Gelation Dynamics of Ionically Crosslinked Alginate Gel with Various Cations

권석현,선정윤,윤주일,석현광,오규환 한국고분자학회 2015 Macromolecular Research Vol.23 No.12

Alginates can be crosslinked with multivalent cations, leading eventually to hydrogel formation. The properties of alginate gel depend on its lock structure, monomeric composition, concentration of polymer and cross linker. Among these, the properties of ionically crosslinked alginate gel can be greatly affected by multivalent cations as cross-linker. Knowledge of gelation dynamics by multivalent cations allows control over gelation characteristics, such as modulus of gel and the time required for equilibrium state, and healing properties. We have studied gelation dynamics of ionically crosslinked alginate gel. According to different types of anions bound with cations, gelation time and equilibrium viscosity was changed due to the solubility kinetics of the cation. The equilibrium viscosity is increased as the size of the cations increased even though the cations have same valency. A theoretical model is introduced to interpret dynamic change of viscosity during gelation.

Simultaneous Determination of Anions and Cations in Natural Water by Ion-exclusion/Cation-exchange Chromatography with a Weakly Acidic Cation-exchange Resin Column

Lee, Kwang-Pill,Choi, Seong-Ho,Park, Yu-Chul,Bae, Zun-Ung,Lee, Mu-Sang,Lee, Sang-Hak,Chang, Hye-Yong,Kwon, Se-Mok,Kazuhiko Tanaka Korean Chemical Society 2003 Bulletin of the Korean Chemical Society Vol.24 No.9

The simultaneous determination of anions ($SO_4 ^{2-},\;Cl^-,\;and\;NO_3^-$) and cations ($Na^+,\;NH^{4+},\;K^+,\;Mg^{2+},\;and\;Ca^{2+}$) in natural water obtained by Nakdong River waters system in Korea were performed by ion-exclusion/cationexchange chromatography with conductimetric detection. The stationary phase was a polymethacrylate-based weakly acidic cation-exchange resin column in the $H^+$-form and a weak-acid eluent. When using only a 1.4 mM sulfosalicylic acid/6 mM 18-crown-6 ether as an eluent, good resolution of both anions and cations, minimum time required for the separation, and satisfactory detection sensitivity were obtained in a reasonable time. The method was successfully applied to the simultaneous determination of anions and cations in natural waters.

Molecular Dynamics Simulation and Density Functional Theory Investigation for Thiacalix[4]biscrown and its Complexes with Alkali-Metal Cations

Jooyeon Hong,이제욱,함시현 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.2

The structural and energetic preferences of thiacalix[4]biscrown-5 with and without alkali metal ions (Na+, K+, Rb+and Cs+) have been theoretically investigated for the first time using molecular dynamic (MD) simulations and density functional theory (MPWB1K/6-31G(d)//B3LYP/6-31G(d)) methods. The formation of the metal ion complex by the host is mainly driven by the electrostatic attraction between crown-5 oxygens and a cation together with the minor contribution of the cation-π interaction between two facing phenyl rings around the cation. The computed binding energies and the atomic charge distribution analysis for the metal binding complexes indicate the selectivity toward a potassium ion. The theoretical results herein explain the experimentally observed extractability order by this host towards various alkali metal ions. The physical nature and the driving forces for cation recognition by this host are discussed in detail.

Molecular Dynamics Simulation and Density Functional Theory Investigation for Thiacalix[4]biscrown and its Complexes with Alkali-Metal Cations

Hong, Joo-Yeon,Lee, Che-Wook,Ham, Si-Hyun Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.2

The structural and energetic preferences of thiacalix[4]biscrown-5 with and without alkali metal ions ($Na^+$, $K^+$, $Rb^+$, and $Cs^+$) have been theoretically investigated for the first time using molecular dynamic (MD) simulations and density functional theory (MPWB1K/6-31G(d)//B3LYP/6-31G(d)) methods. The formation of the metal ion complex by the host is mainly driven by the electrostatic attraction between crown-5 oxygens and a cation together with the minor contribution of the cation-$\pi$ interaction between two facing phenyl rings around the cation. The computed binding energies and the atomic charge distribution analysis for the metal binding complexes indicate the selectivity toward a potassium ion. The theoretical results herein explain the experimentally observed extractability order by this host towards various alkali metal ions. The physical nature and the driving forces for cation recognition by this host are discussed in detail.

