizations were investigated for the application on alkali metal removal for clean coal production. $Na^+$ ion removal capacities of the metal phosphates and H-Y zeolite were measured and compared in both aqueous solution (100 ppmw, $Na^+$) and coal dissolved N-methyl-2-pyrrolidone (NMP, 12 ppmw $Na^+$) at elevated temperature. In aqueous solution, the ${\beta}$ form metal phosphates showed very high ion exchange capacities compared to ${\alpha}$ form. ${\beta}$ form metal phosphates also showed higher $Na^+$ removal capacities than H-Y zeolite. In ion exchange medium of NMP, all the ${\alpha}$ form metal phosphates showed over 90% of $Na^+$ ion removal efficiency in the temperature range of 200 to 400 while that of H-Y zeolite decreased as a half when the temperature was over 350. In addition, the regenerated metal phosphates by acid treatment showed no sign of degradation in $Na^+$ removal efficiency. Among the metal phosphates used, $Zr_{0.75}Ti_{0.25}(HPO_4)_2$ showed the best performance in $Na^+$ removal and is expected to be the most suitable inorganic ion exchanger for the alkali metal removal process.