• Environmental Engineering Research
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• 제16권2호
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• pp.55-60
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• 2011

The removal of hexavalent chromium from aqueous solutions onto modified holly sawdust was studied at varying initial hexavalent chromium concentrations, adsorbent doses, pHs and contact times. The removal of hexavalent chromium from aqueous solutions increased with increasing adsorbent dosage and contact time. The percentage of hexavalent chromium removed from the aqueous solutions decreased with increasing hexavalent chromium concentration and pH of the solution. The kinetics of the adsorption of hexavalent chromium onto modified holly sawdust was analyzed using pseudo first-order and pseudo second-order models. The pseudo second-order model described the kinetics of adsorption of hexavalent chromium. The Langmuir and Freundlich isotherm models were used for modeling of the adsorption equilibrium data. The Langmuir isotherm model well described the equilibrium data for the removal of hexavalent chromium by modified holly sawdust. The obtained maximum adsorption capacity was 18.86 mg/g at pH 7. The results showed that modified holly sawdust can be used as a low cost adsorbent for the treatment of aqueous solutions containing chromium.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제3권2호
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• pp.137-142
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• 1999

One of the most important parameters required to model the absorption of CO2 into aqueous alkanolamine solutions is physical solubility. However, since CO2 reacts in amine solutions, its physical solubility cannot be measured directly. As a result, a nonreacting gas which is similar to CO2 has to be used such as N2O. The solubility of nitrous oxide (N2O) in aqueous solutions of 0wt%-50wt% MDEA, 0wt%-30wt% DEA, and 50wt % total amine with DEA/MDEA molar ratios of 0.05, 0.25, 0.5 and 0.67 was measured using a modified Zipperclave reactor over a temperature range of 293-353 K with near atmospheric partial pressures of N2O. the solubility data from this work were K with near atmospheric partial pressures of N2O. The solubility data from this work were found to be in good agreement with previously reported data where available.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제2권1호
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• pp.79-84
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• 1998

The rates of absorption of carbon dioxide into aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) were measured using a semibatch stirred vessel with a plane gas-liquid interface at $25^{\circ}C.$ The absorption rates under the fast reaction regime were analysed using chemical absorption theory. The reaction was found to be first order with respect to both $CO_2$ and the amine.

• 한국초등과학교육학회지:초등과학교육
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• 제35권1호
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• pp.111-122
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• 2016

The purpose of this study was to investigate elementary school students' awareness about socio-scientific issues and solutions about environmental topics by using their drawings. For this study, 489 students were participated in 3 provincial regions, Incheon, Dangjin and Pohang in Korea. The students participated in a drawing activity to express their ideas of the socio-scientific issues and solutions related to 'environmental problems.' The analysis of the data include that the students displayed most awareness towards air pollution, water pollution and trash problems. However, the global environmental problems such as global warming and climate change were perceived very low. The interesting thing was about 8% of the students, who drew global environmental problems, tried to explain their drawings using scientific knowledge. But they revealed misconceptions as well. For instance, they were not good at connecting their science knowledge with environmental problems. About 80% of the students drew the pictures, showing solutions in personal context. They mainly drew 3 kinds of solutions: 'Reduce trash', 'Preserve ecosystem' and 'Saving of resources & energy'. Most students suggested to administrate the action plans. About 19% of the students drew 'campaign to save the forest' or 'develop alternative energy' in social context. And only 1 student drew UN conference to solve the environmental problems in national context.

• Geomechanics and Engineering
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• 제6권1호
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• pp.65-77
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• 2014

Geosynthetic tubes inflated with water, clay slurry or sand have been widely used for large dike construction in land reclamation projects. In this paper, analytical solutions for geosynthetic tube resting on rigid foundation is presented by adopting an approach similar to that presented by Leshchinsky et al. (1996). The proposed method allows a quick preliminary design to be made for using a closed-form solution. To simplify the analysis, relationships between geometrical parameters and pumping pressure are established using numerical method. The analytical solutions were compared with several existing solutions and good agreements were achieved.

• 환경위생공학
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• 제13권1호
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• pp.112-122
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• 1998

In recent years the accumulation of heavy metals in microorganisms, the biosorption has received much attention because of various environmental application. We have been to research the biosorption characteristics using algae, Spirulina, for the removal of heavy metal ions in industrial and polluted waters. In the adsorption of single heavy metal ions, the adsorption equilibrium was reached within 10min., and optimum pH and reaction temperature were 4.5-5 and 30-35$\circ $C, respectively. Under the above conditions, the maximum amounts of Pb, Cu, and Cd adsorbed to the unit weight of Spirulina were 107.6mg/g, 78.0mg/g, and 65.6mg/g, and three values were 1.45, 1.56, and 1.26 times higher than those adsorbed to the unit weight of activated carbon under same conditions. The adsorption kinetics of Pb, Cu, and Cd were fitted very well to the Freundlich isotherm and BET isotherm. Biosorption experiments in single ion solutions and binary ions solutions showed higher removal efficiency in the single ion solutions than in binary ions solutions.

