• Environmental Engineering Research
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• 제25권4호
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• pp.536-544
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• 2020

To address organic dye wastewater, economic and effective adsorbents are required. Here, magnetic biochar from alkali-activated rice straw (AMBC) was successfully synthesized using one-step magnetization and carbonization method. The alkaline activation caused the large specific surface area, high pore volume and abundant oxygen-containing groups of the AMBC, and the magnetization gave the AMBC a certain degree of electropositivity and fast equilibrium characteristics. These characteristics collectively contributed to a relative high adsorption capacity of 53.66 mg g^-1 for this adsorbent towards rhodamine B (RhB). In brief, RhB can spontaneously adsorb onto the heterogeneous surface of the AMBC and reach the equilibrium in 60 min. Although the initial pH, ionic strength and other substances of the solution affected the adsorption performance of the AMBC, it could be easily regenerated and reused with considerable adsorption content. Based on the results, H-bonds, π-π stacking and electrostatic interactions were speculated as the primary mechanisms for RhB adsorption onto the AMBC, which was also demonstrated by the FTIR analysis. With the advantageous features of low cost, easy separation, considerable adsorption capacity and favorable stability and reusability, the AMBC would be a potential adsorbent for removing organic dyes from wastewater.

• 한국재료학회지
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• 제14권6호
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• pp.407-412
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• 2004

Photo decomposition of gas phase benzene by $TiO_2$ thin films chemically deposited on alumina balls were investigated under UV irradiation. Photo decomposition rates were measured in real time during the reaction using a photo ionization detector, which ionizes C-H bonding of benzene molecules and then converts into volatile organic compounds (VOCs) concentrations. From the measuring results, the VOCs concentration increased instantly when IN irradiated because C-H bonds of benzene molecules strongly absorbed on the surface of $TiO_2$ films before the IN irradiation was destroyed by photo decomposition. After that, the VOCs concentration decreased with increasing surface area of $TiO_2$ and reaction time under the IN irradiation. At the optimal conditions for the photo decomposition of gas phase benzene, the reaction rate of the photo decomposition for high concentrations (over 60 ppm) was slow but that of relatively low concentration (under 60 ppm) was fast, due to limited surface area of $TiO_2$ thin films for the reaction. Thus, it is concluded that the photo decomposition rate was mainly affected by the surface area of $TiO_2$ or absorption reaction.

• Korean Chemical Engineering Research
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• 제40권6호
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• pp.735-740
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• 2002

고분자 필름의 무적성을 향상시키기 위하여 우수한 친수성 및 높은 가시광선 투과율을 보이는 유기-무기 혼성 코팅용액을 졸-겔법으로 합성하였다. 코팅용액은 입자 직경이 15 nm 크기의 무기물인 콜로이드 실리카 용액(Ludox)에 유기 조성을 함유한 화합물인 GPS을 첨가하여 제조되었다. 실란 커플링제인 GPS는 콜로이드 실리카와 주변의 매트릭스(matrix)인 고분자 필름에 각각 강한 결합을 형성하여 두 개의 서로 다른 물질을 강하게 연결하는 결합제 역할을 한다. 강산성 조건 하에서 제조된 혼성 코팅용액으로 고분자 필름 위에 코팅한 경우는 코팅필름의 표면이 거의 균열이 없는 매끈한 미세구조를 보이는 반면, 약산과 염기성 조건 하에서 제조된 혼성 코팅용액으로 코팅한 경우에는 균열이 심한 미세구조를 보였다. 또한 pH 2의 산성 조건에서 제조한 필름은 우수한 친수성 및 높은 가시광선 투과율을 보인 반면, 염기성 조건으로 제조한 코팅필름은 친수성이 좋지 않았으며, 낮은 가시광선 투과율을 보였다.

