• Journal of the Korean earth science society
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• v.26 no.3
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• pp.305-312
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• 2005

Degrees of serpentinization from the original rocks of Choongnam serpentinites such as dunite and harzburgite are well matched with O'Hanley's textural stages of serpentinites (1996). Colors of chromian spinels in serpentinites are brown and/or red in dunites, and red in harzburgite. Also, colors of chromian spinels changed darker from brown and/or red according to the degree of serpentinization and more darker by steatitization because of increasing Fe ions.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.4
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• pp.235-239
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• 2001

급속 표면가열과 기존의 전기로 열처리에서 얻어지는 경화의 가장 중요한 차이점은 전자가 불균질한 오스테나이트를 생성할 수도 있다는 것이다. 즉, 오스테나이트에 미용해 탄화물이 존재할 수도 있고 탄소와 합금원소의 농도 구배가 존재할 수도 있다. 합금강에서, 이러한 탄화물은 합금성분이 비교적 높기 때문에 철 탄화물에 비해서는 좀 더 천천히 기지에 용해된다. 또한 망간, 크롬, 니켈 및 몰리브덴과 같은 치환형 합금원소는 천천히 확산한다. 따라서, 균일한 오스테나이트를 생성하기 위해서는 더 많은 시간과 더 높은 온도가 요구된다. 그러나 표면 구역의 낮은 경화능에도 불구하고 냉각속도가 마르텐사이트의 체적분율이 큰 미세조직을 확보할 만큼 충분히 크기 때문에 경도는 높게 된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6B
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• pp.677-682
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• 2006

Dodecyldimethylethylammonium (DDDEA), a cationic surfactant, and aluminum metal ions were used with bentonite to synthesize to synthesize an improved organo bentonite. Among three different synthesis procedure for organo bentonites, aluminium-pillared bentonite showed the highest DDDEA sorption, which indicated that aluminium-pillared organo bentonite would exhibit the highest sorption capacity for organic contaminants. Aluminium pillared organo bentonite also showed a high sorption capability for phosphorus, while it did not exhibit strong sorption for nitrate. In the meantime, more desorption was observed with aluminium-pillared organo bentonite than ordinary organo bentonites.

• Journal of the Mineralogical Society of Korea
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• v.21 no.3
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• pp.247-259
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• 2008

$TiO_2$ coatings on kaolinite powders by sol-gel method were carried out using mixture of titanium isopropoxide, ethanol as solvent, HCl as a catalyst and $H_{2}O$ for hydrolysis. The mole ratio of reaction mixture, stirring time. aging time, crystallization time and crystallization temperature influenced to the crystallization of $TiO_2$ coated on kaolinite and metakaolinite Powders. Optimum condition for $TiO_2$ coatings on kaolinite was as follows; TIP 0.1 mol, $H_{2}O$ 0.15 mol, HCl 0.005 mol, ethanol 100 ml, raw kaolinite 50 g, stirring time 4 hrs, aging time 24 hrs, crystallization time 2 hrs and crystallization temperature $1050^{\circ}C$. The crystallinity of the anatase under optimum condition was about 17.61%. The anatase crystallinity of the $TiO_2$ coated on raw kaolinitc powders (17.61% at $1050^{\circ}C$) was higher at the lower calcination temperature compared with metakaolinite (17.39% at $1200^{\circ}C$).

• Journal of Soil and Groundwater Environment
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• v.6 no.3
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• pp.21-29
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• 2001

Organobentonite modified with hexadecyltrimethylammonium (HDTMA) was used to quantify adsorption of heavy metals. Adsorption of cadmium and lead increased with increasing pH and soil/solution ratio. Based on these experiments, an optimal soil/solution ratio and an optimal pH was selected. Adsorption experiments with cadmium and lead were conducted to quantify adsorption selectivity on bentonite and organobentonite. Adsorption of heavy metals on organobentonite was slightly reduced relative to bentonite. Because of competition between cadmium and lead, adsorption of each metal was reduced due to the presence of the other. Adsorption selectivity of cadmium was higher than lead. This study used the principle of hard soft-acid-base (HSAB) to interpret adsorption.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.3
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• pp.368-373
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• 2017

Comparative fining trials were conducted in a laboratory to study the effects of fining treatments including polyvinylpolypyrrolidone (PVPP) and bentonite on the color and clearness of apple wine. The wines were subjected to three different fining treatments: PVPP, PVPP+bentonite (applied at the same time), and PVPP+bentonite (24 h later). Based on the results, all treatments induced noticeable decreases in wine color (APHA value) and turbidity. The treatment including PVPP and bentonite at the same time provided the best results in relation to wine color and clearness. PVPP was the most effective in the reduction of phenolic compounds, which means it helped wine obtain a paler color. Organic acids and aromatic profile were not altered by the fining treatments.

