• Membrane Journal
• /
• v.18 no.3
• /
• pp.234-240
• /
• 2008

This work demonstrates the preparation of proton conducting crosslinked polymer electrolyte membranes by blending polystrene-b-poly(hydroxyethyl acrylate) (PS-b-PHEA) and poly(vinyl alcohol) (PVA) at 1 : 1 wt ratio. The PHEA block of the diblock copolymer was crosslinked with PVA using sulfosuccinic acid (SA) via the esterification reaction between -OH of membrane and -COOH of SA, as confirmed by FT-IR spectroscopy. Ion exchange capacity (IEC) continuously increased from 0.14 to 0.91 meq/g with increasing concentrations of SA, due to the increasing portion of charged groups in the membrane. In contrast, the water uptake increased up to 20.0 wt% of SA concentration above which it decreased monotonically. The membrane also exhibited a maximum proton conductivity of 0.024 S/cm at 20.0 wt% of SA concentration. The maximum behavior of water uptake and proton conductivity is considered to be due to competitive effect between the increase of ionic sites and the crosslinking reaction according to the SA concentration.

• Membrane Journal
• /
• v.16 no.4
• /
• pp.241-251
• /
• 2006

In this study, crosslinked copolyimides with random (r-) and block (b-) structure were fabricated using N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid and pentanediol as crosslinkers. Linear r- and b-sulfonated copolyimides were also fabricated for comparison. Ion exchange capacities of r- and b-copolyimides were very similar to each other owing to their strong dependence of sulfonic acid content. The physical crosslinking via dimerization of carboxylic acid groups induced a reduced average interchain distance in b-copolyimide without crosslinkers. Consequently, its water uptake and methanol permeability were lower than those of r-sulfonated copolyimides. Simultaneously, the reduced interchain distance increased the content of fixed-charged ions per unit volume. The high fixed-charged ion density contributed to an enhancement of proton conductivity In the b-sulfonated copolyimide. Crosslinking caused the reduction of average interchain distance between polymer chains irrespective of types of crosslinker and polymer structure, leading to low methanol permeability. On the contrary, their proton conductivity was improved owing to formation of effective hydrophilic channels responsible for proton conduction. In particular, this trend was observed in r-copolyimide containing a fixed charged ion.

• Korean Journal of Mineralogy and Petrology
• /
• v.36 no.2
• /
• pp.117-124
• /
• 2023

X-ray diffraction analysis, X-ray fluorescence analysis, thermal differential and thermos gravimetric analysis, cation exchange capacity analysis, and Cesium (Cs), Strontium (Sr) adsorption experiments were performed to investigate the physical and chemical properties of natural zeolite from Guryongpo in Korea. As a result of X-ray diffraction analysis, minerals such as mordenite, heulandite, clinoptilolite, and illite are contained, and as a result of X-ray fluorescence analysis, elements such as SiO₂, Al₂O₃, CaO, K₂O, MgO, Fe₂O₃ and Na₂O are contained, and the cation exchange capacity was 148.6 meq/100 g. As a result of thermal differential and thermos gravimetric analysis, it was confirmed that the thermal stability was excellent up to 600 ℃. As a result of the adsorption equilibrium experiment over time, the equilibrium was reached within 30 min. for Cesium (Cs) and within 8 hr. for Strontium (Sr), and the adsorption rates of Cesium (Cs) and Strontium (Sr) were 80% and 18%, respectively. As a result of the single-component isothermal adsorption experiment, in conformed to the Langmuir model, and the maximum Cesium (Cs) adsorption amount was 131.5 mg/g, which was high, while the Strontium (Sr) maximum adsorption amount was 29.5 mg/g, which was low. In the case of the natural zeolite used in this study, the content of minerals including 8-rings such as clinoptilolite, heulandite, and mordenite is high, showing high selectivity for Cesium (Cs).

