• YAKHAK HOEJI
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• v.34 no.5
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• pp.302-310
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• 1990

A study has been made of the Korean bentonite aqueous suspension contrast with American bentonite by means of XRD IR swelling, gel formation and rheogram at various conditions such as concentration, temperature and pH. The Korean bentonite was identified as montmorillonite clay containig a small proprotion of crystoballite and mordenite, and its swelling power were acceptable for requirements of Korean pharmacopeia regulations though its values were not satisfied. Korean bentonite swelled to 10 times and American one did to 15 times compared to its bulkiness of powder. The rheogram of Korean bentonite suspension reveals bulged pseudoplatic flow with yield value at higher concentration and pseudoplastic flow without yield value at lower concentration. The higher the concentration, the greater were the apparent viscosity and hysteresis loop. Korean bentonite suspension showed insignificant temperature dependence on both apparent viscosity and hysteresis loop and it was more temperature dependent on viscosity but less on hysteresis loop than those of American sample. The pH dependence was so high on viscosity that apparent minimum value was near pH 7 and maximum value at pH 3 or 7. The hysteresis loop appeared minimum over the pH range 5-7 and maximum near pH 3 or 11. The Korean bentonite was inferior to the American bentonite in swelling volume, gel formation, thioxotropy, however, it would be possible to improve the quality of Korean bentonite by developing the method of purification for bentonite clay.

• Korean Journal of Environmental Agriculture
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• v.10 no.1
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• pp.11-19
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• 1991

This study was carried out to develop the low-priced adsorbent by synthesizing the zeolite of high CEC with the natural zeolite and examining the ability of this zeolite to adsorb heavy metals. The dominant clay minerals were clinoptilolite and mordenite in natural zeolite, while phillipsite in the synthesized zeolite. Adsorption reaction of Cu and Zn on clays were reached to equilibrium after 1 hr. The amount of adsorption was increased as the concentrations of heavy metals or the initial pH of suspension was increased. The synthesized zeolite adsorbed heavy metals about twice as much as the natural zeolite. The adsorption of heavy metals on the synthesized zeolite was less affected by the initial pH of suspension than that on natural zeolite. At cumulative adsorption, the synthesized zeolite adsorbed much more heavy metals at early three treatments than the natural zeolite did. The amount of desorption by chloride salts was increased as the concentration of chloride salts was increased. The ability of salt to desorb was in the order of NaCl>$CaC1_2$>$AlC1_3$. It is estimated that the ability of the synthesized zeolite to remove heavy metals was better than that of the natural zeolite.

• Korean Journal of Soil Science and Fertilizer
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• v.19 no.3
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• pp.195-203
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• 1986

This study was conducted to investigate the characteristics of surface charge of major clay minerals in Korea. The charge characteristics of clay minerals were studied by measuring the retention of $NH^+_4$, $Ca^{2+}$ and $Cl^-$ as a function of ionic strength. The dominant clay minerals of Zeolite, Bentonite and Kaolin were oriented as Clinoptilolite+Mordenite, Montmorillonite and Halloysite, respectively. At the same ionic strength, Montmorillonite and Halloysite adsorbed some more $Ca^{2+}$ than $NH^+_4$, whereas Zeolite adsorbed more $NH^+_4$ than $Ca^{2+}$. All the three minerals adsorbed more ions with higher ionic strength and the C.F.C was larger in the order of Halloysite < Montmorillonite < Zeolite. Since the total surface area by EGME rentention was shown to be in the order of Halloysite < Zeolite < Montmorillonite, therefore, the charge density was calculated to be in the order of Montmorillonite < Halloysite < Zeolite.

• Archives of Metallurgy and Materials
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• v.64 no.2
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• pp.695-700
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• 2019

Mordenite-zeolite supported Ca-Cu and Ba-Cu catalysts (Ca-Cu/MOR and Ba-Cu MOR) were successfully fabricated for direct decomposition of both NF₃ and N₂O gases contained in waste gas stream of (semiconductor) electronics industry. N₂O conversion rates of Ca-Cu and Ba-Cu catalysts were 79 and 86%, respectively, at 700℃ and 1 atm under space velocity of 5000 h^-1. The Ca-Cu catalyst was especially noteworthy in that its capability of converting N₂O could be maintained even after its exposure to co-feeding NF₃ gas constituent in the waste gas stream. Compositional and surface morphological analyses of the Ca-Cu and Ba-Cu catalysts were made before and after exposure to the waste gas stream to examine any noticeable degradation or change of the catalysts. Unlike Ba-Cu catalyst, SiO₂ constituent of the Ca-Cu catalyst was found to remain immune to the NF₃-cofeeding waste gas stream, casting a positive prospect for superior and steady N₂O decomposition performance via maintenance of its structural integrity.

