• Bulletin of the Korean Chemical Society
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• v.6 no.4
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• pp.202-206
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• 1985

The crystal structure of The crystal structure of $Ag^+$-Exchanged Zeolite A, $Ag_{4.6}Na_{7.4}-A$, dehydrated, treated with $H_2$, and evacuated, all at $350^{\circ}C$, has been determined by single crystal x-ray diffraction methods in the cubic space group Pm3m at $24(1)^{\circ}C;$ a = $12.208(2)\AA.$ The structure was refined to the final error indices R1 = 0.088 and R2 (weighted) = 0.069 using 194 independent reflections for which II_0$ > $3{\sigma}(I_0)$. On threefold axes near the centers of 6-oxygen rings, $7.4 Na^+$ ions and $0.6 Ag^+$ ions are found. Two non-equivalent 8-ring $Ag^+$ ions are found off the 8-ring planes, each containing about $0.6 Ag^+$ ions. Three non-equivalent Ag atom positions are found in the large cavity, each containing about 0.6 Ag atoms. This crystallographic analysis may be interpreted to indicate that $0.6 (Ag_6)^{3+}$ clusters are present in each large cavity. This cluster may be viewed as a nearly linear trisilver molecule $(Ag_3)^0$ (bond lengths, 2.92 and 2.94 $\AA;$ angle, $153^{\circ})$ stabilized by the coordination of each atom to a Ag^+$ ion at 3.30, 3.33, and 3.43 $\AA$, respectively. In addition, one of the silver atoms approaches all of the 0(1) oxygens of a 4-ring at $2.76\AA.$ Altogether $7.4 Na^+$ ions, $1.8 Ag^+$ ions, and 1.8 Ag atoms are located per unit cell. The remaining $1.0 Ag^+$ ion has been reduced and has migrated out of the zeolite framework to form silver crystallites on the surface of the zeolite single crystal.

• Membrane Journal
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• v.16 no.1
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• pp.25-30
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• 2006

The NaA zeolite membrane was synthesized on the surface of a porous ${\alpha}$-alumina support from the reaction solution composed of 1Si : 1Na : 4Na $6H_{2}O$. The pervaporation performance of the synthesized NaA zeolite membrane was investigated for the iso-propyl alcohol (IPA) aqueous solution according to the different feed concentration and the different operating temperature. The total flux decreases by increasing the feed IPA concentration and increases by increasing the temperature. The total flux was about $4.0{\times}10^3g/m^2\;hr\;at\;60^{\circ}C$ and 0.6 mole fraction of IPA and the separation factor was $1.8{\times}10^7\;at\;60^{\circ}C$ and 0.8 mole fraction of IPA. The separation performance of water through the NaA membrane was found to be superior to that obtainable with a distillation process just by comparison of the vapor-liquid equilibrium data.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.749-756
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• 2019

Na-X and Na-A zeolites that give high adsorption capacity for heavy metals in an aqueous system were synthesized from the coal fly ash obtained from a thermoelectric power plant using a fusion method. The characteristics and Cu(II) adsorption capacity of the synthetic zeolites were also compared to those of using a commercial zeolite. For the selection of optimum conditions of zeolite synthesis, the effects of major parameters in the fusion method such as a dosage ratio of NaOH, aging time, hydrothermal reaction time, and also the dosage ratio of NaAlO₂ (Na-A) on the characteristics and Cu(II) adsorption capacity of the synthetic zeolites were studied. For the analysis of characteristics of the synthetic zeolites, X-ray diffraction (XRD), cation exchange capacity (CEC), Brunaue-Emmett-Teller (BET) and scanning electron microscopy (SEM) were used. The optimum conditions for the synthesis of zeolites with a high adsorption capacity for cationic heavy metals including Cu(II) were the aging time of 6 h, hydrothermal reaction time of 6 h and NaOH and NaAlO₂ dosage ratio of 1.5 and 0.5 (Na-A), respectively. According to the Langmuir isotherm test, maximum Cu(II) adsorption capacities of the synthetic and commercial Na-X and Na-A zeolites were found to be 90.1, 105.26, 102.05, and 109.89 mg/g, respectively. This indicates that the adsorption capacity of synthetic zeolites was comparable to commercial ones. The results of this study also suggest that the coal fly ash can be potentially used as a raw material for the zeolite synthesis.

