• Journal of the Korea Concrete Institute
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• v.29 no.4
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• pp.415-424
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• 2017

The purpose of this study is to investigate the effect of sulfate (${SO_4}^{2-}$) and magnesium ($Mg^{2+}$) ions on sulfate resistance of Alkali-activated materials using Fly ash and Ground granulated blast furnace slag (GGBFS). In this research, 30%, 50% and 100% of GGBFS was replaced by sodium silicate modules ($Ms(SiO_2/Na_2O)$, molar ratio, 1.0, 1.5 and 2.0). In order to investigate the effects of $Mg^{2+}$ and ${SO_4}^{2-}$, compression strength, weight change, lengh expansion of the samples were measured in 10% sodium sulfate ($Na_2SO_4$), 10%, 5% and 2.5% magnesium sulfate ($MgSO_4$), 10% magnesium nitrate ($Mg(NO_3)_2$), 10% [magnesium chloride ($MgCl_2$) + sodium sulfate ($Na_2SO_4$)] and 10% [magnesium nitrate $(Mg(NO_3)_2$ + sodium sulfate ($Na_2SO_4$)] solution, respectively and X-ray diffraction analysis was conducted after each experiment. As a result, when $Mg^{2+}$ and ${SO_4}^{2-}$ coexist, degradation of compressive strength and expansion of the sample were caused by sulfate erosion. It was found that the reaction of $Mg^{2+}$ with Calcium Silicate Hydrate (C-S-H) occurred and $Ca^{2+}$ was produced. Then the Gypsum ($CaSO_4{\cdot}2H_2O$) was formed due to reaction between $Ca^{2+}$ and ${SO_4}^{2-}$, and also Magnesium hydroxide ($Mg(OH)_2$, Brucite) was produced by the reaction between $Mg^{2+}$ and $OH^-$.

• Journal of Korean Society of Forest Science
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• v.109 no.2
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• pp.157-168
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• 2020

The sensitivity of forest soil to acidification in the Republic of Korea (ROK) was evaluated based on pH_H2O, cation exchange capacity (CEC), and base saturation (BS). Sensitivity to acidification was categorized into three grades: adequate level (AL, pH ≧ 4.2, CEC ≧ 15cmol/kg, BS ≧ 15%), caution level (CL, at least one indicator is below AL), and severe Level (SL, all three indicators are below AL). Soil samples were collected from the 65 stationary monitoring plots (40 × 40 ㎢), distributed throughout ROK. Only 19% of soil samples were classified as AL, while 66% and 15% were CL and SL, respectively. The median of pH_H2O, CEC, BS, and Ca/Al indicator in AL soils was pH 4.64, 20.7cmol/kg, 29%, and 6.3, respectively. Moreover, BC_ex (K⁺, Mg²⁺, Ca²⁺) and available phosphorus (AP) concentration compared with a threshold value and molar ratio of BC_ex and AP to total nitrogen (TN) was high. This indicates that AL soils have a good nutrient condition. The molar Ca/Al ratio, an indicator for toxicity of exchangeable aluminum (Al_ex), was more than 1, indicating no negative impact of Al_ex on plant growth. On the contrary, the median of pH_H2O, CEC, and BS in SL soils was pH 4.02, 13.2cmol/kg, and 10%, respectively. The Ca/Al index was less than 0.6, which indicates that negative impacts of Al_ex on plants were high. Furthermore, both the concentration of BC_ex in SL soils and the BC_ex/TN ratio were the lowest among the three acidity degrees. This shows that SLsoils can be degraded by soil acidification compared with less acidic soils.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.97-105
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• 2005

[ $11\AA$ ] tobermorite$(5CaO{\cdot}6SiO_2{\cdot}5H_2O)$ is synthesized from the mixtures of calcium hydroride and quartz using alumina in a molar ratio $Ca(OH)_2/SiO_2$ of 0.8 at $180^{\circ}C$ for 8 and 24 hrs under saturated steam pressure. The influence of alumina on the formation of $11\AA$ tobermorite was investigated by X-ray diffraction, differential thermal analysis and infrared spectroscopy. $11\AA$ tobermorite containing increasingly larger amounts of aluminum showed a shift of the basal spacing from 11.3 to $11.6\AA$. In general, there was a direct linear relation between the basal spacing and added content of alumina. The differential thermal analysis curves showed that $11\AA$ tobermorite with increasing alumina contents exhibited the exothermic peak at high temperature, namely $11\AA$ tobermorite containing aluminum gave a sharp exothermic peak at temperature around $850\~860^{\circ}C$ in the case of $S_3\~S_5$. The absorption band at $1607\~1620cm^{-1}$ is attributed to the bending vibration of water, and the position of the main O-H stretching and Si-O lattice vibration of $11\AA$ tobermorite at 3500 and $965cm^{-1}$ respectively is not altered. Consequently the existence of alumina accelerates the crystallization of $11\AA$ tobermorite, and that the aluminum ion appears to substitute for the silicon ion in $11\AA$ tobermorite structure. Al-containing tobermorite is distinguished from Al-free tobermorite.