• Journal of the Mineralogical Society of Korea
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• v.16 no.2
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• pp.135-149
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• 2003

Domestic zeolite ores are mostly composed of Ca-type clinoptilolite, accompanying a little amounts of mordenite. However, other types of zeolite ores rich in ferrierite, heulandite, or mordenite are less commonly found. Based on the quantitative XRD analysis, zeolite contents are determined to be nearly 50∼90 wt%. Impurities (mostly ＞ 10 wt%) in the zeolite ores chiefly consist of quartz, feldspar, smectite, and opal-CT. The determined CEC values ($CEC_{AA}$ ) of powdery samples (grain size: < 125 $\mu\textrm{m}$) of zeolite ores by the Ammonium Acetate method are mostly higher than 100 meq/100 g. Some zeolites from the Guryongpo area, corresponding to the clinoptilolite ore, are measured to be dominantly high in CEC values ranging 170∼190 meq/100 g. Cation exchange property of the zeolite ores varies greatly depending on the types or zeolite species present in the ores. Despite of the lower grade in zeolite content, the $CEC_{AA}$ of ferrierite ore is comparatively high. Compared to this, the $CEC_{AA }$ of heulandite ore is very low, though the zeolite ore exhibits the highest grade ranging up to about 90 wt%. In addition, the CEC values calculated theoretically from the framework composition of clinoptilolite-heulandite series are not consistent with those determined by the cation exchage experiment. The measured $CEC_{AA}$ of clinoptilolite ores are generally higher than those of heulandite ores. This may be due to the higher Ca abundance in exchangeable cation composition and the presence of probable stacking faults in heulandite. The variation of $CEC_{CEC}$ is roughly proportional, though not strictly compatible, to the zeolite contents in clinoptilolite ores. It seems to be caused by the fact that the $CEC_{AA}$ of clinoptilolite locally varies depending on crystal-chemical diversity, i. e., the variation in framework composition (Si/Al) and exchangeable cation composition (especially, the contents of Ca and K). In addition, the determined CEC values ($CEC_{MB}$ ) of zeolite ores by the Methylene Blue method are much higher than those calculated from smectite contents. It suggests a probable reaction of Methylene Blue ion ($C_{16}$ $H_{18}$ $N_3$S+) with larger-pore zeolites than clinoptlolite-heulandite series, i.e., ferrierite and mordenite as well as with smectite. This can be supported by the fact that the ferrierite ore accompanying little amount of smectite has the highest value in CE $C_{MB}$ .

• Economic and Environmental Geology
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• v.55 no.1
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• pp.63-76
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• 2022

Dacitic tuffs, 97 to 118 m thick, were recovered from the lower part of the subsurface Seongdongri Formation, Janggi Basin, which was drilled to assess the potential for underground storage of carbon dioxide. The tuffs are divided into four depositional units(Unit 1 to 4) based on internal structures and particle componentry. Unit 1 and Units 3/4 are ignimbrites that accumulated in subaerial and subaqueous settings, respectively, whereas Unit 2 is braided-stream deposits that accumulated during a volcanic quiescence, and no dacitic tuff is observed. A series of analysis shows that mordenite and clinoptilolite mainly fill the vesicles of glass shards, suggesting their formation by replacement and dissolution of volcanic glass and precipitation from interstitial water during burial and diagenesis. Glass-replaced clinoptilolite has higher Si/Al ratios and Na contents than the vesicle-filling clinoptilolite in Units 3. However, the composition of clinoptilolite becomes identical in Unit 4, irrespective of the occurrence and location. This suggests that the Si/Al ratio and pH in the interstitial water increased with time because of the replacement and leaching of volcanic glass, and that the composition of interstitial water was different between the eastern and western parts of the basin during the formation of the clinoptilolite in Units 1 and 3. It is also inferred that the formation of the two zeolite minerals was sequential according to the depositional units, i.e., the clinoptilolite formed after the growth of mordenite. To summarize, during a volcanic quiescence after the deposition of Unit 1, pH was higher in the western part of the basin because of eastward tilting of the basin floor, and the zeolite ceased to grow because of the closure of the pore space as a result of the growth of smectite. On the other hand, clinoptilolite could grow in the eastern part of the basin in an open system affected by groundwater, where braided stream was developed. Afterwards, Units 3 and 4 were submerged under water because of the basin subsidence, and the alkali content of the interstitial water increased gradually, eventually becoming identical in the eastern and western parts of the basin. This study thus shows that volcanic deposits of similar composition can have variable distribution of zeolite mineral depending on the drainage and depositional environment of basins.