• Bulletin of the Korean Chemical Society
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• 제29권4호
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• pp.790-794
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• 2008

Nucleophilic addition reaction of benzenethiols (PhSH) to 1-(2-nitrovinyl) benzenes ($\beta$ NS) in the presence of triethylamine (TEA) has been studied in acetonitrile at 25 ${^{\circ}C}$. The rate is first order with respect to [PhSH], [TEA] and [$\beta$ NS]. The reaction is found to proceed with the formation of ion-pair between benzenethiol and TEA. A suitable mechanism with the formation of an adduct between ion-pair and substrate in a slow step followed by its rearrangement to 1,2-addition product in a fast step has been proposed and corresponding rate law derived. From the rate law, the rate constants for the interaction between ion-pair and $\beta$NS have been evaluated. Interestingly, in both para-substituted substrates and benzenethiols the rate increases with the electron-withdrawing power of the substituents. The positive sign of $\rho_x$ in benzenethiols has been explained. The magnitude of cross-interaction constant, $\rho_{xy}$ is small (0.08). The magnitude of the Hammett $\rho_x$ values is higher than that of the Bronsted, $\beta_x$ values for benzenethiols. The kinetic isotope effect, $k_H/k_D$, is found to be greater than unity. A suitable transition state with simultaneous formation of $C_\beta$ -H and $B_\alpha$ -S bonds involving the ion-pair and $\beta$NS in a single concerted step has been proposed to account for these observations.

• 농업과학연구
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• 제35권1호
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• pp.11-17
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• 2008

가시오가피를 실온에서 petroleum ether로 추출한 polyacetylene의 동정하기 위하여 TLC, HPLC, UV spectrum, IR, NMR로 수행하였다. TLC에 전개시킨 결과, polyacetylene 표준품과 동일한 band가 fraction 5에서 확인되었으며, HPLC에서 fraction 5를 분리시킨 결과 retention time이 4.40, 5.36, 6.40분이었다. 이를 UV spectrum에서 확인한 결과, 6.40분의 peak(compound 3)에서 polyacetylenes의 파장인 231.0nm, 239.0nm, 257.0nm을 나타내었다. IR spetrum에서 triple bond $2256cm^{-1}$과 double bond $1654cm^{-1}$의 전형적인 peak를 나타내었으며, $^{13}C$-NMR(400MHz, $CDCl_3$)에서 polyacetylenes 전형적인 64.0, 71.2, 74.2, 80.2ppm은 2개의 triple bond에 의한 peak와 121.89, 133.0ppm에서 internal double bond로 결합된 2개의 peak를 확인 할 수 있었다.

• 한국결정학회지
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• 제15권2호
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• pp.74-77
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• 2004

Dinitroethylenediaminepalladium(II), $Pd(C_2H_8N_2)\;(NO_2)_2$의 결정구조는 a=7.425(3), b=8.480(4), c=11.885(2)${\AA}$, 사방정계(Orthorhombic), 공간군 $A2_1ma$, 공간군 번호 36이며, Z=4, V=748.3(4)${\AA}^3,\;D_c=2.295\;gcm^{-3},\;{\mu}=2.457mm^{-1}$이었다. 구조분석은 중금속법으로 풀었으며, 최소 자승법으로 정밀화하였고, 최종 신뢰도 값들은 377개의 회절반점에 대하여 $(R_1=0.0306,\;R_w=0.0802,\;R_{all}=0.0320,\;S=1.166)$이었다. 최종 분석한 착염의 결합거리와 각들은 기존에 알려진 해당 자료들에 상응하였다. 착염의 구조는 Reiset's salt type 유사체와 같은 일차원 구조로써 c축을 따라서, Pd-Pd 거리가 3.762(2) $(\AA)$이고, 각 $161.41(5)^{\circ}$인 지그재그 사슬구조를 형성하고 있다. 사슬내에서나 사슬간에는 질소와 산소사이에 각각 3.05(1)과 3.15(1) ${\AA}$인 수소결합으로 연결되어 있다.