• Journal of the Korean Chemical Society
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• v.31 no.4
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• pp.315-321
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• 1987

The ligand, 2,10-dibenzyl-4,6,8-trioxo-3,9-diaza undecane dioic acid(DTDA) for the extraction of uranium was synthesized under dry nitrogen from phenylalanine and 3-oxoglutaric acid. Extraction was performed by stirring a solution of DTDA in dichloromethane for 1 hour with an aqueous solution of $UO_2(ClO_4)_2{\cdot}6H_2O$ at various pH values and at different $DTDA/UO_2{^{2+}}$ molar ratios. Extraction efficiency reaches a maximum when the pH of the aqueous phase was ca 8.0. The extraction percentage was affected by concentration of DTDA and increases with the $DTDA/UO_2{^{2+}}$ molar ratio to complete extraction with a 4 fold excess of DTDA. The high selectivity of the DTDA for uranium was ascertained by competition experiments with other cations. The bound uranyl ion was quantitatively liberated within few minutes from the organic phase by treatment with an aqueous 1M HCI solution and DTDA was recovered very satisfactorily from the organic phase. The values of the over-all formation constants of the complex between uranyl ion and DTDA were determined to be the following : ${\beta}_1=1.20{\times}10^5\;,\;{\beta}_2=1.01{\times}10^8$.

• Journal of Environmental Science International
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• v.10 no.6
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• pp.387-391
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• 2001

The hydroxyapatite(HAp) as a carrier the for ion exchange agent of $Ag^+$ions was prepared in semiconductor fabrication, The Ca/P molar ratio of the HAp was 1.65. The HAp is molded in shape of the antimcrobial ball and then sintered at 100$0^{\circ}C$ Ag-containing HAp(HAp-Ag) was prepared by incorporating $Ag^+$/ions in HAp crystals through an ion-exchange reaction in solutions containing 0.01M $AgNO_3$. The antimicrobial effect of HAp-Ag for bacteria such as Escherichial coli and Staphylococcus aureus has been Investigated. The concentrations of silver in the antimicrobial ball was determined by inductively coupled plasma and the amount of $Ag^+$ions was 9.0$\mu\textrm{g}$/g. The HAp-Ag exhibited excellent antimicrobial effect for bacteria such as E. coli and S. aureus. The bactericidal activity was considered to be caused by direct contact of bacteria with $Ag^+$ions in the HAp crystals. The HAp would likely to be possible as a carrier of antimicrobial metal ions such as Ag, Cu, and Zn by recycling of waste sludge in the semiconductor fabrication process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.5
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• pp.243-248
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• 2010

Si-substituted biphasic calcium phosphates (Si-BCP) were prepared by co-precipitation method. X-ray diffraction and fourier transform infrared spectroscopy were used to characterize the structure of Si-BCP powders. The Si-BCP powders with various Ca/(P+Si) molar ratio were carried out on structural change of hydroxyapatite (HAp) and ${\beta}$-tricalcium phosphate ($\ss$-TCP). The in-vitro bioactivity of the Si-BCP powders was determined by immersing the powders in SBF solution, after that observing the chemical composition and morphology change by X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy.

• The Korean Journal of Pharmacology
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• v.24 no.1
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• pp.111-123
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• 1988

Neutrophil elastases were purified by a three step procedure consiting of one Sephadex G-75 and two HPLC elutions. The elastases cross-reacted with antibodies to human neutrophil elastase. Three bands with molecular weights between 26,000 and 29,700 were observed by gel electrophoresis. At each stage of purification the quantity of Zn increased, reaching molar ratio of 2:1 with elastase in the most purified samples. Calcium content. was seletively elevated during the earlier stages of purification but decreased to a ratio of 0.25 to 1 with elastase at the final step of purfication. Neutrophil elastase could be inhibited by EDTA, EGTA and 1,10-phenanthroline. EGTA inhbition was noncompetitive inhibition and reversible only if the time of preincubation was relatively short, indicating the instability of the apoenzyme. The concentration of chelator required to show significant inhibition of elastase was also dependent upon the stage of purity and the ionic strength of the reaction mixture. Inhibition by EGTA, followed by the removal of EGTA, could be reversed by Zn. In the presence of EGTA the enzyme could be returened to full activity by the addition of Zn, Mn and Ca, but not Mg or Na. All of the above evidence strongly supports human neturophil elastase could be a metalloenzyme as well as a serine protease.

