• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.127-138
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• 1994

In the process of pervaporation separation for aqueous ethanol solution through cellulose tai-acetate(CTA) membrane, the modelling on the solution-diffusion permeation mechanism was built up on the basis of sorption and permeation experimental results. Also its function type and parameter were examined. The composition of sorption equilibrium in three component system(Ethanol/Water/CTA) were compared with the calculated value by Flory-Huggins' equation using the pure component sorption data. In order to apply the thermodynamic equilibrium relationship between the membrane free composition in the membrane and the equilibrium composition in the liquid phase, the apparent activity this system, however, the results were not satisfied. Diffusion equations were expressed with the concentration gradient considering permeate alone, and a concentration-dependent diffusion coefficient which includes a parameter was used. And this model was fitted with the measured permeation rates. If the permeation rate and the amount of sorption of one component were much larger than those of the other, the bulk flow term could not be negligible. The flux and selectivity were increased with increasing temperature, and with decreasing downstream pressure.

• Analytical Science and Technology
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• v.8 no.2
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• pp.161-166
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• 1995

Determination of acteoside in Pedicularis resupinata var. oppositifolia has been studied using ion pair liquid chromatography. Sample was extracted with 40mL methanol for 4 hrs. The extract was cleaned up by using Sep-Pak $C_{18}$ catridge and 8mL aqueous methanol eluent(methanol 50%, water 50%, phosphate buffer pH=8.0). Its determination was performed by means of IP-HPLC with a Hamilton PRP-1 polystyrene-divinylbenzene reversed phase column($15cm{\times}4.6mm$ i. d., $5{\mu}m$) and an aqueous methanol eluent(methanol 60%, water 40% phosphate buffer pH=8.2) containing of $5.0{\times}10^{-3}M$ tetrabutylammonium bromide. The established method was applied to the sample that was collected in area of Pyung Chang gun. As a result, its content ranges showed to be 0.062~0.076%.

• Membrane Journal
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• v.8 no.3
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• pp.138-147
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• 1998

This paper compared selectivities and mass transfer rates of valuable aromatics (naphthalene group: carbon number 10-12) in the light cycle oil obtained from solvent extraction (SE) with those obtained from liquid membrane permeation (LMP). An aqueous solution of dimethylsulfoxide (DMSO) and an aqueous solution of saporrin and DMSO were used as extraction solvent of SE and the membrane phase of LMP, respectivdy. Selectivities of naphthalene group in reference to n-nonane obtained from SE runs were rapidly increased with decreasing the operating temperature, whereas, those obtained from LMP runs were remained constant throughout the operating temperature. At room temperature, selectivities of naphthalene group obtained from SE were greater than those from SE. Furthermore, mass transfer rates of naphthalene group by SE and LMP were measured in a baffled batch stirred vessel. It was found that the extraction rates of SE were faster by about 280 times than the permeation rates of LMP.

• Macromolecular Research
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• v.16 no.2
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• pp.139-148
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• 2008

Biodegradable and elastic poly(L-lactide-co-$\varepsilon$-caprolactone) (PLCL) was electrospun to prepare nanofibers, and N-isopropylacrylamide (NIPAAm) was then grafted onto their surfaces under aqueous conditions using $^{60}Co-{\gamma}$ irradiation. The graft yield increased with increasing irradiation dose from 5 to 10 kGy and the nanofibers showed a greater graft yield compared with the firms. SEM confirmed that the PLCL nanofibers maintained an interconnected pore structure after grafting with NIPAAm. However, overdoses of irradiation led to the excessive formation of homopolymer gels on the surface of thc PLCL nanofibers. The equilibrium swelling and deswelling ratio of the PNIPAAm-g-PLCL nanofibers (prepared with 10 kGy) was the highest among the samples, which was consistent with the graft yield results. The phase-separation characteristics of PNIPAAm in aqueous conditions conferred a unique temperature-responsive swelling behavior of PNIPAAm-g-PLCL nanofibers, showing the ability to absorb a large amount of water at < $32^{\circ}C$, and abrupt collapse when the temperature was increased to $40^{\circ}C$. In accordance with the temperature-dependent changes in swelling behavior, the release rate of indomethacin and FITC-BSA loaded in PNIPAAm-g-PLCL nanofibers by a diffusion-mediated process was regulated by the change in temperature. Both model drugs demonstrated greater release rate at $40^{\circ}C$ relative to that at $25^{\circ}C$. This approach of the temperature-controlled release of drugs from PNIPAAm-g-PLCL nanofibers using gamma-ray irradiation may be used to design drugs and protein delivery carriers in various biomedical applications.

