• Journal of the Mineralogical Society of Korea
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• v.25 no.2
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• pp.85-94
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• 2012

The $AsO_4$ ion in acid mine drainage has been known to substitute for $SO_4$ in schwertmannite and prevent schwertmannite from being converted to goethite. There have been studies on the heavy metal sorption on schwertmannite, but no experimental results have been reported on the characteristics of heavy metal sorption on $AsO_4$-substituted schwertmannite. In this study, we conducted sorption experiments of Cu, Pb, and Zn on the $AsO_4$-substituted schwertmannite at pH 4 and 6 in the solution of 3, 10, 30, and 100 mg/L concentrations. For all heavy metals, the sorbed heavy metals significantly increase at pH 6 compared with at pH 4. At both pH 4 and 6, Pb shows the highest sorption capacity and those of Cu and Zn are similar. With increasing time, the sorbed heavy meal contents increase too. However, in the case of Zn, the most sorptions occur at the initial stage and no significant increase is observed with time. Among the concentration ranges in which we conducted the experiment, the increasing trend is clear in high concentrated solutions such as 100 mg/L. We applied several sorption kinetic model and it shows that the diffusion process may be the most important factor controlling the sorption kinetics of Cu, Pb, and Zn on $AsO_4$-substituted schwertmannite. Considering the previous results that pure schwertmannite has similar sorption capacity for all three heavy metals at pH 6 and has higher sorption capacity for Cu and Pb than Zn at pH 4, our experiments indicates that substitution of $AsO_4$ for $SO_4$ on schwertmannite changes surface and sorption characteristics of schwertmannite. It also shows that $AsO_4$ contributes not only to the stability of schwertmannite, but also to the mobility of heavy metals in acid mine drainage.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.2
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• pp.3018-3030
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• 1973

This study was carried out to investigate the effects of various mix designs of concrete on the compressive strengths and corrosive rates when the concretes were immersed in sea water of the West Sea, as the part of study related to durated to durability of concrete by action of the sea water. Concrete mix designs used in this study were ordinary Concrete mix, Concrete mixes with different admixtures such as fly ash, pozzolith and vinsol resin, and pozzolan concrete mix. The concrete specimens were made and cured for 7 days and 28 days in the fresh water in accordance with the Korean Standard specification for concrete. Compressive strengths of the specimens were measured after immersing the specimens for one year in fresh water and sea water which were placed indoors. The sea water used in this test was taken from the Bay of Ahsan. Corrosive rate was also tested after immersing the specimens in the same sea water and placed indoors for one year. The results obtained from the tests are summarized as follows; 1. Compressive strength of an ordinary concrete was the lowest of the various mix desings of concrete immersed both in the fresh water and the sea water. Therefore, the uses of pozzolan cement, fly ash, pozoolith and vinsol resin in mix design of concrete had and effect on increasing compressive strength. 2. Pozzolan concrete was the most effective on compressive strength in the fresh water, but it had less effect than concrete with fly ash admixture immersed in the sea water. 3. The use of fly ash admixture in mix design of concrete showed higher strength as the immersing age is longer both in fresh water and sea water than the other concretes besides pozzolan concrete, but the concretewith fly ash admixture had lower strength than pozzolan concrete in the sea water. Therefore, concrete with fly ash admixture might be better than the pozzolan concrete as far as durability of concrete to sea water was concerned. 4. The use of pozzolith admixture in mix design of concrete had less compressive strength than the use of pozzolan cement for fly ash admixture both in fresh water and sea water. However, the concrete with pozzolith admixture was much stronger than one with vinsol resin admixture in fresh water, but somewhat stronger in the sea water. 5. Though the use of vinsol resin admixture was more effective than ordinary concrete on compressive strength both in fresh water and sea water, it was the least compressive strength among the other concretes. 6. Relation between compressive strengths and absorption rates of every kind of concrete besides concrete with fly ash admixture showed a linear regression line and the compressive strength is highee as the absorption rate is lower. Concrete with fly ash admixture had extremely high strength in comparison with corresponding adsorption rates of the other concretes. 7. Corrosive appearance on the surface of concretes was not occured significantly when exposed to the sea water for one year, However, the specimens of concretes besides ordinary concrete were a little heavier than those cured in fresh water for 28 days.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.19-26
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• 2023

Hydrogen, a clean energy source free of COx emissions, is poised to replace fossil fuels, with its usage on the rise. Despite its high energy content per unit mass, hydrogen faces limitations in storage and transportation due to its low storage density and challenges in long-term storage. In contrast, ammonia offers a high storage capacity per unit volume and is relatively easy to liquefy, making it an attractive option for storing and transporting large volumes of hydrogen. While NH₃ decomposition is an endothermic reaction, achieving excellent low-temperature catalytic activity is essential for process efficiency and cost-effectiveness. The study examined the effects of different zeolite types (5A, NaY, ZSM5) on NH₃ decomposition activity, considering differences in pore structure, cations, and Si/Al-ratio. Notably, the 5A zeolite facilitated the high dispersion of Ni across the surface, inside pores, and within the structure. Its low Si/Al ratio contributed to abundant acidity, enhancing ammonia adsorption. Additionally, the presence of Na and Ca cations in the support created medium basic sites that improved N₂ desorption rates. As a result, among the prepared catalysts, the 15 wt%Ni/5A catalyst exhibited the highest NH₃ conversion and a high H₂ formation rate of 23.5 mmol/g_cat·min (30,000 mL/g_cat·h, 600 ℃). This performance was attributed to the strong metal-support interaction and the enhancement of N₂ desorption rates through the presence of medium basic sites.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.899-909
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• 2023

In this study, the material scientific characteristics of Hobun pigments used as white inorganic pigment for traditional cultural heritage were identified according to the type of shell and calcination and evaluated the stability of the preservation environment. For the purpose of this, we collected 2 different types of Hobun pigments made by oyster and clam shell and its calcined products(at 1,150℃). Hobun pigments before calcined identified calcium carbonate such as calcite, aragonite but calcination derived changing main composition to portlandite and calcite. Results of FE-SEM showed characteristics microstructure for each shell but pigments after calcined observed porous structure. Porous granule highly caused oil adsorption according to increase specific surface area of pigments. In addition, the whiteness improved after calcined pigments compared to non-calcined pigments, and the color improvement rate of Hobun pigment (CS) which made of clam shell was higher. As a result of the accelerated weathering test, the Hobun pigment-colored specimen had a color difference value of less than 2 after the test, which was difficult to recognize with the naked eye. In particular, the color stability has improved as the color difference value of the Hobun pigment is smaller after calcined compared to before non-calcined pigment. However, it was confirmed that the stability of the painting layer was lower in the specimen after calcined pigment. For antifungal activity test, Aspergillus niger, Tyromyces palustris and Trametes versicolor were used as test fungi, and all pigments were found to have preventive and protective effects against fungi. Especially, the antifungal effect of the calcined pigment was excellent, which is due to the stronger basicity of the pigment.