• Tunnel and Underground Space
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• v.30 no.3
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• pp.193-213
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• 2020

A mathematical model to simulate more realistically the penetration of compacted bentonite buffer installed in the deposition hole into the discontinuity in the excavation damaged zone formed at the inner wall of the deposition hole in the geological repository for spent fuel is developed. In this model, the penetration of compacted bentonite is assumed to be the flow of Bingham fluid through the parallel planar rock fracture. The penetration of compacted bentonite is analyzed using the developed model. The results show that the maximum penetration depth of compacted bentonite into the rock fracture is proportioned to the swelling pressure of saturated compacted bentonite and the aperture of rock fracture. However, it is in inverse proportion to the yield strength of compacted bentonite. The viscosity of compacted bentonite dominates the penetration rate of compacted bentonite, but has no influence to the maximum penetration depth.

• Economic and Environmental Geology
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• v.57 no.3
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• pp.319-327
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• 2024

Calcite and aragonite are polymorphs with the chemical formula CaCO₃. In this study, natural limestone and aragonite, as well as scallop and clam shells composed of calcite and aragonite, were used as the pH-raising neutralizing agents for model solutions containing various heavy metals such as Cd, Cu, Fe, Mn, and Zn to simulate acidic drainage. According to the experimental results, pH-raising effect is higher in the shell materials compared to natural ores for both the calcite and aragonite types. Natural calcite and scallop shells are found to be the most suitable media for Cd removal, while over 95% efficiency for Cu and Fe removal was observed in all four media. Zn removal efficiency is higher in aragonite and clam shells, while Mn removal efficiency is relatively low, to be below 50%, for all four media. Overall, the heavy metal removal efficiency, except for Mn, was over 90%, in the order of Fe > Cu > Cd > Zn > Mn.

• Journal of the Korean earth science society
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• v.26 no.3
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• pp.297-304
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• 2005

Serpentinites in Chungnam area are mainly composed of serpentines. Serpentines of olivine origin consist of pseudomorphs of olivines and show mesh textureen closed with magnetites along the boundaries of serpentine crystals. In some serpentinites, serpentinization is occurred in crystal boundaries and/or cracks of olivines and pyroxenes which are relict minerals of dunite and harzburgite. On the process from olivine to serpentine, Mg ions are greatly decreased and Si ions are greatly increased, and $Fe^{2+}\;and\;Fe^{3+}$ ions are a little decreased. But, on the process from pyroxene to serpentine, Si ions are greatly decreased and Mg ions are greatly increased. Magnetites around the serpentine crystals were formed from the iron which had been left out through this serpentinization process of olivine. Serpentinization from the original rocks such as dunite and harzburgite in Chungnam area was occurred by various waters affected after formation of original rock, and particularly by metamorphic water in the metamorphic conditions ranging from green schist facies to granulite facies through amphibolite facies.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.2
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• pp.133-146
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• 2021

Aragonite is one of common polymorphs of calcium carbonate (CaCO₃) and formed via biological or physical processes through precipitation in many different environments including marine ecosystems. It is noted that aragonite formation and growth as well as the substitution of trace elements such as strontium (Sr) in the aragonite structure would be dependant on several key parameters such as concentrations of chemical species and temperature. In this study, properties of the incorporation of Sr into aragonite were investigated over a wide range of various saturation conditions and temperatures similar to the marine ecosystem. All pure aragonite samples were inorganically synthesized through a constant-addition method with varying concentrations of the reactive species ([Ca]=[CO₃] 0.01-1 M), injection rates of the reaction solution (0.085-17 mL/min), and solution temperatures (5-40 ℃). Pure aragonite was also formed even under the Sr incorporation conditions (0.02-0.5 M, 15-40 ℃). When temperature and saturation index (SI) with respect to aragonite increased, the crystallinity and the crystal size of aragonite increased indicating the growth of aragonite crystal. However, it was difficult to interpret the crystal growth rate because the crystal growth rate calculated using BET-specific surface area was significantly influenced by the crystal morphology. The distribution coefficient of Sr (K_Sr) into aragonite decreased from 2.37 to 1.57 with increasing concentrations of species (Ca²⁺ and CO₃^2-) at a range of 0.02-0.5 M. Similarly, it was also found that K_Sr decreased 1.90 to 1.54 at a range of 15-40 ℃. All K_Sr values are greater than 1, and the inverse correlation between the K_Sr and the crystal growth rate indicate that Sr incorporation into aragonite is in a compatible relationship.