• Journal of the Mineralogical Society of Korea
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• v.16 no.3
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• pp.201-213
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• 2003

The adsorption property and ability of domestic zeolites for some heavy metal ions (Ag, Pb, Cr, Cu, Zn, Mn), which may cause a serious environmental problem in industrial wastewater, were evaluated on ore unit through a series of adsorption experiments together with careful examinations of mineral composition and properties of the zeolites. Though the adsorption behavior basically took place in the form of a cation exchange reaction, the higher CEC value does not necessarily to imply the higher adsorption capacity for a specific heavy metal. A general trend of the adsorption selectivity for heavy metals in the zeolites is determined to be as follow: $Ag\geq$Pb>Cr,Cu$\geq$Zn>Mn, but the adsorption properties of heavy metal ions somewhat depend on the species and composition of zeolite. Clinoptilolite tends to adsorb selectively Cu in case of Cr and Cu, whereas heulandite prefers Cr to Cu. A dominant adsorption selectivity of the zeolite ores for Ag and Pb is generally conspicuous regardless of their zeolite species and composition. The zeolite ores exhibit a preferential adsorption especially for $Ag^{+}$ so as not to regenerate when treated with $Na^{+}$ . In the adsorption capacity for heavy meta ions, the zeolites differ in great depending on their species: ferrierite>clinoptilolite>heulandite. Considering the CEC value of mordenite, the mordenite-rich ore appears to be similar to the clinoptilolite ore in the adsorption capacity. The adsorption capacity for heavy metals is not positively proportional to the CEC values of the zeolites measured by the exchange reaction with ammonium ion. In addition, the adsorption capacity roughly tends to depend on the zeolite contents, i.e., the grade of zeolite ore, but the trend is not consistent at all in some ores. These may be caused by the adsorption selectivity for some specific heavy metals, the presence of possible stacking micro-faults and natural cations such as K hardly to exchange in the zeolite. Considering the economic availability and functional effectiveness as natural zeolite resources, clinoptilolite ores could be applicable to utilize the domestic zeolites for the removal of heavy metals.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3696-3701
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• 2011

The single-crystal structure of partially dehydrated partially $Mg^{2+}$-exchanged zeolite Y, ${\mid}Mg{30.5}Na_{14}(H_2O)_{2.5}{\mid}$ [$Si_{117}Al_{75}O_{384}$]-FAU per unit cell, ${\alpha}$ = 25.5060(1) ${\AA}$, dehydrated at 723 K and $1{\times}10^{-4}$ Pa, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd$\bar{3}$ m at 100(1) K. The structure was refined using all intensities to the final error indices (using only the 561 reflections with $F_{\circ}$ > $4{\sigma}(F_{\circ})$) $R_1$ = 0.0377 (Based on F) and $R_2$ = 0.1032 (Based on $F^2$). About 30.5 $Mg^{2+}$ ions per unit cell are found at four different crystallographic sites. The 14 $Mg^{2+}$ ions occupy at site I at the center of double 6-ring (Mg-O = 2.231(3) ${\AA}$, O-Mg-O = $89.15(11)^{\circ}$ and $90.85(11)^{\circ}$). Four $Mg^{2+}$ ions are found at site I' in the sodalite cavity; the $Mg^{2+}$ ions are recessed 1.22 ${\AA}$ into the sodalite cavity from their 3-oxygen plane (Mg-O = 2.20(3) ${\AA}$ and O-Mg-O = $92.3(14)^{\circ}$). Site II' positions (opposite single 6-rings in the sodalite cage) are occupied by 2.5 $Mg^{2+}$ ions, each coordinated to an $H_2O$ molecule (Mg-O = 2.187(20) ${\AA}$ and O-Mg-O = $114.2(16)^{\circ}$). The 10 $Mg^{2+}$ ions are nearly three-quarters filled at site II in the supercage, being recessed 0.12 ${\AA}$ into the supercage (Mg-O = 2.123(4) A and O-Mg-O = $119.70(19)^{\circ}$). About 14 $Na^+$ ions per unit cell are found at one crystallographic site; the $Na^+$ ions are located at site II in the supercage (Na-O = 2.234(7) ${\AA}$ and O-Mg-O = $110.5(4)^{\circ}$).