• Membrane Journal
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• v.29 no.5
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• pp.263-275
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• 2019

In the present study, thickness of MOR zeolite membranes was controlled by changing seed size, seeding amount, and aging time of hydrothermal solution, and then effect of membrane thickness on pervaporative ethanol dehydration for 90 wt.% ethanol-water mixture was investigated. First, nanosize MOR zeolite seeds with a diameter of 20 to 30 nm was successfully prepared by planetary milling a laboratory synthesized MOR zeolites and the coating amount was controlled by seed concentration and infiltration volume of coating solution during vacuum-assisted seeding. As seeding amount decreased, membrane thickness was reduced up to around $4{\mu}m$. The MOR zeolite membrane having a thickness of $4{\mu}m$ showed a water/ethanol separation factor of 760 and water flux of $1.0kg/m^2h$. The excellent water flux was due to the reduced membrane thickness which was derived from the nanosize seed. Therefore, it could be concluded that membrane thickness control by using nanosize seed can be a crucial factor to improve pervaporative water flux of MOR zeolite membrane.

• Journal of the Korean Chemical Society
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• v.37 no.3
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• pp.317-326
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• 1993

The acid catalytic reactions of toluene with n-propylalcohol were investigated and the adsorption experiments of dialkylbenzene isomers were carried out at 100$^{\circ}C$ over modified HZSM-5 zeolites. ZSM-5 zeolite was synthesized by the hydrothermal reaction using 4-propylammonium ion, sodium aluminate and colloidal silica etc., and several zeolite catalysts, including H-, K-, Sr-, P-Mg-HZSM-5, H-Y and H-mordenite, were prepared by conventional methods. The main reaction products of toluene with n-propylalcohol over HZSM-5 catalyst include not only xylenes, propyltoluenes, but also ethyltoluenes and high para-selectivity among dialkylbenzene isomers was observed on P-Mg-HZSM-5 zeolite. The diffusion coefficients of various p-dialkylbenzenes are nearly the same, about 1 ${times}$ 10$^{-10}$ cm$^2$/sec and that of m-xylene was about one tenth of o-xylene. These reaction and adsorption characteristics were interpreted in the light of the shape-selectivity related to related to the zeolite pore structure and the zeolitic acidity.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.345-353
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• 2022

This study aimed to fundamentally understand changes of cell parameters of cation-exchanged mordenites using high resolution X-ray powder diffraction for studies that immobilization of various heavy metal cation using synthesis mordenite (Na_6.6Al_6.6Si_41.4O₉₆·20.4H₂O, Na-MOR). As a results of measurement by Thermogravimetric analysis (TGA), it was confirmed that 19.4, 20.4 water molecules per unit cell were present in monovalent-cation substituted MOR (Cs-MOR, Na-MOR), and 21, 23.1, 23.2 water molecules per unit cell were present in divalent-cation substituted MOR (Pb-MOR, Sr-MOR, Cd-MOR). The space group of all the samples were identified as Cmcm belonging to the orthorhombic crystal system. Compared to Na-MOR, starting material, relative peak intensity of (110) and (200) is significantly changed after cation substitution whereas peak position is almost similar. Also, (220) peak that was not found in Na-MOR was clearly observed in Pb-, Cd- and Sr-exchanged MOR. Thus, it was estimated that changes of atomic distribution usually occurred on ab-plane while changes of cell parameters were little. Detailed changes in the cell parameters of cation-exchanged mordenites were derived from whole profile fitting method using the GSAS suite program. Changes in the axial lengths and unit cell volume of cation substitution showed different relationship depending on ionic radius and charge number. In case of monovalent-cation substituted MOR, the length of a-axis increases whereas the length of b- and c-axis decrease by absorbed cation radius. In the case of divalent-cation exchanged MOR, the length of a-axis usually decreases while the length of b- and c-axis increases by cation radius. It was confirmed that unit cell volume of monovalent and divalent cation substituted MORs had an independent tendency by cation radius.

• Applied Biological Chemistry
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• v.25 no.2
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• pp.99-104
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• 1982

Natural zeolite rock was pulverized and dispersed in water. Clay fraction was collected by sedimentation method. The dominant clay mineral was Clinoptiolite with some Mordenite and Smectite. $P^{32}$ adsorption on Na-zeolite was determined in different ionic strengths using $P^{32}$ isotope by sludge method. The lower the pH of suspension, the longer the contact time, and the more the amount of zeolite, the more inorganic P was adsorbed by Na-zeolite, whereas the more P adsorption per unit gram of zeolite was observed at a 100mg addition than a 200mg in same volume of P-NaCl solution (20ml), indicating that the whole positively charged surface of Na-zeolite was not occupied by inorganic P. Furthermore, the more P adsorption on Na-zeolite was observed in higher ionic strength than in the lower. The maximum P adsorption on Na-zeolite was about 1me/g, and the zero point charge (ZPC) is assumed to be below pH 3.7.