• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1159-1164
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• 1999

The study investigated the effect of carrier composition (ionic strength and pH) on the retention of various proteins in flow field-flow fractionation (Flow FFF) as well as the conformational change of Bovine Serum Albumin (BSA) with urea concentration, storage time and temperature. The study found that the retention of protein in Flow FFF increased with the ionic strength of the carrier liquid. Most proteins were well solubilized at pH = 7-8. The hydrodynamic diameters obtained from Flow FFF retention data agree well with theoretical values. The retention increased and the peak shape became distorted at extreme pH conditions of the carrier solution. The selected carrier composition for comparison between the literature value of proteins was 0.05 M tris buffer solution with a pH of 8. Storing BSA at 4 ±2℃ over a period of three months resulted in slow dimerization. Also, in case of the storage of BSA at 37 ±5℃ for one week, the retention of both BSA monomer and dimer increased with the urea concentration. Finally, the structural composition of specific enzymes: malonyl-CoA decarboxylase (MCDC) and malonyl-CoA synthesis (MCS) was determined by using Flow FFF at specific carrier solutions. The molecular weight of the natural MCDC was determined to be 208 kDa, which means it is a homotetramer, while that of the MCS was determined to be 47 kDa, which means it is a monomer.

• Applied Chemistry for Engineering
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• v.20 no.3
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• pp.313-316
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• 2009

Synthesis of porous $CeO_2$ particles was investigated using various ionic liquids (ILs) as an effective template. The pore structure and crystalline phase of $CeO_2$ particles was affected significantly by the composition of ionic liquids. The strength of the hydrogen bonds on the anion part of ionic liquid was an essential factor to form the pore architecture of $CeO_2$ particles. Moreover, the length of alkyl group on the cation part of ionic liquid determined the pore size and surface area of $CeO_2$ particles. Among the ionic liquids, it was found that 1-Buthyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) was the most effective ionic liquid to synthesize the porous $CeO_2$ particle.

• Economic and Environmental Geology
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• v.53 no.4
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• pp.347-362
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• 2020

Iron (hydro)oxides in aqueous environments are primarily formed due to mining activities, and they are known to be typical colloidal particles disturbing surrounding environments. Among them, hematites are widespread in surface environments, and their behavior is controlled by diverse factors in aqueous environments. This study was conducted to elucidate the effect of environmental factors, such as ionic composition and strength, pH, and natural organic matter (NOM) on the behavior of colloidal hematite particles. In particular, two analytical methods, such as dynamic light scattering (DLS) and single-particle ICP-MS (spICP-MS), were compared to quantify and characterize the behavior of colloidal hematites. According to the variation of ionic composition and strength, the aggregation/dispersion characteristics of the hematite particles were affected as a result of the change in the thickness of the diffuse double layer as well as the total force of electrostatic repulsion and van der Walls attraction. Besides, the more dispersed the particles were, the farther away the aqueous pH was from their point of zero charge (PZC). The results indicate that the electrostatic and steric (structural) stabilization of the particles was enhanced by the functional groups of the natural organic matter, such as carboxyl and phenolic, as the NOM coated the surface of colloidal hematite particles in aqueous environments. Furthermore, such coating effects seemed to increase with decreasing molar mass of NOM. On the contrary, these stabilization (dispersion) effects of NOM were much more diminished by divalent cations such as Ca²⁺ than monovalent ones (Na⁺), and it could be attributed to the fact that the former acted as bridges much more strongly between the NOM-coated hematite particles than the latter because of the relatively larger ionic potential of the former. Consequently, it was quantitatively confirmed that the behavior of colloidal hematites in aqueous environments was significantly affected by diverse factors, such as ionic composition and strength, pH, and NOM. Among them, the NOM seemed to be the primary and dominant one controlling the behavior of hematite colloids. Meanwhile, the results of the comparative study on DLS and spICPMS suggest that the analyses combining both methods are likely to improve the effectiveness on the quantitative characterization of colloidal behavior in aqueous environments because they showed different strengths: the main advantage of the DLS method is the speed and ease of the operation, while the outstanding merit of the spICP-MS are to consider the shape of particles and the type of aggregation.