• Journal of radiological science and technology
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• v.29 no.3
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• pp.147-155
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• 2006

The crystal structures of fully dehydrated $K_3Na_8H-A(R_1=0.0478,\;R_2=0.0458\;and\;a=12.257(1){\AA})$ have been studied by single-crystal x-ray diffraction methods in the cubic space group. Pm3m in order to understand the structure of the zeolite as a gas storage medium and the mechanisms based on the encapsulation and decapsulation processes of gas molecules. In the crystal structures of dehydrated $K_3Na_8H-A$, three $K^+$ ions per unit cell are located on the 8-oxygen ring(0.0, 0.4531, 0.4531) and eight $Na^+$ ions per unit cell are located near the centers of 6-oxygen rings. Each $K^+$ ions on the 8-ring is $2.87(2){\AA}$ and $2.79(1){\AA}$ away from two kinds of framework oxygen atoms. These values are more realistic than previously known values in $K_{12}Na-A$. The exact positions of $K^+$ ions are ca. $0.8{\AA}$ away from the centers of the 8-rings which are previously reported as the preferred location of $K^+$ ions. Because the zeolites frameworks are stabilized as the results, more effective controls of gas molecules at encapsulation, decapsulation, and storage are achieved. Additionally, the available storage volumes are also maximized and more volume of gases can be stored in the materials. Therefore, oxygen storage bottles in hospital can be minimized and portable oxygen bottles for patients in emergency can be developed by using the materials.

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.174-179
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• 2021

Recently, hybrid coal research is underway to upgrade low-grade coal. The hybrid coal is made by mixing low-grade coal with bioliquids such as molasses, sugar cane, and lignin. In the case of lignin used here, a large amount of lignin is included in the wastewater of the papermaking process, and thus, research on hybrid coal production using the same is attracting attention. However, since a large amount of metal ions are contained in the lignin wastewater from the papermaking process, substances that corrode the generator are generated during combustion, and the amount of fly ash is increased. To solve this problem, it is essential to remove metal ions in the lignin wastewater. In this study, metal ions were removed by ion exchange with a alumina hollow fiber membrane coated with K-Phillipsite (K-PHI) zeolite. The alumina hollow fiber membrane used as the support was prepared by the nonsolvent induced phase separation (NIPS) method, and K-PHI seeds were prepared by hydrothermal synthesis. The prepared K-PHI seed was seeded on the surface of the support and coated by secondary growth hydrothermal synthesis. The characteristic of prepared coating membrane was analyzed by Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDX), and the concentration of metal ions before and after ion exchange was measured by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The extraction amount of K+ is 86 mg/kg, and the extraction amount of Na+ is 54.9 mg/kg. Therefore, K-PHI zeolite membrane has the potential to remove potassium and sodium ions from the solution and can be used in acidic lignin wastewater.

• Korean Journal of Crystallography
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• v.15 no.2
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• pp.59-68
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• 2004

Three crystal structures of dehydrated partially $Co^{2+}-exchanged$ zeolite A treated with 0.6 Torr of K at $300^{\circ}C$ (for 12 hrs, 6 hrs, and 2 hrs) vapor have been determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m at 21(1)$^{\circ}C(a=12.181(1)\;{\AA},\;a=12.184(1)\;{\AA},\;and\;a=12.215(1)\;{\AA})\;respectively)$. Their structures were refined to the final error indices, R(weight) of 0.090 with 10 reflections, 0.091 with 82 reflections, and 0.090 with 80 reflections, respectively, for which $1>\sigma(I)$. In each structure, all four $Co^{2+}$ and four $Na^+$ ions to be reduced by K atoms. The cobalt and sodium atoms produced are no longer found in the zeolite. K species are found at five different crystallographic sites: three $K^+$ ions lie at the planes of 8-rings, filling that position, ca. 11.5 K^+$ ions lie on threefold axes, ca. 4.0 in the large cavity and ca. 4.0 in the sodalite cavity, and ca. 0.5 $K^+$ ion is found near a 4-ring. ca. three $K^0$ atoms are found deep into the large cavity on threefold axes. In these structures, crystallographic results show that cationic tetrahedral $K_4$ (and/or triangular $K_3$) clusters have formed in the sodalites of zeolite A. The $K_4$ and/or $K_3$ clusters coordinate trigonally to three oxygens of a six-oxygen ring. The partially reduced ions of these clusters interact primarily with oxygen atoms of the zeolite structure rather than with each other. ca. 14.5K species are found per unit cell, more than the twelve $K^+$ ions needed to balance the anionic charge of zeolite framework, indicating that sorption of $K^0$ has occurred. The three $K^0$ atoms in the large cavity are closely associated with three out of four $K^+$ ions in the large cavity to form $K_7^{4+}$ clusters. The $K_7^{4+}$ cluster not interacts primarily with framework oxygens.

• Journal of the Korean institute of surface engineering
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• v.26 no.6
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• pp.285-290
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• 1993

A series of samples were prepared by treating natural zeolite from Kampo area with HCl and NaOH. And, the adsorption characteristics of some liquid samples were investigated by the Diamond-Kinter method. The adsorption amount of all liquid investigated was more effective in acid treatment than in alkali treatment. In the case of n-, iso-C3H7OH, thed adsorption amount of n-form which has smaller molecular size was larger. Similar tenedncy was observed in n-, iso-C4H9OH, but the amount was lower than n-, iso-C3H7OH. In CHCl3 and CCl4, that of CHCl, which is smaller molecular size and has polarity, was far lager. From the view of the molecular size, adsorption amount of C6H5CH3 and p-C6H4(CH3)2 showed the characteristics of surface activity rather than chemical treatment.

