• 멤브레인
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• 제13권3호
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• pp.143-153
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• 2003

본 연구에서는 양이온교환막 표면에 형성된 바이폴라 계면이 물분해 현상에 미치는 영향을 조사하였다. 실험결과, 전기투석 중 막표면에 형성된 고정화된 바이폴라 계면이 심각한 물분해를 유발함을 알 수 있었다. 특히, 고정화된 바이폴라 계면은 다가 양이온이 전해질로 이용되는 전기투석 시스템에서 양이온교환막 표면에 쉽게 형성됨을 알 수 있었다. 낮은 용해도적 상수를 갖는 다가 양이온들은 급격한 물분해를 유발하였는데 이는 이들이 막표면에서 쉽게 수산화물의 형태로 침적되며 따라서 수소-친화 그룹과 수산화-친화 그룹으로 구성된 바이폴라 계면이 막-용액 계면에 형성됨을 알 수 있었다. 따라서 물분해는 막 표면의 금속수산화물 층과 막의 고정전하 그룹간에 발생되는 강한 전기장에 의해 크게 활성화됨을 알수 있다. 또한 이와 유사하게 분자량이 큰 유기 상대이온들이 막표면에 누적되는 경우에도 고정화된 바이폴라 계면이 형성되어 한계전류밀도 이상에서 심각한 물분해를 유발하였다. 따라서 전기투석의 고전류 운전시 효율 향상을 위해서는 막표면에 유발되는 고정화된 바이폴라 계면의 형성을 억제하는 것이 매우 중요함을 알 수 있다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권6호
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• pp.460-464
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• 2000

Extracellular polymeric substances (EPS) are believed to play a role in the binding and formation of microbial flocs. However, the precise role is not well known. Sludge settling characteristics and the carbohydrate to protein ratio in EPS were tested with various airflow rates in this study. Sludge was collected from three modified sequencing batch reactors (SBRs), which were operated at 16$\^{C}$ with an airflow rate of 0.8L/min, 3L/min and 6L/min, respectively. During the operation, the reactor operated at an airflow rate of 0.8L/min showed sludge volume index (SVI) of 80 to 90ml/g and a constant ratio of carbohydrate to protein in the EPS, while a significant increase in the SVI was seen in the other reactors. Sludge bulking increased the amount of carbohydrate in the EPS, while kept protein almost constant in the airflow rate of 3L/min ad 6L/min. Surface charge also increased with increases in the carbohydrate to protein ratio in the EPS, which weakens the attraction between the EPS and multivalent cations. The ratio of carbohydrate to protein in the EPS was tween the EPS and multivalent cations. The ratio of carbohydrate to protein in the EPS was inferred to be essential for bioflocculation.

• Archives of Pharmacal Research
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• 제8권2호
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• pp.91-98
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• 1985

Dependence of the flow behavior of aqueous suspension of Young-Il bentonite on the concentration and the type of electrolytes was studied. Viscosity measurements were made was Rion Viscotester, using No. 3 rotor at 62.5 R. P. M. at 25.deg.C. As electrolyte concentration increased, the apparent viscosity was observed to increase. Changes in viscosity were in general agreement with predicted results based on the Hofmeister sequence and the Schulze-Hardy rule. The observed electrolyte effect on the apparent viscosity was discussed in terms of the Verwey-Overbeek theory.

• 대한화학회지
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• 제15권6호
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• pp.303-312
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• 1971

Dependence of the flow behavior of aqueous suspension of Black Hills bentonite on the concentration and the types of electrolytes was stydied. The flow properties were measured with a Couette-type totational viscometer. On addition of monovalent cations, the apparent viscosity determined from the reproducible flow curves (shear rate vs. shear stress) decreased followed by a rise as the ionic concentration further increased. Addition of multivalent cations (di- and tri-) resulted in the viscosity which increased to a maximum then decreased to a constant value. Anions of different chatges produced essentially the same relationship between viscosity and electrolyte concentration. The flow behavior of the electrolyte-containing suspensions was rationalized in terms of the Derjaguin-Landau-Verwey-Overbeek theory of colloidal stability and the generalized theory of viscosity.