• Membrane Journal
• /
• v.18 no.4
• /
• pp.261-267
• /
• 2008

A graft copolymer consisting of poly(vinyl chloride) (PVC) backbone and poly(hydroxyethyl acrylate) (PHEA) side chains was synthesized via atom transfer radical polymerization (ATRP). Direct initiation of the secondary chlorines of PVC facilitates grafting of hydrophilic PHEA monomer. This graft copolymer, i.e. PVC-g-PHEA was cross-linked with sulfosuccinic acid (SA) via the esterification reaction between -OH of the graft copolymer and -COOH of SA, as confirmed by FT-IR spectroscopy. Ion exchange capacity (IEC) continuously increased to 0.87meq/g with increasing concentrations of SA, due to the increasing portion of charged groups in the membrane. However, the water uptake increased up to 20.0wt% of SA concentration above which it decreased monotonically. The membrane also exhibited a maximum proton conductivity of 0.025 S/cm at 20.0 wt% of SA concentration, which is presumably due to competitive effect between the increase of ionic sites and the crosslinking reaction.

• Journal of the Mineralogical Society of Korea
• /
• v.28 no.4
• /
• pp.299-308
• /
• 2015

The six natural zeolites collected in Pohang area, Kyungsangbuk-do, Korea, were characterized by XRD, XRF, DTA, TGA, and CEC analysis. The primary species of these zeolite are modenite, albite, and quarts in Kuryongpo-A (Ku-A), Kuryongpo-B (Ku-B), Kuryongpo-C (Ku-C), Donghae-A (Dh-A), Donghae-B (Dh-B), and Donghae-C (Dh-C) samples. The XRF analysis showed that the six zeolites contain Si, Al, Na, K, Mg, Ca, and Fe. Cation exchange capacity of Kuryongpo-C (Ku-C) zeolite was the highest compared to other zeolites. The capabilities of removing heavy metal ions such as $Pb^{2+}$, $Cd^{2+}$ and $Cu^{2+}$ were compared. The effect of reaction time in removing heavy metal ions was studied. The experimental results showed that the efficiency of removal was low for $Pb^{2+}$, $Cd^{2+}$ and $Cu^{2+}$ ions. These may be caused by the low content of zeolite in the six natural zeolites. This indicates that the adsorption capacity roughly tends to depend on the zeoite contents, ie., the grade of zeolite ore.

• Korean Journal of Materials Research
• /
• v.5 no.8
• /
• pp.1035-1039
• /
• 1995

Synthetic zeolite was prepared by using of natural bentonite from Kampo area and the application of detergent builder was investigated. The optimum synthetic condition was SiO$_2$/Al$_2$O$_3$= 2, Na$_2$O/A1$_2$O$_3$=1, H$_2$O/A1$_2$O$_3$=30 at 90$^{\circ}C$ for 3hr and it was found by XRD analysis that the zeolite synthesized under this condition was type A. When the zeolite A synthesized under the optimum condition was contacted with 40$^{\circ}$Dh CaCl$_2$solution at 30$^{\circ}C$ for 15min, the cation exchange capacity was 264.9mg CaO/g-zeolite. And the whiteness of the sample was 89% and the mean particle size was 9.95$\mu\textrm{m}$.

• Transactions of the Korean hydrogen and new energy society
• /
• v.22 no.1
• /
• pp.60-68
• /
• 2011

[ $ZrO_2-TiO_2$ ]binary oxides with various Zr:Ti molar ratios were prepared by sol-gel method and Nafion$^{(R)}$/$ZrO_2-TiO_2$ composite membranes were fabricated for proton exchange membrane fuel cells (PEMFCs) at high temperature and low humidity. Water uptake, Ion exchange capacity (IEC), and proton conductivity of Nafion$^{(R)}$/$ZrO_2-TiO_2$ composite membranes were characterized and these composite membranes were tested in a single cell at $120^{\circ}C$ with various relative humidity (R.H.) conditions. The obtained results were compared with the unmodified membranes (Nafion$^{(R)}$ 112 and Recast Nafion$^{(R)}$). A Nafion$^{(R)}$/$ZrO_2-TiO_2$ composite membrane with 1:3 of Zr:Ti molar ratio showed the highest performance. The performance showed 500 mW/$cm^2$ (0.499V) at $120^{\circ}C$, 50% R. H., and 2 atm.

