• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.3
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• pp.235-243
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• 2006

In this study, an experimental study on the sorption properties of uranium(VI) onto a bentonite colloid generated from Gyeongju bentonite which is a potential buffer material in a high-level radioactive waste repository was performed as a function of the pH and the ionic strength. The bentonite colloid prepared by separating a colloidal fraction was mainly composed of montmorillonite. The concentration and the size fraction of the prepared bentonite colloid measured using a gravitational filtration method was about 5100 ppm and 200-450 nm in diameter, respectively. The amount of uranium removed by the sorption reaction bottle walls, by precipitation, and by ultrafiltration was analyzed by carrying out some blank tests. The removed amount of uranium was found not to be significant except the case of ultrafiltration at 0.001 M $NaClO_4$. The ultrafiltration was significant in the lower ionic strength of 0.001 M $NaClO_4$ due to the cationic sorption onto the ultrafilter by a surface charge reversion. The distribution coefficient $K_d$ (or pseudo-colloid formation constant) of uranium(VI) for the bentonite colloid was about $10^4{\sim}10^7mL/g$ depending upon pH and ionic strength of $NaClO_4$ and the $K_d$ was highest in the neutral pH around 6.5. It is noted that the sorption of uranium(VI) onto the bentonite colloid is closely related with aqueous species of uranium depending upon geochemical parameters such as pH, ionic strength, and carbonate concentration. As a consequence, the bentonite colloids generated from a bentonite buffer can mobilize the uranium(VI) as a colloidal form through geological media due to their high sorption capacity.

• Journal of Life Science
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• v.20 no.12
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• pp.1906-1909
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• 2010

Acid and halide ion catalyses for the hydrolysis of benzenesulfinamides were kinetically investigated. The rates of hydrolysis increased with increasing concentration of both acid and halide ions and also showed to speed up as the electron donating ability of the benzenesulfinyl moiety and the electron withdrawing ability in the leaving group increased. The reactivity of halide ions was in the order of $Br^-$ > $Cl^-$. The reaction mechanism may be accommodated by including a hypervalent intermediate and sulfonium cation.

• Analytical Science and Technology
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• v.14 no.2
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• pp.123-130
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• 2001

Determination of cadmium(II) ion with a perfluorinated sulfonated polymer-ethylenediamine(nafion-en) modified glassy carbon electrode was studied. It was based on the chemical reactivity of an immobilized layer(nafion-en) to yield complex $[Cd(en)_2]^{2+}$. The reduction peak potential by differential pulse voltammetry(DPV) was observed at $-0.780({\pm}0.005)V$ vs. As/AgCl. The linear calibration curve was obtained in cadmium(II) ion concentration range $5.0{\times}10^{-7}-2.0{\times}10^{-5}M$, and the detection limit(3s) was $2.20{\times}10^{-7}M$. The detection limit of nafion-en modified glassy carbon electrode has been shown about 14 higher sensitivity than a bare glassy carbon electrode.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.427-434
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• 2012

Waterborne polyurethane dispersions (PUD) were synthesized from poly (carbonate diol), isophrone diisocyanate and dimethylol propionic acid at different NCO/OH molar ratios. Subsequently, the PUD was mixed with different types of alkali metal salts ($LiClO_4$, $NaClO_4$, and $KClO_4$) to prepare antistatic waterborne polyurethane coating solutions. Effects of the types and amounts of alkali metal salts were investigated on the surface resistances of the resulting coating films. The surface resistances of coating films were decreased with increasing the amounts of alkali metal salts added in the PUD. The coating films prepared with the same amount of alkali metal salts showed increased ionic conductivity with the order of $LiClO_4$ > $NaClO_4$ > $KClO_4$. Also, the surface resistances of coating films were increased with increasing the molar ratios of NCO/OH in the PUD.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.726-730
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• 2019

The removal of calcium ions using zeolite to solve problems of the CaCO₃ manufacturing process using cement kiln dust was investigated. To do so, a modified zeolite was employed and experiments were conducted to select the optimal zeolite type considered the binding cation and structure, evaluate the removal performance of calcium ions, the influence of the type and concentration of the modifying solution, and the removal selectivity when K coexists. Among five zeolites, 13X zeolite was found to have the best calcium ion removal performance, and it was confirmed that the removal performance was enhanced when KCl was used as a modifying solution instead of NaCl. This study is expected to be the basis for the solution of carbonation process and high concentration of KCl recovery technology.