• Membrane Journal
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• v.24 no.3
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• pp.231-239
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• 2014

Polyetherimide (PEI) membranes for separators in Zn air batteries were prepared via phase inversion process from casting solution composed of PEI, n-methylpyrolidone (NMP), and polyvinylpurrolidone (PVP). Furthermore, Zn air batteries were fabricated with the separators. The effects of PEI content and PVP addition in the casting solution on the morphology, mechanical strength, ionic conductivity were investigated through SEM, stress-strain test and ac impedance test. The elelctrochemical performances of the batteries were evaluated through galvanostatic discharge analysis. The mechanical strength of the membrane increased with increasing PEI composition in the casting solution. Little effect of PVP addition into the solution on the mechanical strength of the membrane was investigated. The ionic conductivity value decreased with increasing PEI composition in the solution. With addition of PVP, ionic conductivity of membrane increased until 10 wt% to show the maximum value of 0.1 S/cm. In the higher range of PVP addition over 10%, the ionic conductivity decreased with increasing PVP addition. Ionic conductivity of separator strongly affected the capacity of Zn air battery, and the battery assembled with the separator which showed high ionic conductivity showed high capacity.

• Journal of Bio-Environment Control
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• v.9 no.2
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• pp.79-84
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• 2000

The growth and quality differences between common thyme(Thymus vulgaris L.) and lemon thym (Thymus$\times$citriodorus) were investigated. They were grown in a hydroponics culture system (DFT) with a nutrient solution developed by the European Vegetable R&D Center in Belgium. Nutrient solution ionic strength used were 1.2, 2.4, 4.8 and 7.2 mS.cm-1. The dry matter of two thymes were increased with increasing ionic strength, while shoot length, root length and fresh weight were decreased. Chlorophyll content was higher in lemon thyme, while vitamin C content and essential oil content were higher in common thyme. The essential oil content showed a similar trend as those of growth. The main compostion of essential oil were thymol and carvacrol in common thyme, and geraniol and $\alpha$-citral in lemon thyme. The highest content of these compounds was obtained in 1.2mS.cm-1 treatment. Consequently, the ionic strength of 1.2mS.cm-1 was suitable for the production of quality thymes.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.575-581
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• 1997

UDs were synthesized from two different polyols(PTMG, PBEAG), ionic chain extender(DMPA), EDA with $H_{12}-MDI$. PU/PMMA hybrids were prepared with free radical polymerization of MMA monomer in MMA-swelled PUD. PUD particle size and film properties were investigated ionic content and polyol type. Mechanical and thermal properties of PU/PMMA hybrid film were studied in terms of PU's ionic content and the venation of PU/PMMA compositions. As DMPA content increased from 2wt% to 10wt% in PUD, particle size of PUD decreased. PUD's particle size with ester type polyol was found to be smaller then ether type polyol used. Phase separation between hard segment(HS) and soft segment(SS) with ionic contents in PU was shown by the thermal, mechanical property measurement. Although the composition of MMA was changed from 0 to 40 wt% in PU/PMMA hybrid, the particle size of the hybrid did not increase. Using the ester type polyol, tensile strength of hybrid was found to increase by 2wt% - 6wt% DPMA content, but as higher content the strength of hybrid decreased. Moreover with the ether type polyol, tensile strength of hybrid was observed to increase by 2wt% - 4wt% DMPA content, while decreasing at higher content. PU and PMMA polymer molecule being mixed in molecular level was confirmed from the pattern of $T_g$ in DSC thermogram.

• Analytical Science and Technology
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• v.16 no.2
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• pp.159-165
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• 2003

To develop an ionic equilibria model applicable to the sulfuric acid leaching solutions of zinc oxide ore, the method of the Pitzer equation and that of the Vasil'ev equation were compared. As the ionic strength of the solution increased to 9 m, the results of ionic equilibria by the Pitzer equation were more accurate than those by Vasil'ev. To simulate the sulfuric acid leaching solutions of zinc oxide ore, the mixed solutions with the various composition of $ZnSO_4-Fe_2(SO_4)_3-Na_2SO_4-H_2SO_4-NaOH-H_2O$ were prepared. The pH values calculated in this study agreed well with those measured at $25^{\circ}C$.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.6
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• pp.818-829
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• 2013

