• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.103-110
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• 2011

This study is to comparatively analyze the characteristics of pH decrease in recycled fine aggregates for embankment and landfill produced from waste concrete by using natural process and artificial process. The result was as follows In case of recycled fine aggregates left outdoor, it was found that pH level was decreased if the thickness of embankment becomes thinner, or the materials left outdoors owing to high concentration of $CO_2$ in atmosphere caused by respirations of people. When the air was permeated, pH level was decreased more effectively. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$ in the recycled fine aggregates owing to high-pressure ventilators. In case of water spraying treatment, sprayed water facilitated hydration of unhydrated cement to dissolve calcium hydroxides which neutralized $CO_2$ in the atmosphere during desiccation process and decrease pH level by a considerable margin. In case of Immersed treatment, decrease of pH was not sufficient. When facilitating the supply of $CO_2$, pH level of the recycled fine aggregates was decreased by the largest margin. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$. From the above results, it was analyzed that the most effective method of reducing pH level of the recycled fine aggregates from the aspects of pH reduction performance, economic efficiency and workability was repeated wet-dry cycles of spraying water to the aggregates in the proportion of 1:0.5 by weight and then treating by forcefully blowing $CO_2$ gas into the aggregates.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.366-373
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• 2015

Construction waste is recycled and used for the efficient and eco-friendly disposal of construction waste increasing due to reconstruction and redevelopment project and so on. There is recycled aggregate as a typical case. And this recycled aggregate shows strong alkalinity due to calcium hydroxide, and causes many environmental problems. Therefore, this is a study on reduction in the strong alkalinity of recycled aggregate by using sodium phosphate based ammonium in order to reduce the pH of recycled aggregate. Besides, a possibility that a pH reducing agent of recycled aggregate could be applied to a site was evaluated. As a result, it was possible to verify that pH decreased as the percentage of pH reducing agent increased. It is thought that the pH reducing agent can be applied to a site by methods such as immersion and spray using the pH reducing agent in the process of producing recycled aggregates.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.182-185
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• 2005

울산광산 내 지표수와 토양 중의 공극수에 함유되어 있는 비소의 오염현황을 파악하고, pH와 산화-환원 전위 값의 변화에 따른 자연저감 능력을 평가하였다. 유비철석을 비롯한 비소함유 광물은 높은 산화-환원 전위 값과 낮은 pH 조건에서 해리되며, 이후 지하수의 진화과정에서 pH가 상승함에 따라 주로 5가의 비소형태로 존재하게 된다. 울산광산지역 지하수의 비소농도는 Eh가 높은 비포화대와 포화대 지하수의 경계부에서 높은 경향을 나타내며, 포화대의 상부에서는 Eh가 비교적 일정하나 비소 농도는 다양한 분포양상을 보인다. 포화대 하부에서 비소의 함량은 매우 낮으며, Eh 감소에 따라 비소 함량이 비례적으로 감소한다. 반응경로 과정에서 비소농도는 Eh<-0.1(V)인 지하수 포화대에서 가장 낮으며, pH가 상대적으로 낮고 산화-환원 전위값이 높은 비포화대에서 증가되는 경향을 보인다. 풍화 반응 정도가 높은 광미와 토양에서 비소농도 높으나, 용출실험에서 비소가 기준치 이하로 용출되는 것은 풍화반응과 토양에 의한 비소의 자연저감이 진행되고 있음을 반영한다. RMB를 이용한 중금속 제거능력 평가 실내실험에서, 산성과 알칼리 조건 모두에서 제거율이 높은 것으로 나타났다. 인회석과 철산화물질로 구성된 RMB는 친환경적이고 2차 오염문제를 극복할 수 있는 물질로서, 비소의 자연저감 능력을 향상시킬 수 있는 정화처리제로 활용이 가능할 것으로 판단된다.

• Journal of Radiation Protection and Research
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• v.14 no.2
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• pp.37-44
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• 1989

An improved water chemistry technique was studied to reduce radioactivity build-up in reactor coolant system. The technique is convering the current coordinated lithium-boron chemistry regime to the elevated lithium chemistry regime in order to maintain high pH. Correlations between reactor coolant pH and radioactivity build-up were analized by using pH data from domestic PWRs. Consequently, it was founded that high pH chemistry was moer effective for radioactivity build-up reduction than current chemistry regime. This fact had revealed that much portion of reactor coolant corrosion products were nickel ferrite rather than magnetite, and that pH value ranging 7.0-7.4 was appropriate for high-pH chemistry operation.

• Analytical Science and Technology
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• v.14 no.6
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• pp.516-521
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• 2001

This research was for reducing leachated concentration of hazardous pollutants in bottom ash from municipal solid waste combustors(200 tons/day) of Korea. Lead and copper compounds were selected as main pollutants. For reducing of leachated level, optimal conditions were observed using air oxidation for lead compounds and water washing method for copper compounds. and it was observed stable pH range of bottom ash from analyzing lechated level by pH variation.

