• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.38-43
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• 1998

It was realized that the nucleation rate in the synthesis of M-ZSM-5 using various alkali cations such as $Li^+$, $Na^+$, $K^+$ and $Cs^+$ at low temperature and atmospheric pressure was decreased in the order of $Na^+>K^+>Li^+>Cs^+$. Unlike conventional synthesis method at high temperature and pressure, the results showed that at low temperature and atmospheric pressure, the higher the nucleation rate is, the larger the crystal size of M-ZSM-5 obtained ; that is, the crystal size in the order of $K^+>Na^+>Cs^+>Li^+$. In addition, it also suggests that regardless of alkali cations to be used, the current synthesis method can produce M-ZSM-5 with BET surface area greater than $300m^2/g$ within 52hrs. of reaction time, in particular greater than $400m^2/g$ within 32hrs, for $Na^+$ cation.

• Analytical Science and Technology
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• v.10 no.1
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• pp.60-65
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• 1997

Solvent extraction of alkali metal and alkaline earth metal cations by mono-crown ether(benzo-15-crown-5) and bis-(crown ether)s(ethylenediamine bis(4'-formyl benzo-15-crown-5)) containing benzo-15-crown-5 moieties were investigated with water-chloroform system at $25^{\circ}C$. The order of the extraction equilibrium constants($K_e$) and the complexation constants($K_c$) for the alkali metal and alkaline earth metal cations with mono-crown ether and bis-(crown ether)s were Ca(II)>Na(I)>Sr(II)>K(I)>Mg(II)>Rb(I) and Sr(II)>Ca(II)>K(I)>Rb(I)>Mg(II)>Na(I) respectively. These results were explained in terms of the size effect of metal cation and electron density effect. Also, the bis-(crown ether)s was found to extract metal cations more effectively than the corresponding mono-crown ether.

• Journal of Photoscience
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• v.10 no.1
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• pp.127-148
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• 2003

Zeolite is a porous highly interactive matrix. Zeolitic cations help to generate triplets from molecules that possess poor intersystem crossing efficiency. Certain zeolites act as electron acceptors and thus can spontaneously generate radical cations. Zeolites also act as proton donors and thus yield carbocations without any additional reagents. These reactive species, radical cations and carbocations, have long lifetime within a zeolite and thus lend themselves to be handled as ‘regular’ chemicals. Internal structure of zeolites is studded with cations, the counter-ions of the anionic framework. The internal constrained structure and the cations serve as handles for chemists to control the behavior of guest molecules included within zeolites.

• Journal of the Korean Chemical Society
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• v.5 no.1
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• pp.56-59
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• 1961

Ion exchange procedure was studied for the separation of thorium from the acidic solution obtained by means of decomposition of monazite with alkali solution. Present cation exchange method consists of adsorption of cations from the sample solution (ca. 0.6N HCl acidic) onto Amberlite IR-120 resin, elution of all of the rare earth cations with 700 ml. of 2N Hydrochloric acid, and recovery of the thorium by elution with 200ml. of 6N sulfaric acid. Thorium recovery by the ion-exchange method mentioned above, was quantitative, and it is concluded that this ion-exchange method may be used not only for industrial separation of thorium from rare earths but also for quantitative determination of thorium with relative error, ${\pm}1.0.$.

• Bulletin of the Korean Chemical Society
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• v.22 no.6
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• pp.559-564
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• 2001

A method for calculating the main characteristics of a potentiometric titration curve in a carboxylic ion exchanger has been investigated. The potentiometric titration curves of simple electrolyte and ion exchangers (polyelectrolytes) showed a great difference between them. The acidity parameters of the ion exchangers, the thermodynamic constant (pK0), apparent equilibrium constant (K), and correction for the apparent equilibrium constant (b), were introduced and used to express the characteristics of the carboxylic ion exchanger. A characteristic equation related to the acidity parameters of the ion exchangers systems was derived. A fibrous carboxylic cation exchanger was used and potentiometric titration curves at different concentrations of the supporting electrolyte were obtained . To prove the validity of the characteristic equation, the concentration of the supporting electroyte was varied. In the present study, good agreement between the data points and the fitted curves was found in all the cases. The g (number of moles of alkali to 1 g of ion exchanger) of carboxylic ion exchanger was calculated from the concentration of supporting electrolyte (C), pH of the solution, and degree of neutralization of ion exchanger (x).

• Journal of the Mineralogical Society of Korea
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• v.15 no.4
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• pp.329-344
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• 2002

Mineralogical and chemical characterization of some domestic bentonites, such as quantitative XRD analysis, chemical leaching experiments, pH and CEC determinations, were done without any separation procedures to understand their relationships among mineral composition, characteristics, and cation exchange properties. XRD quantification results based on Rietveld method reveal that the bentonites contain totally more than 25 wt% of impurities, such as zeolites, opal-CT, and feldspars, in addition to montmorillonite ranging 30～75 wt%. Cation exchange properties of the zeolitic bentonites are deeply affected by the content of zeolites identified as clinoptilolite-heulandite series. Clinoptilolite is common in the silicic bentonites with lighter color. and occurs closely in association with opal-CT. Ca is mostly the dominant exchangeable cation, but some zeolitic bentonites have K as a major exchangeable cation, The values of cation exchange capacity (CEC) determined by Methylene Blue method are comparatively low and have roughly a linear relationship with the montmorillonite content of the bentonite, though the correlated data tend to be rather dispersed. Compared to this, the CEC determined by Ammonium Acetate method, i.e.‘Total CEC’, has much higher values (50～115 meq/100 g). The differences between those CEC values are much greater in zeolitic bentonites, which obviously indicates the CEC increase affected by zeolite. Other impurities such as opal-CT and feldspars seem to affect insignificantly on the CEC of bentonites. When dispersed in distilled water, the pH of bentonites roughly tends to increase up to 9.3 with increasing the alkali abundance, especially Na, in exchangeable cation composition. However, some bentonites exhibit lower pH (5～6) so as to regard as ‘acid clay’. This may be due to the presence of $H^{＋}$ in part as an exchangeable cation in the layer site of montmorillonite. All the works of this study ultimately suggest that an assesment of domestic bentonites in grade and quality should be accomplished through the quantitative XRD analysis and the ‘Total CEC’measurement.