The collection of rainwater samples was made at Jeju area during 2009~2010, and the major ionic species were analyzed. In the comparison of ion balance, conductivity, and acid fraction for the validation of analytical data, the correlation coefficients showed a good linear relationship within the range of 0.966~0.990. The volume-weighted mean pH and electric conductivity were 4.9 and $17.8{\mu}S/cm$, respectively, at the Jeju area. The volume-weighted mean concentrations of ionic species in rainwater were in the order of $Cl^-$ > $Na^+$ > $nss-SO_4{^{2-}}$ > $NH_4{^+}$ > $NO_3{^-}$ > $Mg^{2+}$ > $H^+$ > $nss-Ca^{2+}$ > $HCOO^-$ > $K^+$ > $PO_4{^{3-}}$ > $CH_3COO^-$ > $NO_2{^-}$ > $F^-$ > $HCO_3{^-}$ > $CH_3SO_3{^-}$. The ionic strength of rainwater was $0.26{\pm}0.21$ mM during the study period. The composition ratios of ionic species were such as 50.1% for the marine sources ($Na^+$, $Mg^{2+}$, $Cl^-$), 30.9% for the anthropogenic sources ($NH_4{^+}$, $nss-SO_4{^{2-}}$, $NO_3{^-}$), and 4.7% for the soil source ($nss-Ca^{2+}$), and 3.1% for organic acids ($HCOO^-$, $CH_3COO^-$). From the seasonal comparison, the concentrations of $NO_3{^-}$, $nss-Ca^{2+}$, and $nss-SO_4{^{2-}}$ increased in winter and spring seasons, indicating a reasonable possibility of long range transport from Asia continent. Especially, the acidifying contributions by major inorganic acids ($nss-SO_4{^{2-}}$ and $NO_3{^-}$) and organic acids ($HCOO^-$ and $CH_3COO^-$) were 87.6% and 12.4%, respectively. In comparison by sectional inflow pathway of air mass during the rainy sampling days, the concentrations of $nss-SO_4{^{2-}}$ and $NO_3{^-}$ were relatively high when the air mass was moved from the China continent into Jeju area.

• Journal of the Korean Chemical Society
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• v.10 no.3
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• pp.114-118
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• 1966

The glass electrode was empirically calibrated in dioxane-and ethanol-water mixed solvents, by means of which the pH-meter reading could be converted to stoichiometric hydrogen ion concentration. By the potentiometric titration method, the thermodynamic dissociation constants of hydrogen cupferrate (HCup) with variations of ionic concentration in aqueous solution were determined, and by the extrapolation of the constants the new thermodynamic $pK_a$ value, 3.980${\pm}$0.006, at zero ional concentration was obtained. The thermodynamic dissociation constants of HCup in dioxane-and ethanol-water solution were also potentiometrically determined with the changes in composition of organic solvents at 0.01 and 0.05 of the ionic strength(${mu}$) and 25 $^{\circ}C$. The empirical formula of the constants with mole fraction(n) of the organic solvent are as follow: Dioxane-water solution. $pK_a$= 12.96n + 4.10 at ${\mu}$ = 0.01, n = 0.0228∼0.171 $pK_a$= 12.05n + 4.23 at ${\mu}$ = 0.05, n= 0.0228∼0.171 Ethanol-water solution, $pK_a$= 4.0ln + 4.26 at ${\mu}$= 0.01, n= 0.0395∼0.262 $pK_a$= 3.83n + 4.34 at ${\mu}$= 0.05, n= 0.0395∼0.262

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.129.2-129.2
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• 2010

AEM which were used for solid alkaline fuel cell(SAFC) were prepared by photo polymerization in method pore-filling with various quaternary ammonium cationic monomers and crosslinkers without an amination process. Their specific thermal and chemical properties were characterized through various analyses and the physico-chemical properties of the prepared electrolyte membranes such as swelling behavior, ion exchange capacity and ionic conductivity were also investigated in correlation with the electrolyte composition. The polymer electrolyte membranes prepared in this study have a very wide hydroxyl ion conductivity range of 0.01 - 0.45S/cm depending on the composition ratio of the electrolyte monomer and crosslinking agent used for polymerization. However, the hydroxyl ion conductivity of the membranes was relatively higher at the whole cases than those of commercial products such as A201 membrane of Tokuyama. These pore-filling membranes have also excellent properties such as smaller dimensional affects when swollen in solvents, higher mechanical strength, lowest electrolyte crossover through the membranes, and easier preparation process compared of traditional cast membranes. The prepared membranes were then applied to solid alkaline fuel cell and it was found comparable fuel cell performance to A201 membrane of Tokuyama.