• Analytical Science and Technology
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• v.32 no.3
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• pp.96-104
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• 2019

Agastache rugosa, known as Korean mint, is a medicinal plant with many beneficial health effects. In this study, a simple and reliable HPLC-UV method was proposed for the quantification of rosmarinic acid (RA) in the aqueous extracts of A. rugosa. RA was selected as a quantification marker due to its easiness in procurement and analysis. The developed method involved chromatographic separation on a $C_{18}$ column ($250{\times}4.6mm$, $5{\mu}m$) at room temperature. The mobile phase consisted of water and acetonitrile both containing 2 % acetic acid and was run at a flow rate of $1mL\;min^{-1}$. The method was validated for specificity, linearity, precision, and accuracy. It was specific to RA and linear in the range of $50-300{\mu}g\;mL^{-1}$ ($r^2=0.9994$). Intra-day, inter-day, and inter-analyst precisions were ${\leq}0.91%\;RSD$, ${\leq}1.40%\;RSD$, and 1.94 % RSD, respectively. Accuracy was 93.3-95.9 % (${\leq}1.21%\;RSD$). The method could be applied to three batches of bulk samples and three batches of lab scale samples, which were found to be $0.64({\pm}0.04)mg\;g^{-1}$ and $0.48({\pm}0.02)mg\;g^{-1}$ for the dried raw materials of A. rugosa. The results show that the proposed method can be used as a readily applicable method for QC of health functional foods containing the aqueous extracts of A. rugosa.

• Economic and Environmental Geology
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• v.53 no.3
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• pp.221-234
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• 2020

We occur together with telluride minerals. Fluid inclusions in the euhedral quartz crystals are mainly aqueous liquid-rich inclusions, which have salinities about 0.18-2.24 wt% NaCl equivalent. Some quartz vein contains aqueous vapor-rich inclusions as well. Homogenization temperatures of the assemblages of the liquid-rich inclusions are about 141-384 ℃, and the temperatures are lower at the shallower vein samples. In the high Au-Ag grade depth intervals, relatively deeper fluids have relatively higher salinities and homogenization temperatures, while shallower fluids show somewhat wider ranges. These might indicate that the deep Au-Ag bearing hydrothermal fluids at the Moisan area experienced phase separation as well as mixing with meteoric water by decreasing pressure. Au-Ag precipitation in the Moisan deposit is not associated with pyrite, but pyrite include Au-Ag bearing phase as an inclusion, which might possibly be tellurides or electrum. Au/Ag ratios in the Au-Ag bearing phase do not change with different depth.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1143-1148
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• 2010

We investigated the separation of nitrogen heterocyclic compound (NHC) contained in a model coal tar fraction comprising four kinds of NHC [indole (In), quinoline (Q), iso-quinoline (iQ), quinaldine (Qu)], three kinds of bicyclic aromatic compound (BAC) [1-methylnaphthalene (1MN), 2-methylnaphthalene (2MN), dimethylnaphthalene (DMN) mixture with ten structural isomers (DMNs; regarded as one component)], biphenyl (Bp) and phenyl ether (Pe) by liquid membrane permeation (LMP). A batch-stirred tank was used as the permeation unit. An aqueous solution of saponin and n-hexane were used as the liquid membrane and the outer oil phase, respectively. Yield and selectivity of individual NHC was much larger than that of BAC, Bp and Pe. Increasing the initial mass fraction of the saponin to the membrane solution ($C_{sap,0}$) and the initial volume fraction of O/W emulsion to total liquid in a stirred tank (${\phi}_{OW,0}$) resulted in deteriorating the yield of individual NHC, but increasing the stirring speed (N) resulted in improving the yield of each NHC. With increasing $C_{sap,0}$, the selectivity of each NHC based on DMNs increased. Increasing ${\phi}_{OW,0}$ and N resulted in decreasing the selectivity of individual NHC based on DMNs. At an experimental condition fixed, the sequence of the yield and selectivity in reference to DMNs for each NHC was Q > Qu = iQ > In. Furthermore, we compared LPM method with methanol extraction method in view of the separation efficiency (yield, selectivity) of NHC.