• Bulletin of the Korean Chemical Society
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• 제32권12호
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• pp.4316-4320
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• 2011

The effects of various hydroxide compounds on base stacking (BS) were investigated for pre-concentration of DNA molecules in capillary electrophoresis (CE). In BS, hydroxide ions ($OH^-$) were electrokinetically introduced after DNA sample injection. A neutralization reaction occurred between the $OH^-$ and $Tris^+$ of the running buffer, which resulted in a zone of lower conductivity. Within the low conductivity zone of the high electric field, the DNA molecules moved more rapidly and were concentrated in front of the low conductivity zone. At the same BS conditions of CE, the enhanced sensitivity of the DNA samples was dependent on the kind of multivalent cations in the hydroxide compounds. Except for LiOH, the hydroxide compounds with monovalent cations showed more effective BS than those with divalent cations because of solubility, ionic strength and electronegativity. The order of hydroxide compounds that enhance the detection sensitivity of DNA molecules was as follows: NaOH > $NH_4OH$ > KOH > $Ba(OH)_2$ > $Sr(OH)_2$ > LiOH > $Ca(OH)_2$ > $Mg(OH)_2$. $NH_4OH$, KOH and $Ba(OH)_2$ proved to be efficient hydroxide compounds to use as effective BS reagents in CE instead of NaOH.

• Macromolecular Research
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• 제13권6호
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• pp.483-490
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• 2005

A novel, polysaccharide-based, superabsorbent hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto kappa-carrageenan ($_{k}C$), using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. A proposed mechanism for $_{k}C$­g-polymethacrylic acid ($_{k}C$-g-PMAA) formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The effect of grafting variables, including MBA, MAA, and APS concentration, was systematically optimized to achieve a hydrogel with the maximum possible swelling capacity. The swelling kinetics in distilled water and various salt solutions were preliminarily investigated. Absorbency in aqueous salt solutions of lithium chloride, sodium chloride, potassium chloride, calcium chloride, and aluminum chloride indicated that the swelling capacity decreased with increased ionic strength of the swelling medium. This behavior can be attributed to the charge screening effect for monovalent cations, as well as ionic crosslinking for multivalent cations. The swelling of super absorbing hydrogels was measured in solutions with pH ranging from 1 to 13. In addition, the pH reversibility and on-off switching behavior, at pH levels of 3.0 and 8.0, give the synthesized hydrogels great potential as an excellent candidate for the controlled delivery of bioactive agents.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1993년도 지반.환경 매립에 관한 학술발표회 논문집
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• pp.28-44
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• 1993

Remediation actions in uncontrolled landfill site should be conducted after the investigation of contamination status and potential health risk or damage. Based on the above, proper control measures should be established and operated. Also continuous monitoring should be followed. In this study, the status of ground water contamination around Nanji Landfill Site was investigated. Monitoring wells were installed around the landfill and ground water was sampled once a month and analyzed. Water quality of each monitoring well was different depending on the horizontal and vertical distance from the landfill, and the seasonal leachate characteristics were not significantly changed because percolating water stayed long time in the deep waste layer. It was predicted that major multivalent cations were mainly precipitated as metal carbonate form, and chemical mass balances (CMBs) could be applied for the apportionment of leachate contamination to ground water quality of surrounding areas of Nanji Landfill. Parameters required to estimate pollutant flux to the receptor near landfill were listed and discussion to get these parameters was made. Finally, based on the above data, control measures of ground water contamination were suggested and discussed.