• Bulletin of the Korean Chemical Society
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• v.19 no.4
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• pp.466-470
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• 1998

Catalytic hydrogenation of carbon dioxide for the simultaneous synthesis of methanol and dimethyl ether (together called oxygenates) over a combination of methanol synthesis and methanol dehydration catalysts has been studied. Various methanol synthesis and methanol dehydration catalysts were examined for this reaction. The addition of promotors like $Ga_2O_3\; and\; Cr_2O_3$ to Cu/ZnO catalyst gave much more enhanced yield on the formation of oxygenates. From the results, the promotional effect of $Cr_2O_3$ has been explained in terms of increase in the intrinsic activity of Cu while that of $Ga_2O_3$ being increase in the dispersion of Cu. Among the methanol dehydration catalysts examined, the solid acids bearing high population of intermediate-strength acid sites were found to be very effective for the production of oxygenates. HY zeolite which contains strong acid sites produce small amount of hydrocarbons as by-products. However, CuNaY zeolite in which the presence of strong acid sites are minimum gives very high oxygenates yield without the formation of hydrocarbons.

• Journal of Energy Engineering
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• v.6 no.1
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• pp.26-33
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• 1997

Highly crystalline Cu-ZSM5 was prepared without using organic templates. Several ion exchange treatments between Na$\^$＋/ and Cu$\^$2＋/ brought about excess loading of copper ions on the ZSM5 zeolite and the resultant zeolite was active for the decomposition of NO. This indicates that the copper ions excessively loaded on the ZSM5 zeolite are effective for the NO decomposition. When oxygen was added to a reactants, the conversion of NO decreased. NO, O$_2$TPD experiments explained that the active sites for NO decomposition and the adsorption sites of O$_2$, were the same. O$_2$, at the surface of ZSM5 zeolite was desorbed incompletely after pretreatment at 500$^{\circ}C$, and CU-ZSM5 pretreated with H$_2$at 500$^{\circ}C$ showed promoted activity at the start of reaction. Thus, it seems clear that O$_2$, adsorbed ai the surface of catalyst inhibits the catalytic activity.

• Membrane Journal
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• v.28 no.6
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• pp.432-443
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• 2018

In this study, propylene/propane separation behavior of Na-type faujasite zeolite membranes is predicted by observing gravimetric adsorptions of propylene and propane on zeolite 13X. The gravimetric adsorptions were measured by using a magnetic suspension balance (MSB) at temperatures of 323, 343, 363 K and a pressure range of 0.02-1 bar. The pressure was increased at 0.1 bar intervals. As adsorption temperature increased, adsorptions of propylene and propane decreased and propylene/propane adsorption selectivity increased. Also, the diffusion coefficients of propylene and propane were increased as the adsorption temperature increased, following the Arrhenius equation. The maximum propylene/propane diffusion selectivity was 0.9753 at 323 K. The perm-selectivity was calculated from the adsorption data of zeolite 13X and compared with the perm-selectivity measured in the single gas permeation experiment for the Na-type faujasite zeolite membrane. The maximum values for the calculated and measured perm-selectivities were observed at a temperature of 323 K. It could be concluded that the prediction of propylene/propane separation of surface diffusion-based membrane by using gravimetric adsorption data is reasonable. Therefore, it is expected that this prediction method can be applied to the screening of adsorption-based microporous membrane for propylene/propane separation.

• Membrane Journal
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• v.17 no.3
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• pp.254-268
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• 2007

Sodium type faujasite(FAU) zeolite layers with diverse materials characteristics(Si/Al ratio, thickness, and structural discontinuity) were hydrothermally grown on a porous $\alpha-Al_2O_3$ tube, and then the $CO_2/N_2$ separation was evaluated at $30^{\circ}C$ for an equimolar mixture of $CO_2$ and $N_2$. Among hydrothermal conditions, $SiO_2$ content in hydrothermal solution seriously affected materials characteristics: with an increment in the $SiO_2$ content, Si/Al ratio, thickness, and structural discontinuity of grown FAU zeolite layer simultaneously increased. The present study reveals that structural discontinuity(intercrystalline voids due to an incomplete densification and cracks induced by GIS Na-P1 phase) is the most important variable affecting the $CO_2/N_2$ separation. Also, it was suggested that the $CO_2$ desorption in permeate side be the rate-determining(slowest) step in the overall $CO_2$ permeation.