• Applied Biological Chemistry
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• v.33 no.4
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• pp.337-342
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• 1990

The pretense from Halobacterium sp. was purified by ethanol precipitation and gel filtration on Sephadex G-75 and G-100. The purified enzyme was found to be homogeneous by polyacrylamide gel electrophoresis It's specific activity was 364units/mg protein and yield was 14% of the total activity of the culture filtrate. The Km value against casein was determined to be $4.2{\times}10^{-4}M$ by Lineweaver-Burk plot The optimal temperature and pH for the enzyme activity were $35^{\circ}C$ and pH 8.0, respectively. The enzyme was stable from 5.0 to 11.0 at relatively wide range of pH but was inactivated at the temperature above $50^{\circ}C$. $Ca^{2+}$ and $Mg^{2+}$ appeared to react as activators whereas $Fe^{3+},\;Zn^{2+},\;Cu^{2+},\;Hg^{2+}\;and\;Cd^{2+}$ as inhibitors. The enzyme activity reduced with increasing the concentration of NaCl : the apparent activity with 2M NaCl was 65% as compared with that without the salt However the enzyme was unstable without salts : the activity was lost when dialyzed against distilled water for 2hr, whereas maintained against 0.1M solution of $CaCl_2$ for 6hr.

• Journal of the Korea Institute of Building Construction
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• v.16 no.3
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• pp.219-227
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• 2016

Chloride ions ingress continuously in reinforced concrete through pores of it by $Cl^-$. Finally, it causes a localized corrosion of the rebar and then it generates cracks on concrete structures. Recently, new materials removing harmful anions have been developed. Layered double hydroxides(LDHs) has an excellent ability to remove harmful anions because various anions can be adsorbed in the interlayer space between divalent and trivalent cations. Thus, LDHs has been applied in various fields. Especially, LDHs is expected to be effective adsorbent binding chloride ions. In this study, $Ca/Al-NO_3$ and $Mg/Al-NO_3$ LDHs were prepared by using a co-precipitation method. $Ca/Al-NO_3$ and $Mg/Al-NO_3$ LDHs were compared and analyzed by using XRD, SEM analysis. Many nano size hexagonal crystals were observed by SEM. Experiments for binding chloride ions of LDHs were conducted by using potentiometric method. The experimental data were measured every 15 minutes. It was observed that the chloride ion content is reduced by increasing of LDHs mass fraction and the reaction rate of $Mg/Al-NO_3$ is faster than $Ca/Al-NO_3$. In future studies, binding chloride capacity in cement materials will be evaluated based on results of this study.

• Korean journal of applied entomology
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• v.29 no.4
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• pp.244-251
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• 1990

Three viral insecticides were differently formulated with a nuclear polyhedrosis virus isolated from Spdodoptera litura by addition of feeding attractant, anti-precipitate of polyhedra, spreading agent, and UV-protectants. Sucrose was effective for attraction of larval feeding to increase the mortality and for protection of polyhedra from inactivation by sunlight when added 1% to 5% of sucrose solution to the formulations. Contents of additives to the formulations were 0.5% in polyvinyl alcohol to prohibit the precipitation of polyhedra and 0.1% in Triton X-100 to spread and wet the formulations to the plant. Inactivation of the virus under sunlight was decreased when added 800g of white carbon to 100 L of water in the white carbon formulation and 30% of molasses to the molasses's. In the formulation of white carbon and molasses mixtures, activation of the virus was increased when mixtured 500g of the former with 10% of the latter. Three formulations were persisted their pathogenicity more than 95% of mortality at 3 days p.i. Encapsulation of the polyhedral surface was more distinctively coated with the carbon and showed more effective in the residual effects of the white carbon than others, but the molasses more attractive for larval feeding.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.745-754
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• 2013

This study evaluated the optimal soil washing conditions for toxic metals considering the removal efficiency of toxic metals from contaminated soils as well as from soil washing effluents. In the contaminated soils, As was the major contaminant and extracted by sodium hydroxide solution better than by sulfuric acid. However, in the case of the treatment of soil washing effluents, sodium hydroxide was less effective extractant because soil organic matter extracted by sodium hydroxide prevented the solid-liquid phase separation and toxic metal removal. In the treatment of soil washing effluents with sulfuric acid, toxic metals in the effluents were mostly precipitated at the pH above 6.5. In addition, granular ferric oxide (GFO) as an adsorbent enhanced the removal of As and Pb indicating that toxic metals in the washing effluents can be removed almost completely by the use of combined adsorption-neutralization process. This study suggests that soil washing techniques for toxic metals should be optimized based on the physical and chemical properties of the contaminated soils, the nature of chemical extractant, and the removal efficiency and effectiveness of toxic metals from the soils as well as soil washing effluents.