• Macromolecular Research
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• 제13권1호
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• pp.45-53
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• 2005

In this study, a series of highly swelling hydrogels based on sodium alginate (NaAlg) and polymethacryl­amide (PMAM) was prepared through free radical polymerization. The graft copolymerization reaction was performed in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator and N,N'-methylenebis­acrylamide (MBA) as a crosslinker. The crosslinked graft copolymer, alginate-graft-polymethacrylamide (Alg-g­PMAM), was then partially hydrolyzed by NaOH solution to yield a hydrogel, hydrolyzed alginate-graft-poly­methacrylamide (H-Alg-g-PMAM). During alkaline hydrolysis, the carboxamide groups of Alg-g-PMAM were converted into hydrophilic carboxylate anions. Either the Alg-g-PMAM or the H-Alg-g-PMAM was characterized by FTIR spectroscopy. The effects of the grafting variables (i.e., concentration of MBA, MAM, and APS) and the alkaline hydrolysis conditions (i.e., NaOH concentration, hydrolysis time, and temperature) were optimized systematically to achieve a hydrogel having the maximum swelling capacity. Measurements of the absorbency in various aqueous salt solutions indicated that the swelling capacity decreased upon increasing the ionic strength of the swelling medium. This behavior could be attributed to a charge screening effect for monovalent cations, as well as ionic cross-linking for multivalent cations. Because of the high swelling capacity in salt solutions, however, the hydrogels might be considered as anti-salt superabsorbents. The swelling behavior of the superabsorbing hydrogels was also measured in solutions having values of pH ranging from 1 to 13. Furthermore, the pH reversibility and on/off switching behavior, measured at pH 2.0 and 8.0, suggested that the synthesized hydrogels were excellent candidates for the controlled delivery of bioactive agents. Finally, we performed preliminary investigations of the swelling kinetics of the synthesized hydrogels at various particle sizes.

• Ecology and Resilient Infrastructure
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• 제4권1호
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• pp.63-70
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• 2017

가축용 항생제로 널리 사용되는 Tetracycline (TC)군은 주로 가축 분뇨를 통하여 환경에 퍼지게 된다. TC는 환경 내에서 중금속 양이온과의 리간드 결합을 통해 토양으로의 흡착량과 그 이동성이 변화되리라 예측된다. 그러나 지금까지 수용액 내에서 토양 외 반응을 통해 확인되었고 토양 내에서 식물에 대한 영향 평가는 미비한 실정이다. 본 연구의 목적은 토양 내 구리가 TC와 반응하여 TC에 의한 식물 독성에 미치는 영향을 확인하는데 있다. 본 실험은 토양에 $750mg\;kg^{-1}$의 TC와 각각 0, 2.5, 7.5, $17.5mg\;kg^{-1}$의 $CuSO_4$를 처리한 후, 처리된 토양에 상추를 재배하여 처리 농도에 따른 상추의 성장 정도를 비교하였다. 실험 결과 상추에 유의한 독성이 나타나는 것으로 확인된 $750mg\;kg^{-1}$의 TC가 처리된 토양에서 구리의 처리가 상추에 발현되었던 독성을 저감시키는 것을 확인하였다.

• 멤브레인
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• 제32권4호
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• pp.209-217
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• 2022

이온교환막(IEM)은 다양한 종류의 단가이온과 다가이온을 분리하기 위해 사용되는 막의 한 종류로, 배터리, 연료전지, 염화물-알칼리 공정 등에 사용된다. 이온교환막을 통한 막분리는 전기 구동력을 기반으로 한 녹색 분리 방식이며, 해수 담수화와 수처리 분야에서 떠오르는 방식이다. 전기투석(ED)은 양이온과 음이온이 이온교환막을 따라 선택적으로 이동하는 기술이다. 음이온 교환막(AEM)은 전기투석의 중요한 구성 요소 중 하나이며, 공정 효율을 향상시키는 데 상당한 역할을 한다. 이온교환막에 가교결합을 도입하면 자유 부피의 감소로 인해 이온 선택 분리 성능이 향상된다. 역삼투(RO) 공정을 통한 해수 담수화 시 RO 농축수에 용해된 염이 다량 존재한다. 따라서 1가 양이온 선택막으로 구성된 전기투석 공정은 오염을 줄이고 막 플럭스를 개선한다. 이 검토는 전기투석, 음이온 교환막, 그리고 양이온 교환막의 세 부분으로 나뉜다.