• Membrane Journal
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• v.28 no.6
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• pp.388-394
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• 2018

Carbon nanotube (CNT) based membranes are promising candidates for separation membranes by showing high water transport rate and ion rejection rate according to their radii. The ion selectivity is an important factor to discover the full potential of CNT membranes, and it is affected by the functionalization of CNTs. With multivalent/size ion mixtures, the ion selectivity is affected by not only ion-functional groups interaction but also ion-ion interactions and ion size exclusion in a complex manner. In this study, molecular dynamics simulations are performed to study the ion selectivity of functionalized carbon nanotubes when multivalent/size ions are contained. The permeation energy barriers are calculated by plotting potential of mean force profiles, and various factors, such as CNT size and partial charges, affecting ion selectivity are investigated. The results presented here will be useful for designing CNT membranes for ion separation, biomimetic ion channels, etc.

• Bulletin of the Korean Chemical Society
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• v.25 no.10
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• pp.1465-1470
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• 2004

A short and efficient synthesis, solvent extraction and potentiometric measurements of new thiazole-containing naphtho-crown ethers are reported. The naphthalene moiety enhances the ammonium ion selectivity over potassium ion. The selectivity of ${NH_4}^+/K^+$ follows the trend $3\;{\approx}\;2\;>\;1$, indicating that the differences in conformational changes of 2 and 3 in forming ammonium complexes affect little on the resulting ammonium/potassium extraction selectivity ratio. The ammonium ion-selective electrodes were prepared with noctylphenyl ether plasticized poly(vinyl chloride) membranes containing 1-4 the effect of one naphthalene unit introduced on either right (2) or left (3) side of thiazolo-crown ether on their potentiometric properties (e.g., ammonium ion selectivity over other cations, response slopes, and detection limits) were not apparent. However, the ammonium ion selectivity of 1, 2 and 3 over other alkali metal and alkaline earth metal cations is 10-100 times higher than that of nonactin.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.3
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• pp.194-197
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• 2002

Ion exchange is a chemical reaction between the ions in solution phase and ions in solid phase and is widely used in softening, demineralization, removal and collection of specific ions, and ion migration in the ground water. The ion selectivity depends on the charge and the hydrated radius of ion. The objective of this study was to examine the applicability of anion selectivity obtained from the ion exchange equilibrium OH/sup -/ < F/sup -/ < HCO/sup -/ < Cl/sup -/ < Br/sup -/ ≤ NO₃/sup -/ < SO₄/sup 2-/ to the column ion exchange. The column ion exchange was facilitated in the lower charge of counter-ion in the background electrolyte.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.2
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• pp.156-159
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• 2002

Ion exchange is the most reliable process to remove the ionic impurities and the economic operation. ion exchange is widely used in water and wastewater treatment, especially softening and demineralization. ion selectivity depends on the hydrated radius, charge of ions and concentration. The objective of this study was to determine the selectivity order of cations with equilibrium and column ion exchanges and to investigate the effect of the background anion on selectivity. Cation selectivity increases with decreasing concentration and increasing charge ( $H^+$ < $K^+$ << $Cu^{2+}$ < $Co^{2+}$ < TEX>$Ca^{2+}$ << $Ce^{3+}$)in equilibrium and column cation adsorptions.

• Journal of Environmental Science International
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• v.16 no.8
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• pp.907-912
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• 2007

Ion exchange resin was used to remove silica ion at ultralow concentration. The effects of temperature, type of ion exchange resin and single/mixed-resin systems on removal efficiency were estimated. As temperature increased, the slope of concentration profile became stiff, and the equilibrium concentration was higher. In the single resin system, the removal of silica was continued up to 400 min, but the silica concentration was recovered to initial concentration after 400 min due to the effect of dissolved $CO_2$. In the mixed-resin system it took about 600 min to reach equilibrium. Because of faster cation exchange reaction than anion exchange reaction, the effect of $CO_2$ could be removed. Based on the experimental results carried out in the mixed-resin system, the selectivity coefficients of silica ion for each ion exchange resin were calculated at some specific temperatures. The temperature dependency of the selectivity coefficient was expressed by the equation of Kraus-Raridon type.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.1
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• pp.121-128
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• 2013