• 통합자연과학논문집
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• 제3권1호
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• pp.1-6
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• 2010

Bis(silyl)alkylbenzenes such as bis(1-sila-sec-butyl)benzene (1) and 2-phenyl-1,3-disilapropane (2) were synthesized in high yields by the reduction of the corresponding chlorosilanes with $LiAlH_4$ in diethyl ether. The dehydrocoupling of 1 and 2 was performed using group IV metallocene complexes generated in situ from $Cp_2MCl_2$/Red-Al and $Cp_2MCl_2$/n-BuLi (M = Ti, Hf), producing two phases of polymers. The TGA residue yields of the insoluble polymers were in the range of 64-74%. The molecular weights of the soluble polymers produced ranged from 700 to 5000 ($M_w$ vs polystyrene using GPC) and from 500 to 900 ($M_w$ vs polystyrene using GPC). The dehydropolymerization of 1 and 2 seemed to initially produce a low-molecular-weight polymer, which then underwent an extensive cross-linking reaction of backbone Si-H bonds, leading to an insoluble network polymer.

• 접착 및 계면
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• 제14권3호
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• pp.128-134
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• 2013

본 연구에서는 합성수지 접착제를 대체하여 토기 유물에 활용할 수 있는 천연접착제를 개발하기 위해 옻과 아교를 배합하여 시료를 제조하였고 이에 대한 구조적 물리적 특성을 분석하였다. 구조분석 결과 옻에 배합하는 아교의 비율이 높아질수록 carbonyl (C=O), amine (N-H), aromatic (C=C) 결합이 증가하는 것을 확인하였다. 또한 제조한 천연접착제를 합성수지 접착제와 비교하였을 때 낮은 접착강도를 가진 Paraloid B-72부터 높은 접착강도의 Araldite rapid type에 상응하는 다양한 점도와 접착강도를 가지고 있음을 확인하였다. 이를 바탕으로 하여 향후 체계적이고 심화된 분석이 이루어 진다면 훼손된 토기 유물의 접착 및 복원을 위한 친환경 천연접착제의 실용화가 가능할 것으로 사료된다.

• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3777-3787
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• 2012

Three kinds of 3D isomorphous and isostructural coordination polymers, namely, $\{[Ln_2(PDA)_3(H_2O)_3]{\cdot}0.25H_2O\}_{\infty}$ (Ln = La(1), Sm(2), and Gd(3)) ($PDA^{2-}$ = pyridine-2,6-dicarboxylate anion) have been synthesized under hydrothermal conditions and characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. In these MOFs, Ln(III) centers adopt eight-coordinated and nine-coordinated with the $N_1O_7$ and $N_2O_7$ donor sets to construct distorted trianglar dodecahedron geometry and tricapped trigonal prism configurations, respectively. Based on the building block of tetranuclear homometallic $Ln_4C_4O_8$ unit (16-membered ring), 1-3 are connected into highly ordered 2D sheets via O-C-O linkers and further constructed into 3D architectures through hydrogen bonds. Crystallographic parameters suggest that the lanthanide contraction effect exist in these coordination polymers. Luminescent properties of the lanthanide-based MOFs (metal-organic frameworks) have been measured at room temperature, which reveal that they presenting ionselective characters toward certain metals, such as $Mg^{2+}$, $Cd^{2+}$ and $Pb^{2+}$ ions.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1579-1582
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• 2009

The reaction rates of 4-X-2,6-dinitrochlorobenzenes (X = $NO_2,\;CN,\;CF_3$) with Y-substituted pyridines (Y = 3-$OCH_3,\;H,\;3-CH_3,\;4-CH_3$) in methanol-acetonitrile mixtures were measured by conductometry at 25 ${^{\circ}C}$. It was observed that the rate constant increased in the order of X = 4-$NO_2\;>\;4-CN\;>\;4-CF_3$ and the rate constant also increased in the order of Y = 4-$CH_3\;>\;3-CH_3\;>\;H\;>\;3-OCH_3$. When the solvent composition was varied, the rate constant increased in order of MeCN > 50% MeOH > MeOH. The electrophilic catalysis by methanol may be ascribed to the formation of hydrogen bonds between alcoholic hydrogen and nitrogen of pyridines in ground state. Based on the transition parameters, ${\rho}_S,\;{\rho}_N,\;{\beta}_Y,\;{\rho}_{XY}$ and solvent effects, the reaction seems to proceed via $S_N$Ar-Ad.E mechanism. We also estimated the isokinetic solvent mixtures (${\rho}_{XY}$ = 0) based on cross-interaction constants, where the substituent effects of the substrate and nucleophile are compensated.