토양의 유효태 인산과 치환성 양이온의 다성분동시추출 분석방법 비교

김명숙(Myung-Sook Kim),양재의(Jae Eui Yang),김유학(Yoo-hak Kim),윤정희(Jung-Hui Yoon),장용선(Yong-Seon Zhang),곽한강(Han-Gang Kwak),하상건(Sang-Keon Ha),현병근(Byung-Keun Hyun) 한국토양비료학회 2009 한국토양비료학회지 Vol.42 No.3

과학영농과 친환경농업이 대두되면서 토양검정량이 급속하게 증가하고 이에 대처하기 위해 신속하게 분석할 수 있는 분석 방법이 요구되고 있다. 따라서 본연구에서는 신속·간편하게 분석할 수 있는 다성분동시추출방법으로 개발된 Mehlich Ⅲ법, Mod. Morgan법, Kelowna 법과 국내에서 사용 중인 유효태 인산분석법인 Lancaster법 , 치환성 양이온 분석법인 1MNH4OAc법으로 분석되는 분석치들 간의 상관관계를검토하기 위하여 토양특성이 다양한 우리나라 농경지115개소에서 토양을 채취하여 여러 가지 방법으로 화학적 분석을 실시하였다. 다성분동시추출 분석방법인 Mehlich Ⅲ법, Mod. Morgan법, Kelowna법과 기존의 유효인산 분석방법인 Lancaster법과 치환성 양이온 분석방법인 1M NH4OAc법으로 추출한 분석치는 모두 고도로 유의한 직선적인 상관관계에 있었다. 유효인산은 Mehlich Ⅲ법, Mod. Morgan법, Kelowna 법과 Lancaster법으로 추출되는 분석치간에 결정계수(R<SUP>2</SUP>)의 크기는 MehlichⅢ법(0.979<SUP>***</SUP>) > Kelowna법(0.977<SUP>***</SUP>) > Mod. Morgan법(0.553<SUP>***</SUP>)의 순으로 MehlichⅢ 법 이 상 관 이 가 장 높 게 나타났고 Lancaster 법보다 토양 중의 인산을 평균적으로 28% 많이 추출하였다. 치환성 양이온에서도 화산회 토양에서 추출되는 나트륨 성분을 제외하고는 Mehlich Ⅲ법으로 추출되는 분석치가1MNH4OAc법으로 추출되는 것과 가장 상관이 높았다. 따라서 ICP를 이용하여 유효인산과 치환성 양이온의 분석은 다성분동시추출방법인 Mehlich Ⅲ법이 이용 가능할 것으로 판단되었다. Soil testing is one of the best management practices for sustainable agriculture. Recently, as increasing soil testing needs, simplification of soil analytical procedure has been required. To determine recommendable multi-element extractant, the soil testing results of available phosphate and exchangeable cations between the conventional method(Lancasterand1MNH4OAc) and multi-element extraction methods such as Mehlich Ⅲ, Modified Morgan and Kelowna methods were compared. There were highly significant correlation between the conventional methods and multi-element extraction methods (Mehlich Ⅲ, Modified Morgan and Kelowna) for available phosphate and exchangeable K, Ca, Mg and Na. The coefficients of determination (R<SUP>2</SUP>) between available phosphate extracted by Lancaster method and multielement extraction methods were in the order of MehlichⅢ (0.979<SUP>***</SUP>) > Kelowna (0.977<SUP>***</SUP>) > Modified(Mod.). Morgan (0.553<SUP>***</SUP>). For exchangeable cations, there were highly significant correlations between 1M NH4OAc method and Mehlich Ⅲ, Mod. Morgan and Kelowna. However, exchangeable K, Ca and Mg by Mehlich III method were more highly correlated with conventional method than other methods. Therefore, Mehlich III extraction method could be recommended as a single extractant for simultaneous measurement using ICP in the analysis of avaliable phosphate and exchangeable cations.

양이온교환막 표면의 전기투석 물분해에서 다가의 큰 이온성분자에 의해 형성된 고정층 바이폴라 계면의 영향

Seung Hyeon Moon,Moon Sung Kang,Yong Jin Choi 한국막학회 2003 멤브레인 Vol.13 No.3

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. The effects of bipolar interface formed on the surface of cation-exchange membrane on water splitting phenomena were investigated. Results showed that the formation of immobilized bipolar interface resulted in significant water splitting during electrodialysis. In particular, the immobilized bipolar interface was easily created on the cation-exchange membrane surface in the electrodialytic systems where multivalent cations served as an electrolyte. Multivalent cations with low solubility product resulted in violent water splitting because they were easily precipitated on the membrane surface in hydroxide form. Therefore, the bipolar interface consisting of H- and OH-affinity groups were formed on the membrane-solution interface. Apparently, water splitting was largely activated with the help of strong electric fields generated between the metal hydroxide layer and fixed charge groups on the membrane surface. Likewise, the accumulation of large molecular counter ions on the membrane surface led to the formation of a fixed bipolar structure that could cause significant water splitting in the over-limiting current region. Therefore, the prevention of the immobilization of bipolar interface on the membrane surface is very essential in improving the process efficiency in a high-current operation.