• Journal of environmental and Sanitary engineering
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• v.12 no.3
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• pp.61-71
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• 1997

This study was conducted to examine the adsorption capacity of $NH_{3}-N$ by natural zeolite for the purpose of investigating the possibility for $NH_{3}-N$ eliminator of korea natural zeolite. The dominant clay minerals of zeolite was clinoptiloite. The amount of $NH_{3}-N$ adsorption by zeplite was not significantly affected by the particle size of zeolite and increased with increasing the ratio of zeolite to the volume of solution. Removal ratio of 100% of NH$_{3}$-N by non, 1st, 2nd regenerated cloumn was continued separately during 4.5, 18, 30hr and this amount was each 0.081, 0.324, 0.540g $NH_{3}-N/zero$.100g. The eluenting amount of K, Ca, Mg was increased on the zeolite cloumn according to that of Na decreased. The amount of 74% of $NH_{3}-N$ was desorved on the zeolite cloumn for regenerating treatment during 8hr. The perfect removal amount was $0.216gNH_{3}-N/zero$.100g on the zeolite cloumn with field sample.

• Journal of the Korean institute of surface engineering
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• v.21 no.1
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• pp.47-52
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• 1988

The purpose of th this study was to determine an adsorption capaty of cesium by domestic zeolite, clinoptilolite, which has adsorption selectivity and resistence to radiolytic degradation, and to find the operation of column packed natural or Na cinoptiloite. The exchange capacity of cesium was 0, 875 m eq-per gram of clinopilolite. Na clinoptilolite was mire effective for cesium removal than naturl clioptilolite. Then, the results show that the domestic cilnoptilolite activated with sodium hydroxide colud be applicable for removal of cesium from liquid radwastes.

• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1675-1682
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• 2007

Large colorless single crystals of faujasite-type zeolite with diameters up to 200 μm have been synthesized from gels with the composition of 3.58SiO2:2.08NaAlO2:7.59NaOH:455H2O:5.06TEA:1.23TCl. Two of these, colorless octahedron about 200 μm in cross-section have been treated with aqueous 0.1 M TlC2H3O2 and KNO3 in order to prepare Tl+- and K+-exchanged faujasite-type zeolites, respectively, and then determined the Si/Al ratio of the zeolite framework. The crystal structures of |Tl71|[Si121Al71O384]-FAU and |K53Na18|[Si121Al71O384]-FAU per unit cell, a = 24.9463(2) and 24.9211(16) A, respectively, dehydrated at 673 K and 1 × 10-6 Torr, have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd m at 294 K. The two single-crystal structures were refined using all intensities to the final error indices (using only the 905 and 429 reflections for which Fo > 4σ(Fo)) R1/R2 = 0.059/0.153 and 0.066/0.290, respectively. In the structure of fully Tl+-exchanged faujasite-type zeolite, 71 Tl+ ions per unit cell are located at four different crystallographic sites. Twenty-nine Tl+ ions fill site I' in the sodalite cavities on 3-fold axes opposite double 6-rings (Tl-O = 2.631(12) A and O-Tl-O = 93.8(4)o). Another 31 Tl+ ions fill site II opposite single 6-rings in the supercage (Tl-O = 2.782(12) A and O-Tl-O = 87.9(4)o). About 3 Tl+ ions are found at site III in the supercage (Tl-O = 2.91(6) and 3.44(3) A), and the remaining 8 occupy another site III (Tl-O = 2.49(5) and 3.06(3) A). In the structure of partially K+-exchanged faujasite-type zeolite, 53 K+ ions per unit cell are found at five different crystallographic sites and 18 Na+ ions per unit cell are found at two different crystallographic sites. The 4 K+ ions are located at site I, the center of the hexagonal prism (K-O = 2.796(8) A and O-K-O = 89.0(3)o). The 10 K+ ions are found at site I' in the sodalite cavity (K-O = 2.570(19) A and O-KO = 99.4(9)o). Twenty-two K+ ions are found at site II in the supercage (K-O = 2.711(9) A and O-K-O = 94.7(3)o). The 5 K+ ions are found at site III deep in the supercage (K-O = 2.90(5) and 3.36(3) A), and 12 K+ ions are found at another site III' (K-O = 2.55(3) and 2.968(18) A). Twelve Na+ ions also lie at site I' (Na-O = 2.292(10) and O-Na-O = 117.5(5)o). The 6 Na+ ions are found at site II in the supercage (Na-O = 2.390(17) A and O-Na-O = 113.1(11)o). The Si/Al ratio of synthetic faujasite-type zeolite is 1.70 determined by the occupations of cations, 71, in two single-crystal structures.