The concern for dissolved phosphate in water/wastewater has been increasing because of the risk for eutrophication. A variety of conventional and advanced technologies were applied to meet the enforced new regulation of phosphate around the world. However, there still remained a lot of challenge because most introduced/developed method, for example, biological and physic-chemical treatment is not easy to satisfy the new regulation of phosphate in water. In order to meet the new regulation, the application of ion exchanger has been tried which showed that the removal efficiency for phosphate was strongly determined by in the presence of the competing ion, especially sulfate. As results, a new class of ion exchanger governed by ligand exchange was developed and investigated to increase the selectivity for phosphate. The current study using organic/inorganic anion exchanger developed with Lewis acid-base interaction confirms the selectivity for phosphate over sulfate. According to isotherm test and column test, the value of the maximum phosphate uptake (Q) showed 64 mg/g as $po{_4}^{3-}$ and the breakthrough for phosphate occurs after 1000 min and completely finishes at 2500 min, respectively.

• Journal of the Korean Chemical Society
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• v.45 no.1
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• pp.31-39
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• 2001

Newly synthesized 15-Crown-5 derivatives including anthracene were used as neutral carriers for ion selective electrodes to determine potassium ion by potentiometry. Among the five neutral carriers studied in this work, N-(4'-benzo-15-crown-5-ether)-anthracene-9-imine was found to be the best in terms of selectivity and stability. The optimal composition of ion selective membrane was 1.0, 33.0 and 66.0 wt% for neutral carrier, PVC and plasticizer, resperctively. Addition of KTpCIPB used as a lipophilic additive improved the Nernst slope and the selectivity of potassium ion over alkali and alkaline earth metals. Especially, the selectivity of potassium ion over ammonium ion was remarkably good ($logK^{pot}_(K^+,NH_4^+}$=-2.59). The response time was also excellent ($t_{100}$=5sec) and continuous use of this electrode for three weeks has not changed the selectivity and analytical characteristics.

• Analytical Science and Technology
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• v.18 no.6
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• pp.491-494
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• 2005

The main component governing selectivity in ion-selective electrodes and optodes is the ionophore. For this reason, a member of natural products that possess selective ion-binding properties have long been sought after. By applying this principle, the performance of cyclosporin used as neutral carriers for calcium selective polymeric membrane electrode was investigated. The calcium ion-selective electrode based on cyclosporin gave a good Nernstian response of 26.6 mV per decade for calcium ion in the activity range $1{\times}10^{-6}M$ to $1{\times}10^{-2}M$. The optimized calcium ion-selective electrode displayed very comparable selectivity for $Ca^{2+}$ ion against alkali and alkaline earth metal ions, $Na^{2+}$, and $Mg^{2+}$ in particular.

• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.36-36
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• 2001

Small conductance $Ca^{2＋}$-activated $K^{+}$ channels (or S $K_{Ca}$ channels) are a group of $K^{＋}$-selective ion channels activated by sub-micromolar concentrations of intracellular $Ca^{2＋}$ independent of membrane voltage. We expressed a cloned S $K_{Ca}$ channel, rSK2, in Xenopus oocytes and investigated the monovalent cation selectivity of the channels. We have used site-directed mutagenesis and macro-channel recordings to identify amino acid residues influencing the ion selectivity.(omitted)d)

• Journal of Environmental Science International
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• v.21 no.12
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• pp.1449-1454
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• 2012

The ion selective microelectrodes (ISME) have been applied to observe the continuous profiles of NO3-N and NH4-N in bulk solutions or biofilms. In order to evaluate the performance and applicability of ion concentration measuring system, the characteristics, such as slope of calibration curve, detection limit and potentiometric selectivity coefficient were investigated. The slopes of calibration curve showed high degree of correspondence for each target ion concentrations. And the detection limits of nitrate and ammonia ion selective microelectrode were 10-4.7 M and 10-4.4 M, respectively. These ion selective microelectrodes were proved that their own performance could be maintained for 16 days after making. NO3-N and NH4-N selective microelectrodes were also adapted to detect the continuous ion profiles of cilia media packed MLE (Modified Ludzack-Ettinger) process. And the monitored nitrate and ammonia ion profiles with the ion selective microelectrode were stable and well corresponded to the results with conventional ion chromatograph. However, the electric potential was unstable until 8 hr because of the unknown noise. The tip shape and performance of the ion selective microelectrode was stably kept over 2 days continuous monitoring.