• Analytical Science and Technology
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• v.13 no.2
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• pp.208-214
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• 2000

The formation and dissolution of hydroxides, carbonates and hydroxyapatite (HAp), which depend on the pH of solution, are important factor for the preparation of homogeneous and fine HAp, $Ca_{10-x}(HPO_4)_x(PO_4)_{6-x}(OH)_{2-x}(x=0)$, ceramic powder from the $Ca-PO_4-H_2O$ system. Since the solubility of each complex ion is a linear function of pH, the solubility diagram can be obtained by plotting the logarithmic molar concentrations calculated from the values of the equilibrium constants and solubility products for hydroxides, carbonates, and hydroxyapatite. The optimum pH condition for the formation of single phase $Ca_{10-x}(HPO_4)_x(PO_4)_{6-x}(OH)_{2-x}(x=0)$ powder in $Ca-PO_4-H_2O$ system at $25^{\circ}C$ was estimated as $10.5{\pm}0.5$ through the theoretical consideration. The HAp powder dried at $80^{\circ}C$ showed a fine agglomerated particles with a size of 75 nm. The HAp powder calcined at $1,000^{\circ}C$ consisted of nearly homogeneous particles with a size of 450 nm. Even though the dried HAp particles consisted of agglomeration, mechanical properties were superior due to fine microstructure after sintering.

• Journal of the Mineralogical Society of Korea
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• v.5 no.1
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• pp.22-31
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• 1992

The Sancheong kaolin was fractionated into 9 size fractions by wet sieving, sedimentation, and centrifugation. The systematic X-ray diffraction combined with electron microscopy shows that the clay mineral composition of each size fraction is related to the original fabric of kaolin. Minerals such as halloysite (10${\AA}$), kaolinite, illite, and goethite which were formed by procipitation from solution are generally concentrated in the finer fractions, whereas verniculite which was formed by pseudomorphic transformation from other primary minerals are concentrated in the coarser factions. Kaolinits of various types which were formed by precipitation or transformation show a wide size range but they are generally concentrated in the coarser fractions. Halloysite or halloysite-kaolinite clusters in coarse fractions are the fragmentation products of the walls of original boxwork clusters in coarse fractions are the fragmentation products of the walls of original boxwork kaolin which escaped the complete dispersion even through the grinding, ultrasonic agitation, and chemical treatment. Separation of fully hydrated halloysite and kaolinite was possible by systematic wet size fractionation. The coarse-grained minerals such as vermiculite and kaolinite are usually removed during the preparation of clay fraction smaller than 2${\mu}m$, whereas the fine-grained minerals such as illite and goethite are overlooked in X-ray diffraction of the bulk samples because of their minor contents. The systematic wet size fractionation is needed for understanding of the exact mineralogy of kaolin of weathering origin.

• Korean Journal of Environmental Agriculture
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• v.17 no.1
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• pp.26-33
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• 1998

This experiment was conducted to classify the plant species occurring in the saline reclaimed land by saline tolerance. The vegetation of reclaimed land was composed of various plant species from halophyte to glycophyte showing different saline tolerances. In the investigated saline region, reclaimed land of Youngjong island, Inchun city, 175 species belonging to 32 families were found. Our survey was carried out in two region, having different salinity due to different desalinization. The electricalconductivity (EC) of more saline region showed 48.0mS/cm nd the other region showed 13.0mS/cm. It is assumed that intensity of precipitation and runoff of rainfall may cause salinity gradient in the investigated region. The plant species occurred in the experimental region were classified as 72 species of annual, 42 species of biennial, and 61 species of perennial according to life cycle. For knowing relationship between vegetation of saline region and saline tolerance of occurring species, we tested the saline susceptibility of plant species collected at the saline regions. Testing plants were cultured by nutrient solution containing 200 mM NaCl, the critical concentration of survival in glycophytes. The saline tolerance was graded by the growing capacity in the sand-culture system. The more saline-tolerant species screened by sand culture were Atriplex gmelini, Suaeda asparagoides, Aster tripolium, Suaeda maritima, Salicornia herbacea, and Suaeda japonica. The most saline tolerant family was Chenopodiaceae. Poaceae, Cyperaceae, and Brassicaceae showed relatively high tolerance to saline stress. In the course of growth under the high saline condition, the most noticeable change was the darkening of leaves by increasing of chlorophyll content. The chlorophyll contents were increased with saline stress in most species.

• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.575-579
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• 2006

Solid electrolyte interface is formed on a carbon electrode used as an anode in Li-ion battery, which can be of $Li^{+}$ intercalation/deintercalation during the first cycle. The passivation film formed by a solvent decomposition during the initial charge process affects cell performance and it was one of the main reason of an initial irreversible capacity. This paper describes the use, for the first time, of $Li_2CO_3$ as the additive for the formation of a passivation film on the carbon surface to suppress the initial irreversible reaction. Chronopotentiometry, cyclic voltammetry, and impedance spectroscopy were used to investigate the effects of the $Li_{2}CO_{3}$ additive. Scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction were also used to monitor changes in the surface morphology and composition of the passivation film formed by solvent decomposition and the precipitation of $Li_{2}CO_{3}$. The addition of $Li_{2}CO_{3}$ to a solution of 1 M $LiPF_{6}$/EC:MA (1:3, v/v) resulted in a decrease in the initial irreversible capacity and it was due to the suppression of the solvent decomposition on the electrode surface.

• Journal of Hydrogen and New Energy
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• v.22 no.6
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• pp.749-758
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• 2011

The present work explores the performance and operation limit of electrodialysis cell for HI concentration in sulfur iodine thermochemical hydrogen production process, For this purpose, the electrodialysis cell was assembled with Nafion 117 as a PEM membrane and two activated carbon papers as the electrodes. HIx solution was prepared with composition of HI: $I_2$: $H_2O$ = 1: 0.5~2.5: 5.2 in molar ratio. The cell and its peripheral apparatus were placed in the specially designed convective oven in order to uniformly maintain the operation temperature. As operation temperature increased, the amount of water transport from anode to cathode increased, thus reducing HI molarity in catholyte. Meanwhile, the current efficiency was constant as about 90 %, irrespective of temperature change. The cell voltage increased with initial $I_2$ mole ratio as well as anolyte to catholyte mole ratio. Moreover the cell voltage overshot took place within 10 h cell operation, which is due to the $I_2$ precipitation inside the cell. From the analysis of $I_2$ mole ratio in the anolyte, it is noted that operation limit (in $I_2$ mole ratio) of the electrodialysis cell, arising from was measured to be 3.2, which is much lower than bulk solubility limit of 4.7.

• Journal of the Mineralogical Society of Korea
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• v.32 no.2
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• pp.79-86
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• 2019

The white aluminum phases in acid mine drainage usually precipitates when mixed with stream waters with relatively high pH. The minerals in white precipitates play important roles in controlling the behavior of heavy metals by adsorbing and coprecipitation. By the phase transition of these minerals in white precipitates, dissolution and readsorption of heavy metals may occur. This study was conducted to obtain preliminary information on the phase transition of the mineral phases in white precipitates. In this study, the mineral phase changes in the white precipitates collected from the stream around Dogye Mining Site over time were investigated with different pH values and temperatures. White precipitates consist mainly of basaluminite, amorphous $Al(OH)_3$ and a small amount of $Al_{13}$-tridecamer. During aging, the incongruent dissolution of the basaluminite occurs first, increasing the content of the amorphous $Al(OH)_3$. After that, pseudoboehmite is finally precipitated following the precursor phase of pseudoboehmite. At $80^{\circ}C$, this series of processes was clearly observed, but at relatively low temperatures, no noticeable changes were observed from the initial condition with coexisting basaluminite and amorphous $Al(OH)_3$. At high pH, the desorption of $SO{_4}^{2-}$ group in basaluminite was initiated to promote phase transition to the pseudoboehmite precursor. Over time, the solution pH decreases due to the dissolution and phase transition of the minerals, and even after the precipitation of pseudoboehmite, only the particle size slightly increased but no clear cystal form was observed.