• Analytical Science and Technology
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• v.23 no.6
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• pp.560-565
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• 2010

Perchlorate ion ($ClO_4^-$) has been widely used as oxidizing agent in military weapon system such as rocket and missile fuel propellant. So it has been challenging to remove the pollutant of perchlorate ion. nanoscale zero valence iron (nZVI) particles are widely employing reduction catalyst for decomposition of perchlorate ion. nZVI particles has increasingly been utilized in groundwater purification and waste water treatment. But it have strong tendency of aggregation, rapid sedimentation and limited mobility. In this study, we focused on reduction of perchlorate ion using nZVI particles immobilized in alginate polymer bead for stabilization. The stabilized nZVI particles displayed much greater surface area, and much faster reaction rates of reduction of perchlorate ion. In this study, an efficient way to immobilize nZVI particles in a support material, alginate bead, was developed by using $Ca^{2+}$ as the cross-linking cations. The efficiency and reusability of the immobilized Fe-alginate beads on the reduction of perchlorate was tested at various temperature conditions.

• Journal of Bio-Environment Control
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• v.11 no.3
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• pp.121-126
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• 2002

This study was conducted to investigate the effect of high concentration of sodium salts and chlorides in soil on the growth of tomato and the uptake of minerals. The growth inhibition rates of plant height and dry weight were different depending on salts, but they were not related to the electric conductivities (EC) and acidities (pH) in the soil solution. The orders of growth inhibition were Cl, SO$_4$, CO$_3$, PO$_4$＞NO$_3$ in the sodium salts series, and Na, K, Mg, NH$_4$＞Ca in the chlorides. The growth inhibition rates of the sodium salts series tended to be larger than those of the chloride series. Yield was lower 30%~10% in the sodium salt and chloride series than in the control. Chlorophyll content, photosynthetic rate and stomatal conductance were lower in the sodium salts and chloride series than in the control. Mineral concentration was lower in sodium salts and chlorides than in control. The nitrate absorption was inhibited in all salts except for NaNO$_3$ and NH$_4$Cl, and specially in NaCl and Na$_2$SO$_4$ treatments of the sodium salts and in KCl treatment of chloride series. K concentration was reduced NaCl and Na$_2$SO$_4$ treatments compared with the other salts. In the sodium salt series, calcium and magnesium concentration were decreased antagonistically when sodium concentration was increased.

• Analytical Science and Technology
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• v.5 no.1
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• pp.33-39
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• 1992

THF-based crown-4 of 16-membered rings having tetrahydrofuran unit was synthesized by an acid-catalyzed condensation of furan and acetone followed by hydrogenation in an effort to obtain highly elective ionophores for lithium ions. The new ionophore was compared with previously reported ionophores under similar measurement conditions with the same plasticizer, tris(2-ethylhexyl) phosphate in poly(vinyl chloride)(PVC) membrane electrodes. Separate solution method was used to determine relative selectivity coefficients for the electrode. The selectivity coefficients($K_{LiM}^{POT}$) of lithium over ammonium, alkali and alkaline earth metal ions go from about $2.4{\times}10^{-1}$ to $2.3{\times}10^{-4}$ to working range and pH dependence have also been studied.

• Analytical Science and Technology
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• v.9 no.3
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• pp.292-301
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• 1996

The synthesis of poly(ether)tailed bipyridine complex as redox reaction probes has advanced attempts to interpret very slow diffusion and heterogeneous electron transfer. Diffusion coefficients as low as $1.5{\times}10^{-15}cm^2/s$ have been observed for the oxidation of neat $Co(bpy(ppgm)_2)_{3^-}(ClO_4)_2$ with $LiClO_4$ electrolyte. Heterogeneous electron transfer rate constants of materials were found to vary with diffusion coefficient. The decrease in k as the diffusion coefficient decreases was actually caused by the decreasing D. Diffusion coefficient for compound of strong ion pairing anion($ClO{_4}^-$) was much smaller than the diffusion coefficient for compound of weak ion pairing anion($CF_3COO^-$).

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.154-160
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• 1997

The interaction between pyronine G(PG) and surfactants has been examined by the absorption and fluorescence spectroscopy. The optimum condition for ${\gamma}$-band in PG-AOT system was found when S/D(concentration of surfactant / concentration of PG) was in the vicinity of 80. The disassociation of stacking conformation occured gradually at S/D>80. In PG-cationic and nonionic surfactant systems the absorptivity of monomeric PG increased. With the increment of the concentration of NaCl in PG-AOT system, the absorptivity of ${\gamma}$-band decreased at S/D<10 but, increased remarkably at S/D>20. PG-AOT system with the addition of NaCl showed greater dissociation than that without the addition of NaCl.