• Journal of the Mineralogical Society of Korea
• /
• v.16 no.4
• /
• pp.295-305
• /
• 2003

This study aims to provide the physicochemical properties of three kinds of organo­smectites which can be diversely used in industries. Some properties of them were compared with Na­smectite. Three kinds of organo­smectites such as Hexadecyltrimethylammonium(HDTMA), Benzyldimethyltetradecylammonium(BDTDA), and Cetylpyridinium(CP) exchanged smectites were manufactured for this study. Three types of organo­smectites showed the alkaline character(pH 9), very low swelling property and viscosity, and a fast flocculation behavior because of strong hydrophobic property in contrast to hydrophilic Na­smectite. Three organo­smectites showed the strong interlayer expansion with basal spacing from $19\AA$ to $23\AA$ compared with the Na­smectite of about 12 $\AA$. Organic cations such as HDTMA, BDTDA, and CP exchanged into smectite were completely decomposed in the temperature range from $250^{\circ}C$ to $400^{\circ}C$. Generally, three organo­smectites showed the similar mineralogical, physicochemical and thermal properties. But their properties are quite different from Na­smectite. Considering economically, CP exchanged smectite would be used for the diverse utilization field in the future time.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.1
• /
• pp.33-42
• /
• 2000

Adsorption onto the surfaces of solid particles is a well known phenomenon that causes the retardation effect of heavy metals in soils. For adequate remediation of soil and groundwater contamination, it is important to investigate the mobility of heavy metals that largely depends on pH conditions in the soil water since adsorption of heavy metals is pH-dependent. In this study, we investigated the transport of Zn ion under various pH conditions in a sandy soil by conducting batch and column tests. The batch test was performed using the standard procedure of equilibrating fine fractions collected from the soil with eleven different initial $ZnCl_2$ concentrations, and analysis of Zn ion in the equilibrated solutions using ICP-AES. The column test consisted of monitoring the concentrations of soil solutions exiting the soil column with time known as a breakthrough curve (BTC). We injected respectively $ZnCl_2$ and KCl solutions with the concentration of 10 g/L as a tracer in a square pulse type under three different pH conditions (7.7, 5.8, 4.1) and monitored the flux concentration at the exit boundary using an EC meter and ICP-AES. The resident concentration was also monitored at the 10cm-depth by Time Domain Reflectometry (TDR). The results of batch test showed that ion exchange process between Zn and other cations (Ca, Mg) was predominant. The retardation coefficients obtained from adsorption isotherms (Linear, Freundlich, Langmuir) resulted in the various values ranging from 1.2 to 614.1. No retardation effect but ion exchange was found for the BTCs under all pH conditions. This can be explained by the absence of other cations to desorb Zn ion from soil exchange sites under the conditions of ETC experiment imposing blank water as leachate in steady-state flow. As pH decreased, the peak concentration of Zn increased due to the competition of Zn with hydrogen ions ($H^+$) and the concentrations of other cations decreased. The peak concentration of Zn was increased by 12.7 times as pH decreased from 7.7 to 4.1.

• Journal of the Mineralogical Society of Korea
• /
• v.27 no.1
• /
• pp.41-51
• /
• 2014

The four natural zeolites collected in Pohang and Gyeongju area, Kyungsangbuk-do, Korea, were characterized by XRD, XRF, DTA, TGA, and CEC analysis. The primary species of these zeolite are heulandite, modenite, illite, and illite in Kuryongpo (Ku), Pohang (Po), Yangbuk-A (Ya-A), and Yangbuk-B (Ya-B) samples. The XRF analysis showed that the four zeolites contain Si, Al, Na, K, Mg, Ca, and Fe. Cation exchange capacity of Kuryongpo (Ku) zeolite was the highest compared to other zeolites. The adsorption capacities of Cs and Sr in the four natural zeolites were compared at $25^{\circ}C$. On the basis of adsorption data Langmuir and Freundlich adsorption isotherm model were confirmed. The equilibrium process was descried well by Langmuir isotherm model. This study shows that Ya-A zeolite is the most efficient for the $Cs^+$ and $Sr^{2+}$ ion adsorption compared to the other natural zeolites.