• Journal of the Korean Chemical Society
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• v.48 no.2
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• pp.129-136
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• 2004

Titanium and [titanium+Na(K)] substituted 11${\AA}$ tobermorites solids synthesized under hydrothermal conditions at 180$^{\circ}C$ exhibit cation exchange properties toward heavy transition metal cations, such as Fe$^{2+},\;Zn^{2+},\;Cd^{2+}\;and/or\;Pb^{2+}$. The amount of heavy metal cations taken up by these solids was found in the order: Fe$^{2+}>Zn^{2+}>Cd^{2+}>Pb^{2+}$, and reached maximum at 10% [Ti+K]-substituted tobermorite. The total cation exchange capacity of the 10% Ti+Na (K) - substituted tobermorites synthesized here range from 71 to 89 meq/100 g, and 50-56 meq/100g for Ti-substituted only. Results indicated that 10% [Ti+K] substitution exhibit cation exchange capacity more 2.4 times than the unsubstituted-tobermorite. This is due to the increase of the number of active sites on the exchangers. The incorporation of Ti and/or [Ti+Na(K)] in the lattice structure of synthesized tobermorites is due to exchange of Ti$^{4+}{\Leftrightarrow}2Ca^{2+}\;and/or\;Ti^{4+}+2Na^+(K^+){\Leftrightarrow}3Ca^{2+}$, respectively. The mechanism of Ti and [Ti+Na(K)] incorporations in the crystal lattice of the solids during synthesis and the heavy metal cations uptaken by these solids is studied.

• Journal of the Korean Chemical Society
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• v.32 no.5
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• pp.443-451
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• 1988

New crown ether dye-Ⅰ and dye-Ⅱ having an azo group(-N=N-) were synthesized from monobenzo-15-crown-5 and dibenzo-18-crown-6. These dyes showed ${\lambda}_{max}$ of 377 and 383nm respectively. The complexes of alkali metal ions ($Na^+$, $K^+$, $Cs^+$) with dye ligands showed band shift (390~400nm) and intensity increased. For a given anion, the extraction constants are in the order of $K^+$ < $Cs^+$ < $Na^+$ for dye-Ⅰ and $Cs^+$ < $Na^+$ < $K^+$ for dye-Ⅱ. These results show that the selectivity of crown ethers toward the alkali metal ions is dependant on the charge density of cation and the size of crown ether cavity. For a given cation, the order of the extraction constant is $Cl^-$ < $Br^-$ < $I^-$ < picrate. This order coincides with the degree of anion solvation effect.

• Korean Journal of Materials Research
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• v.8 no.4
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• pp.368-374
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• 1998

The corrosion characteristics of zirconium alloys have been investigated in various aqueous solutions of LiOH. NaOH, KOH, RbOH. and CsOH at 3S$0^{\circ}C$. The concentrations of solutions were set to 4.3 mmol and 32.Smmol with equimolar $M^+$ and OH . The oxide characterization was performed using TEM on the samples corroded in 32. Smmol LiOH, NaOH, and KOH solution. The samples were prepared to have the same oxide thickness for the pretransition and post- transition regimes. Considering the trend of experimental data, the cation would playa major role in the corrosion process of Zr alloys in alkali hydroxide solutions. The microstructures of the oxides formed in various solutions were quite different. In LiOH solution the oxides grown in pre-transition as well as post-transition had the equiaxed structures with many pores and open grain boundaries. The oxides grown in NaOH solution had the protective columnar structures in pre-transition and the equiaxed structures with many open grain boundaries in post- transition. On the other hand. in KOH solution the columnar structure was maintained from pre- transition to post- transition. It was considered that the cation incorporation into zirconium oxide controlled the oxide characteristics and the corrosion acceleration in alkali hydroxide solutions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.1-8
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• 2012

Since the cement industry is expected to face serious setbacks in the near future associated with environmental concerns. With the advent of new technologies and increased public awareness about global environmental issues, the cement industry is actively seeking to adopt new technologies as part of an effort to diversity its resources. This study is designed to assess the fundamental properties of zeolite cement concrete which consists mainly of natural zeolite, which is known for removal of and harmful gas, ion exchange capacity removing cation contaminant including heavy metals and ammonia, absorptive capacity and molecular sieving effect together with excellent insulation capacity as a porous material, and recently draws much attention for its possibility as an alternative material to cement. The study was conducted to show the compressive strength of concrete, slump, bleeding and air volume according to the changes of natural zeolite and alkali activator(NaOH). As a result of measuring the compressive strength of natural zeolite concrete, it was almost 40MPa and displayed similar to general concrete in the tests of slump, bleeding and air volume, with which it was considered that it may be used as a future high performance, high performance construction material.