• Resources Recycling
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• v.11 no.3
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• pp.3-9
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• 2002

Relnoval of ammonia from aqueous solutions has been studied with zeolite and bentonite minerals. Zeolite and bentonite powder were supplied by a domestic company and used as delivered without further purification. The aqueous pH was found to increase by addition of zeolite or bentonite up to pH 8.5 from initial pH of 5.5∼5.7. From the C.E.C. measurement by ammonium acetate leaching method, the values of C.E.C. of zeolite and bentonite sample were observed to be 129.7 meq/100 gr and 65.1 meq/100 gr, respectively and Na+ ion accounted for the major part of total C.E.C. in both cases. In the removal of ammonia with zeolite and bentonite, physical adsorption of ammonium ion onto minerals was believed to contribute to the removal of it as well as the intrinsic cation exchange reaction. Finally, zeolite was found to be superior to bentonite in the removal of ammonia from aqueous solutions.

• Journal of the Korean Chemical Society
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• v.33 no.6
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• pp.623-632
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• 1989

The positions and interaction energies of framework atoms and water molecules of $Mn^{2+}$-exchanged zeolite A were calculated using some potential energy functions and an optimization program. The sum of interaction energies of framework atoms in dehydrated $Mn_{4,5}Na_3-A$ was approximately the same as those of thermally stable $Ca^{2+}$-or $Mg^{2+}$-exchanged zeolite A. Since $Mn^{2+}$ ions can form good coordination bonds with framework oxygens even in dehydrated state, $Mn^{2+}$-exchanged zeolite A is considered to be thermally stable. The optimized positions of framework atoms and ions in this work are agreed well with the crystallographic data. Three groups of water molecules are found in hydrated $Mn^{2+}$-exchanged zeolite A; W(I) group of water molecules having only hydrogen bonds, W(II) group coordinated to $Na^+$ ion, and W(III) group coordinated to $Mn^{2+}$ ion. The average binding energy of each group of water molecules decrease in the order of W(III) > W(II) > W(I). The activation energies in the dehydration reaction of each group of water molecules increased in accordance with their binding energy.

• Journal of Environmental Science International
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• v.20 no.11
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• pp.1437-1445
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• 2011

The adsorption performance of lead ion was studied using five zeolites (Na-P1, sodalite (SOD), analcime (ANA), nepheline hydrate (JBW), cancrinite (CAN)) synthesized from Jeju scoria. The adsorption performances of lead ion decreased in the order of Na-P1 > SOD > ANA > JBW > CAN. These results showed that the synthetic zeolite with a higher cationic exchange capacity showed a higher adsorption performance. The uptake of lead ion by synthetic zeolites were described by Freundlich model better than Langmuir model. The adsorption kinetics of lead ion by synthetic zeolites fitted the pseudo 2nd order kinetics better than pseudo 1st order kinetics. The effective diffusion coefficients of lead ion by synthetic zeolites were ten times higher than the zeolite A synthesized from coal fly ash.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.323-327
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• 2011

A zeolite sheet (ceramic paper containing zeolite) made in a cylindrical configuration can be applied to a honeycomb rotor for the effective VOC removal. In this study, the zeolite sheet containing ZSM-5 was used as a support for Pt-loading, and its catalytic activity for the toluene combustion reaction was compared with those of the other Pt catalysts loaded on ${\gamma}-Al_2O_3$ and cordierite honeycomb. Pt/zeolite sheet catalyst showed a higher activity for toluene combustion reaction than that of $Pt/{\gamma}-Al_2O_3$ or Pt/cordierite honeycomb. On the other hand, the dispersion of Pt particles loaded on the zeolite sheet was improved by the pretreatment with $NH_3-H_2O$ vapor at room temperature. Consequently, the pretreatment of Pt/zeolite sheet by $NH_3-H_2O$ vapor significantly enhanced the catalytic activation for toluene combustion reaction.