Extraction and preconcentration of nickel, cadmium, cobalt, and lead cations using dispersive solid phase extraction performed in a narrow-bore tube

Mir Ali Farajzadeh,Adeleh Yadeghari 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.59 No.-

A new version of DSPE in a narrow-bore tube followed by HPLC-DAD was proposed for the analysis of Ni2+, Cd2+, Co2+, and Pb2+ cations. 2-Propanol is mixed with C18 sorbent and used for dispersing the sorbent into solution containing the cations oxinate complexes. The sorbent passes through the solution in a short time versus passing the solution from the cartridge which is done in the conventional SPE in a long time. In comparison to SPE, the active surface area is larger because of preventing sorbent clogging. EFs and LODs were obtained in the ranges of 831–1073 and 0.05–0.40 μg L−1, respectively.

Effects of Chemical Stabilizers on an Expansive Clay

Honghua Zhao,Louis Ge,Thomas M. Petry,Yi-Zhen Sun 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.4

Expansive clays exhibit a high potential for the volume change behavior when the soil moisture changes. The estimated annualcost of the damage to the facilities built on expansive clay in the United States exceeds 9 billion dollars. Because of the physicochemicalnature of the expansive clay, the use of chemical agents to improve their engineering properties is common. This researchinvestigated the effects of chemical agents on an expansive soil from Texas through a laboratory injection method. The agents used inthis study included lime, potassium based agents, and a group of ionic agents. Swelling tests, chemical tests, and soil suction testswere used to evaluate the stabilizing effects of those chemical agents. The testing results indicated that potassium based stabilizer, isan effective stabilizing agent to control the swelling potential of the expansive clay. It can also be injected in the field to build amoisture barrier. The chemical tests on the injected Texas clay showed that the stabilizing mechanism of the ionic agents is possiblythrough the cations’ exchange and the increase of the cations’ concentrations in the soil pore water.

An Investigation of Characteristics of Chinese Bellflower (Platycodon grandiflorum A.) Cultivated Soil

최장남,이왕휴 한국자원식물학회 2018 한국자원식물학회지 Vol.31 No.6

In order to understand the characteristics of soil according to the cultivation environment of Chinese bellflower(Platycodon grandiflorum A.), soil chemical properties of 12 collected soil samples from 6 cultivated fields in Okcheon,Chungbuk province in August. 2017 were analyzed. The soil pH was distributed within the range of 4.61 to 5.25 at allcultivation years and E.C (Electric Conductivity) and T-N (Total Nitrogen) of the cultivation year were not significant. Available P2O5 was higher than the average for medicinal crops and P. grandiflorum in Korea and C.E.C (Cation ExchangeCapacity) was inconsistent for each cultivation year. In particularly, it was validated that the content of exchangeablecations K, Ca, Ma, and Na in this experiment was similar to that of C.E.C according to the cultivation years, because C.E.Chad a high correlation with the exchangeable cations. For the available P2O5, as affected by trans-planting, 5Y-NT-H(cultivated 5 years and non-transplanted) had 58 mg/kg, while 5Y-T-H (cultivated 5 years and transplanted) had 246 ㎎/㎏. The soil pH was found to be lower (acidic) in diseased soils than healthy soils. E.C was confirmed to be was higher indiseased soils than healthy soils except for the one cultivated for 2 years. The contents of T-N and available P2O5 werehigher in diseased soil except for the one cultivated for 5 years and 11 years. The exchangeable cation K and Na tended tobe higher in diseased soils rather than that in healthy soils, and the exchangeable cation Ca and Mg contents were higher inhealthy soils than in diseased soils. The C.E.C of the soil was lower than that of healthy soils in all of the years except for theone which was cultivated for 5 years (transplanted).

Size effects of imidazolium cations bearing cyanoethyl group on performance of dye-sensitized solar cells

Song, Donghoon,Choi, Young-Seop,Kim, Byung Su,Kim, Hoon Sik,Kang, Yong Soo Elsevier 2019 Materials letters Vol.246 No.-

<P><B>Abstract</B></P> <P>Imidazoliums are commonly used ionic liquid cations in electrolyte in dye-sensitized solar cells (DSSCs). Here, the size effects of imidazolium cations bearing the cyanoethyl group on DSSC performance have been systematically investigated by introducing the different alkyl chains (C1–C12), by which size control is allowed in a range of 9–20 Å. The large cations slow down electron recombination and ion diffusion, but, unexpectedly, they suppress downward shift of TiO<SUB>2</SUB> conduction band significantly affecting on electron injection process. While all the cations used in this work demonstrate a better power conversion efficiency than that for the common imidazolium analogue, the interplay among the key processes results in the best performance with the medium-sized cation C4 (11 Å). This work paves a way for design of efficient electrolyte cations for photovoltaic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Imidazolium ionic liquids are utilized in electrolytes in dye-sensitized solar cells. </LI> <LI> Cations in the ionic liquids are differently sized while bearing cyanoethyl group. </LI> <LI> Bulky cations exhibit slow I<SUB>3</SUB> <SUP>−</SUP> diffusion and electron recombination. </LI> <LI> But, unexpectedly, bulky cations suppress downward shift of TiO<SUB>2</SUB> conduction band. </LI> <LI> This interesting result is closely associated with function of cyanoethyl group. </LI> </UL> </P>