• 한국환경과학회지
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• 제2권1호
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• pp.79-84
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• 1993

The rates of absorption of carbon dioxide into aqueous solutions of 2-amino-2-methyl-1 propanol (AMP) were measured using a semibatch stirred vessel with a plane gas-liquid interface at $25^{\circ}C$. The absorption rates under the fast reaction regime were analysed using chemical absorption theory. The reaction was found to be first order with respect to both $CO_2$ and the amine.

• Membrane and Water Treatment
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• 제14권1호
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• pp.27-33
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• 2023

In previous studies, solely ferric (Fe³⁺) and calcium (Ca²⁺) ions were commonly used for removal of PO₄-P (considered as T-P in this study) in wastewater via chemical precipitation. Herein, the removal of total phosphorus (T-P) in wastewater was performed using various mineral and lime dissolved solutions. The dissolution kinetics of different minerals (feldspar, olivine, elvan, illite, sericite, and zeolite) and lime was compared and used their solutions for T-P removal of real wastewater. The highest T-P removal (almost 90%) was obtained by the lime dissolved solution and followed by zeolite, illite, feldspar, and others. We observed a significant co-relationship (R of 0.96) between the amount of initial Ca²⁺ and T-P removal. This was induced by formation of hydroxyapatite-like mineral via Ca-P precipitation reaction at high pH solution. Furthermore, additional removal of suspended solid (SS) and chemical oxygen demand (COD) was achieved by only lime dissolved solution. Finally, the lime-feldspar dissolved solutions were prepared at different ratios (10-50%), which showed a successive T-P removal up to two times by samples of 40 and 50%.

• 한국초등과학교육학회지:초등과학교육
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• 제39권3호
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• pp.399-411
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• 2020

This study aims to explore how elementary students perceive and approach the issue of plastic debris in marine habitats by examining students' perspectives on the ecosystem and environmental solutions. The study was conducted to 143 Grade Four elementary school students in Seoul. After implementing two class-units on plastic waste, students' constructed responses on the problem of and solutions to plastic debris in marine habitats were collected. Data were analyzed through semantic network analysis and the keywords were visualized to reflect their relationships. Furthermore, students' responses on how they perceive environmental problems were further analyzed based on the following analysis criteria: students' perspectives on the ecosystem, the level of complexity of food chain(s), and the scope of their perspective. Also, student responses on environmental solutions were classified to be either at a personal or social level. Through semantic network analysis, keywords identified for students' perceptions on the problem were the sea, plastic, debris, animals, living things, humans, extinction, while keywords extracted for the solutions were plastic, debris, recycling, disposable, and I. Based on the analysis criteria, it was found that students were well aware of the food chain concept, could perceive the ecosystem as having comprised of both biotic and abiotic factors, and could approach the problem beyond the scope of the marine environment. Also, most students mentioned the solutions only at a personal level. Based on the findings, implications on how to move forward in educating environmental issues related to the ecosystem in science education is further discussed.

• 자원환경지질
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• 제53권1호
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• pp.11-21
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• 2020

본 연구는 대수층과 저투수층이 존재하는 단일시스템에서 trichloroethylene (TCE)과 tetrachloroethylene (PCE)의 거동에 대해 1차원 확산 해석해를 사용하여 저투수층의 농도 분포, 대수층과 저투수층의 경계면에서 확산 선속, 그리고 역확산에 의한 대수층의 오염 지속성을 모델링하였다. 모델링에 사용된 해석해는 이전 연구에서 많이 사용되었던 저투수층의 두께가 무한한 조건의 해석해와 본 연구에서 제시한 저투수층의 두께가 유한한 조건을 고려한 해석해를 모두 사용하였다. 제시된 해석해의 타당성을 평가하기 위해 저투수층의 두께가 무한한 조건의 해석해와 Yang et al.(2015)이 개발한 1차원 확산 해석해의 결과를 Nash-Sutcliffe 유효계수(NSE)로 비교하였다. 저투수층의 농도 분포, 확산 선속, 그리고 대수층의 오염 지속성 등 모든 결과에서 무한한 조건의 해석해를 이용하였을 때 과소평가되는 결과를 나타내었다. 그리고 본 연구에서 제시한 해석해의 결과와 Yang et al. (2015)이 개발한 해석해의 결과는 높은 일치성(NSE = 0.99)을 보였다. 본 연구에서 제시한 해석해를 실제 오염된 부지에 효율적으로 적용하기 위해 유효확산계수, 저투수층의 두께, 그리고 확산된 시간을 이용하여 확산 거리(Z_d)라는 용어를 소개하였다. 확산 거리가 0.7 보다 작은 경우 저투수층의 두께가 무한한 조건의 해석해를 사용할 수 있으며, 확산 거리가 0.7 보다 큰 경우 저투수층의 두께가 유한한 확산 해석해를 사용하여야 모델링의 신뢰성을 높일 수 있을 것으로 사료된다.