• Journal of the Korean Chemical Society
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• v.52 no.2
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• pp.140-147
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• 2008

.A new approach for a cloud point extraction-electrothermal atomic absorption spectrometric method was used for determining bismuth. The aqueous analyte was acidified with sulfuric acid (pH 3.0-3.5). Triton X-114 was added as a surfactant and natriumdiethyldithiocarbaminat (Na-DDTC) was used as a complexing agent. After phase separation at 50oC based on the cloud point separation of the mixture, the surfactant-rich phasen was diluted using tetrahydrofuran (THF). Twenty microliters (20 L) of the enriched solution and 10 l of 0.1% (w/v) Pd(NO3)2 as chemical modifier were dispersed into the graphite tube and the analyte determined by electrothermal atomic absorption spectrometry. After optimizing extraction conditions and instrumental parameters, a preconcentration factor of 195 was obtained for a sample of only 10 mL. The detection limit was 0.04 ng ml-1 and the analytical curve was linear for the concentration range of 0.04-0.70 ng mL-1. Relative standard deviations were <5%. The method was successfully applied for the extraction and determination of bismuth in water samples.

• Resources Recycling
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• v.28 no.6
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• pp.18-25
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• 2019

In order to recover the cerium contained in the spent nickel metal hydride batteries (NiMH battery), the recovered rare earth complex precipitates from NIMH were converted into rare earth hydroxides through ion exchange reaction to react with NaOH aqueous solution at a reaction temperature of 70 ℃, for 4 hours. Rare earth hydroxides were oxidized by injecting air at 80 ℃ for 4 hours to oxidize Ce³⁺ to Ce⁴⁺. The oxidation rate of cerium was confirmed to be about 25 % through XPS, and the oxidized powder was separated from the rest of the rare earth using the difference in solubility in dilute sulfuric acid. The finally recovered powder has a crystal phase of cerium hydroxide (Ce(OH)₄). The cerium purity of the final product was about 94.6 %, and the recovery rate was 97.3 %.

• Journal of Environmental Science International
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• v.4 no.2
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• pp.223-232
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• 1995

New two macrocyclic compounds using as carriers of liquid emulsion menbrame, have been synthesized. These reuslts provide evidance for the usefulness of the theory in designing the systems. The efficiency of selective transport for heavy metal ions have been discussed from the membrane systems that make use of $SCN^-$,<>,$I^-$,CN- and $Cl^-$ ion as co-anions in source phase and make use of $S_2O_3^{2-}$ and $P_2O_7^{4-}$ ion as receiving phase, respectively. The transport rate of M(II) was highest when a maximum amount of the M(II) in the source phase was present as$Cd(SCN)_2$$(P[SCN^-]= 0.40M)$, $Hg(SCN)_2([SCN^-]=0.40M)$ and Pd(CN)$([CN^-]= 0.40M)$. The Cd(II) and Pb(II) over each competitive cations were well transprted with 0.3M-S2032- and 0.3M-P2O74-, respectively in the receiving phase. Results of this study indicate that two criteria must be met in order to have effective macrocycle-mediated transport in these emulsion system. First one must effective extraction of the $M^{n+}$ into the toluene systems. The effectiveness of this extraction is the greatest if locK for $M^{n+}$macrocycle interaction is large and if the macrocycle is very insoluble in the aqueous phase. Second, the ratio of the locK values (or Mn+-receiving phase ($S_2O_3^{2-}$- or $P_2O_7^{4-}$) to $M^{n+}$-macrocycle (($L_1$이나 $L_2$) interaction must be large enough to ensure quantitative stripping of Mn+(($Cd^{2+}$,$Pb^{2+}$)at the toluene receiving Phase interface. $L_1$(3.5-benzo-10,13,18,21-tetraoxa-1,7,diazabicyclo(8,5,5) eicosan) forms a stable ($Cd^{2+}$ and >,$Pb^{2+}$ complexes and $L_1$ is very insoluble in water and its $Cd^{2+}$ and >,$Pb^{2+}$ complex is considerably less stable than $Cd^{2+}$-(S2O3)22- and $Pd^{2+}-P_2O_7^{4-}$ complexes. On the other hand, the stability of the $Hg^{2+}$)+-$L_1$( complex exceed that of the $Hg^{2+}$- (S2O3)22- and Hg2+-P2O74-, and the distribution coefficient of $L_2$(5,8,15,18,23,26-hexaoxa-1,12- diazabicyclo-(10,8,8) octacosane) is much smaller than that of $L_1$. Therefore, the partitioning of Lr is favored by the aqueous receiving Phase, and little heavy metal ions transport is seen despite the large logK for $Hg^{2+}$+-$L_1$ and $Mn^+$($Cd^{2+}$+, $Pb^{2+}$+ and $Hg^{2+}$)-$L_2$ interactions. Key Words : macrocycles, transport, heavy metal, co-anion, source phase, receiveing, complex separation, interaction, destribution coefficient.