• Clean Technology
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• v.19 no.1
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• pp.65-72
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• 2013

In this study, we investigated the activity of Pd and Cu co-incorporated on mesoporous silica support such as MCM-41 and SBA-15 for catalytic nitrate reduction in water. In pure hydrogen flow, nitrate concentration was gradually decreased with the reaction time, but nitrogen selectivity was too low due to very high pH of reaction medium after the reaction. In order to acquire high nitrogen selectivity, we utilized carbon dioxide as a pH buffer, which resulted in higher nitrogen selectivity (about 40%). For the above reaction conditions, Pd-Cu/MCM-41 showed better performance than Pd-Cu/SBA-15. The physicochemical properties of both catalysts were investigated to figure out the relationship between the characteristics of the catalysts and the catalytic activity on the catalytic nitrate reduction by $N_2$ adsoprtion-desorption, X-ray diffraction (XRD), $H_2$-temperature programmed reduction, X-ray photoelectron spectroscopy (XPS) techniques.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1129-1134
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• 2001

In the point of the Eco-concrete(Environmentally Friendly Concrete), it is very important to reduce the pH of high porous concrete by the pH to be able to grow plants, because the pH of concrete is l1~13. But the method of measuring the pH of high porous concrete is not well-defined, yet. Therefore, first, this paper report the method of measuring the pH of high porous concrete. Secondly this paper reports the pH reduction of high porous concrete to grow plants.

• Korean Journal of Food Science and Technology
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• v.44 no.3
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• pp.312-316
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• 2012

In order to understand the effect of hydrostatic pressure (HP) on Bacillus subtilis isolated from makgeolli, the survival of B. subtilis after HP treatment (400 MPa for 5 min) in various substrates including phosphate buffer, tryptone soya broth at pH 7 and 4, and makgeolli at pH 4 was evaluated depending on bacterial forms (spores and vegetative cells) and adaptation conditions ($25^{\circ}C$ for 3 h, or $10^{\circ}C$ for 24 h). Spores were generally resistant to HP (<1 log reduction) regardless of conditions. In contrast, vegetative cells were generally susceptible to HP (up to 3 log reduction-except makgeolli) and were more susceptible after 3 h at $25^{\circ}C$ compared to 24 h at $10^{\circ}C$. In vegetative cells inoculated makgeolli (7 log CFU/mL), the colonies were not detected after 24 h at $10^{\circ}C$. Consequently, B. subtilis in makgeolli easily existed as spores and the spores were resistant to HP. Results demonstrate that HP was more promising in the inactivation of vegetative cells.

• Economic and Environmental Geology
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• v.44 no.6
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• pp.485-492
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• 2011

Sorption of cyanide on granular activated carbon and attenuation of the cyanide by UV-light over a wide range of conditions such as pH and concentration were investigated through batch experiments. Cyanide uptake by activated carbon is much effective at $[CN]_{ini}$ < 2 mg/L. The sorption of cyanide on activated carbon at pH 7.0 is greater than that of pH 9.0. It is found that the ratio of CN uptake to CN in solution increases at pH 9.0 whereas at pH 7.0 the ratio decreases, suggesting that reactivity of activated carbon increases as a function of pH. The sorption of cyanide rapidly increases during the first 30 min, followed by sharp desorption until 3hr, and then the sorption increases and reaches the maximum sorption during the duration of experiments, implying that the sorption mode could be changed through conformational change during the initial stage of the cyanide uptake by activated carbon. Total amount of cyanide desorbed from the activated carbon during the period of desorption experiments is less than 1.5% of total sorbed cyanide, indicative of strong and stable sorption of cyanide on the activated carbon. The sorption with mixture of activated carbon and Ham-Baek sludge shows less effective on the removal of the cyanide. It is noted that UV-light is much effective on the removal of cyanide but also the attenuation is achieved until $[CN]_{tot}$ is up to 10 mg/L. Our findings demonstrate that both activated carbon and UV-light are very effective on the attenuation of cyanide over a wide range of environmental conditions.

• Journal of the Korean GEO-environmental Society
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• v.11 no.9
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• pp.39-45
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• 2010

Controlled low strength material(CLSM) is produced by mixing portland cement, fine aggregates, water and chemical admixtures. Sand is the most commonly used as the fine aggregates in the conventional CLSM. It is getting more and more difficult to obtain sand in Korea so it is required that the alternative materials be developed as the replacement of sand. Since the engineering characteristics of coal ash are similar to the sand, it becomes necessary to examine the application of the coal ash as the alternative material for CLSM and as the environment-friendly material. When the results meet the optimum pH level that plants can live, it can be expanded the scale of application of the study on the plant as the important field. This study was subjected to present the method to reduce the pH range of CLSM to a suitable condition that plants can survive. To verify this method, the care of neutralization was conducted by immersing the specimen to Ammonium monohydrogen phosphate. Before curing and neutralization, the maximum pH of developmental CLSM is approximately 11. However, the pH value of developmental CLSM has under 9.5 after peaceful curing and neutralization management.