• Journal of the Mineralogical Society of Korea
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• v.31 no.2
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• pp.67-73
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• 2018

The objective of this study was to investigate the application of sulfate solvents for the economic and eco-friendly leaching of valuable metals from Au concentrate using an acid bake-water leaching system (AWS). AWS experiments were performed using an electric furnace with various baking temperatures ($100-500^{\circ}C$) and sulfate solvents ($H_2SO_4$, $K_2SO_4$, $(NH_4)_2SO_4$, $MgSO_4$, and $CaSO_4$). The efficiency of the valuable metal leaching increased as the baking temperature was increased to $400^{\circ}C$. Based on the AWS leaching time experiments, the maximum leaching rate occurred with the aqueous $(NH_4)_2SO_4$ solvent. This study demonstrates that aqueous $(NH_4)_2SO_4$ could be used as an effective solvent for valuable metal leaching using an AWS.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.275-277
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• 2005

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2006.04a
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• pp.215-216
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• 2006

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.421-424
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• 2008

The purpose of this experimental research is to investigate the influence of cement types on the resistance to acid and sulfate. For this purpose, concrete specimens with three types of cement such as ordinary portland cement(OPC), binary blended cement(BBC), and ternary blended cement(TBC) were made for water-binder(W/B) ratios of 32% and 43%, and then according to JSTM C 7401, the appearance change and ratio of mass change of them were estimated through the immersion tests by 5% sulfuric acid, 10% sodium sulfate, and 10% magnesium sulfate solution, respectively. It was observed from the test result that the resistance against acid and sulfate increased with decreasing W/B ratio and those of BBC and TBC concretes were better than the case of OPC concrete from immersion tests of 91 days.

• Journal of Wetlands Research
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• v.6 no.1
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• pp.117-132
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• 2004

Despite its significance in understanding ecological structure and biogeochemical element cycles, there have been few studies on the microbial mineralization of organic matter and mineralization pathway in the intertidal flat of Korea. We measured anaerobic mineralization of organic matter and sulfate reduction rate, and evaluated the significance of sulfate reduction in total anaerobic carbon respiration at the southern part of Ganghwa Island. Depth-integrated carbon mineralization rate down to 6 cm depth ranged from 41.9 to $89.4mmol\;m^{-2}d^{-1}$, which accounted for approximately 216 tons of organic matter mineralization in entire intertidal flat area of Ganghwa($300km^2$). The results indicated that capacity for the organic matter mineralization in the Ganghwa tidal flat is comparable to highly productive salt marsh environments. Mineralization rates in the sediment amended with acetate were 2~5 times higher than in unamended sediment. The results implied that microbial mineralization was limited by the availability of organic substrates, and the organic matter mineralization capacity seems to be higher than estimated at ambient organic substrate level. Depth-integrated sulfate reduction rates within 6 cm depth of the sediment ranged from 20.7 to $45.1mmol\;SO{_4}^{2-}m^{-2}d^{-1}$, and sulfate reduction was mostly responsible for organic matter remineralization. It should be noticed that the increase of $H_2S$ in the sulfate reduction dominated tidal flat may result in the decrease of biological diversity.

• Journal of the Society of Disaster Information
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• v.15 no.2
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• pp.239-248
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• 2019

Purpose: This study aims to enhance the resistance against sulfate attack compared to ordinary Portland cement (OPC) concrete by using liquid crystal display (LCD) as binder. Method: The fundamental properties including compressive strength and porosity of concrete replaced by LCD up to 15% at increments of 5% and in turn, the weight, volume, and strength loss of LCD-mixed concrete was analyzed. Results: For the concrete substituted by 5% of LCD, it showed the highest compressive strength at 28 days of curing, and particular at immersion of $Na_2SO_4$ solution, it was achieved the lowest loss of weight, volume and strength due to an decreased porosity at capillaries. In contrast, there is no distinct difference of the sulfate attack resistance between LCD-mixed concretes under exposure of $MgSO_4$ solution, excepted for OPC concrete. Conclusion: In this study, comparison of resistance to sulfate attack between LCD-mixed concretes, and it would be proposed the possibility of LCD usage as binder through long-term verification with extended replacement ratio and identification of changes of hydrates in the cement matrix.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.757-764
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• 2008

This paper was conducted to evaluate the durability of cement mortars exposed to varying concentrations of sodium sulfate for up to 540 days. Three types of cement mortars, namely OPC, SRC and SGC, were exposed to four sodium sulfate solutions with concentrations of 4225, 8450, 16900 and 33800 ppm of ${SO_4}^{2-}$ ions at ambient temperature. The sulfate deterioration was evaluated by measuring compressive strength and linear expansion of mortar specimens. Experimental results indicated that the maximum deterioration was noted in OPC mortar specimens in highly concentrated sulfate solution. In particular, the $C_3A$ content in cements plays a critical role in resisting expansion due to sodium sulfate attack. Additionally, the beneficial effect of GGBS was clearly observed showing a superior resistance against sodium sulfate attack, because of its lower permeability. Another important observation was that the parameters for the evaluation of deterioration degree are greatly dependent on the products formed by sulfate attack.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.335-336
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• 2000

도시 대기는 복잡한 성분을 가진 입자상 물질로 이루어져 있는데, 검댕 입자나 비산재(fly ash)등과 같이 일차오염물질과 복잡한 대기 화학반응에 의해 생성되는 이차오염물질이 혼재하고 있기 때문이다. 도시 대기 중의 입자상 물질은 대부분 황산염, 질산염, 암모늄염 입자상 물질과 유기 입자들로 구성되어 있는데, 탄소 입자는 도시의 미세 입자 중 거의 반 정도를 차지한다. (Ro et. el., 2000) 본 연구에서는 서울 대기에서의 입자상 물질에 대한 분석을 EPMA(Electron Probe X-ray Microanalysis)를 이용한 단일 입자 분석법(Single Particle Analysis)을 가지고 행하였다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.294-295
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• 2002

우리나라는 위도상 중위도 편서풍대에 위치하고 있어 황하유역과 중국 및 몽고사막 등에서 발생한 토양먼지가 매년 3-5월경에 편서풍을 타고 1,500-2,000km 이상의 거리를 이동하는 황사와 같은 대기오염 물질의 장거리 이동현상이 매년 발생하고 있다. 장거리 이동되는 황사의 성상은 발원지에서의 토양성분 이외에도 이동과정 중에서 오염된 지역의 가스상 물질들이 추가되고 가스와 입자의 상호작용에 의해 황산염이나 질산염 등이 많이 생성된다. (중략)

• Magazine of korean Tunnelling and Underground Space Association
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• v.3 no.1
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• pp.46-54
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• 2001