• Journal of the Korean Chemical Society
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• v.46 no.6
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• pp.515-522
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• 2002

Solid beta-dicalcium silicate hydrate $(\beta-C_2SH)$ synthesized under hydrothermal conditions at $240^{\circ}C$ and Ca/Si=2 molar ratio shows cation exchange properties towards divalent metal cations such as Fe, Cu, Zn, Cd, or Pb. The ability of metal cation uptake by the solid was found to be in the order: $Fe^{2+}$〉$Cu^{2+}$〉$Zn^{2+}$〉$Cd^{2+}$ = $Pb^{2+}$. Cesium selectivity of the solid was demonstrated in the presence of univalent cation such as $Li^+$, $Na^+$ and $K^+$ and divalent cations such as $Ca^{2+}$, $Mg^{2+}$ and $Ba^{2+}$, which are one hundred times more concentrated than the $Cs^+$. The uptake of $Cs^+$ is maximum in the presence of $Mg^{2+}$ whereas it is minimum in the presence of $K^+$. The different affinities of ${\beta}-C_2SH$ towards divalent metal cations can be used for the separation of those ions. Due to its selectivity for cesium it can be used in partitioning of radioactive Cs+ from nuclear wastes containing numerous cations. The mechanism of the metal cation exchange and cesium selectivity reactions by the solid is studied.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.580-586
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• 2009

In this study, co-combustion characteristics of Chinese bituminous coal and North Korean anthracite were investigated using a 2 MWe scale circulating fluidized bed power plant. At first, the combustion efficiency of bituminous coal of China and Australia as a function of excess air ratio and temperature were observed. The results showed that the combustion efficiency was influenced by particle size and volatile content of coal, the combustion efficiency of Chinese bituminous coal was over 99.5%. The unburned carbon particles from fly ash and bottom ash were a content 5~7% and 0.3%, respectively. The combustion efficiency with the mixture ratio 20% of bituminous coal and anthracite decreased over 5% because of the increase of entrained particles by a small average particle size of anthracite in the combustor. However, the outlet concentration of $SO_2$ and $NO_x$ was not changed remarkably. The concentrations of the typical air pollutants such as $NO_x$ and $SO_2$ were 200~250 ppm($O_2$ 6%), 100~320 ppm($O_2$ 6%) respectively. The outlet concentration of $NO_x$ was decreased to 30~65% with $NH_3$ supplying rate of 2~13 l/min in SCR process. The $SO_x$ removal efficiency was up to 70% by in-furnace desulfurization using limestone with Ca/S molar of approximately 6.5. With wet scrubbing using $Mg(OH)_2$ as absorbent, the $SO_x$ removal efficiency reached 100% under near pH 5.0 of scrubbing liquid.

• Journal of the Korean earth science society
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• v.38 no.7
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• pp.570-580
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• 2017

The purpose of the study was to evaluate the groundwater quality of Sinan-gun, Jeollanam-do, an island located in the southern part of the Korean peninsula where the effect of seawater on the groundwater quality had not been investigated in the past. In order to evaluate its effect, the hydrogeological parameters including groundwater quality and major dissolved components were investigated. The water quality was measured four times in the field, and 74 of 163 samples that showed the high conductivity value of more than $500{\mu}S/cm$ and the influence of seawater on the groundwater were analyzed by $Cl^-/HCO_3{^-}$ molar ratio. The results showed that, 40 samples out of 74 were found to have a value of 2.8 or more, indicating severe and very severe effects. According to the type of groundwater quality, the ratio of samples belonging to Na-Cl type, which is considered to be influenced by the direct seawater, is 35.3% for bedrock groundwater and 52.5% for weathered zone and alluvial groundwater. In the evolution stage of groundwater due to seawater infiltration, the type of Ca-Cl prior to the Na-Cl type is 44.1% in bedrock groundwater and 45% in weathered zone and alluvial groundwater. The effect of sea water on the aquifer is likely to be influenced by distance from the shore, pumped water, and tide.