• Bulletin of the Korean Chemical Society
• /
• 제10권3호
• /
• pp.254-258
• /
• 1989

Adsorption of 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, and 1,6-hexanedithiol on silver surface has been investigated by surface-enhanced Raman spectroscopy. It has been found that the conformations of the adsorbates were mainly affected by steric interaction of the adsorbates with the surface. As the alkyl chain length separating the thiol groups increased, surface stacking efficiency became increasingly important in determining conformation of the adsorbate on the surface.

• 대한화학회지
• /
• 제34권5호
• /
• pp.389-395
• /
• 1990

칼륨 이온 치환 제올라이트 L과 C$_1$-C$_5$ 알칸 및 벤젠의 상호작용 퍼텐셜 에너지를 원자-원자 근사를 적용시켜서 계산하였다. 퍼텐셜 에너지 계산에 사용된 벤젠의 구성 원자 전하는 칼륨 이온과 벤젠 사이의 실험적 엔탈피 값으로부터 구했다. 계산된 퍼텐셜 에너지를 기초로하여 흡착분자의 열역학적 특성(흡착분자의 퍼텐셜 지도와 매우 낮은 피복률에서의 등량흡착열 및 내부에너지 변화량)을 계산하였다. C$_1$-C$_5$ 알칸의 계산된 등량흡착열은 실험데이타와 잘 일치하였지만, 벤젠의 계산값은 실험 값보다 조금 크게 나타났다.

• 상하수도학회지
• /
• 제28권2호
• /
• pp.235-248
• /
• 2014

The widespread occurrence of dissolved endocrine disrupting compounds(EDCs) and pharmaceutical active compounds(PhACs) in water sources is of concern due to their adverse effects. To remove these chemicals, adsorption of EDCs/PhACs on granular activated carbon(GAC) was investigated, and bisphenol A, carbamazepine, diclofenac, ibuprofen, and sulfamethoxazole were selected as commonly occurring EDCs/PhACs in the aquatic environment. Various adsorption isotherms were applied to evaluate compatability with each adsorption in the condition of single-solute. Removal difference between individual and competitive adsorption were investigated from the physicochemical properties of each adsorbate. Hydrophobicity interaction was the main adsorption mechanism in the single-solute adsorption with order of maximum adsorption capacity as bisphenol A > carbamazepine > sulfamethoxazole > diclofenac > ibuprofen, while both hydrophobicity and molecular size play significant roles in competitive adsorption. Adsorption kinetic was also controled by hydrophobicity of each adsorbate resulting in higher hydrophobicity allowed faster adsorption on available adsorption site on GAC. EDCs/PhACs adsorption on GAC was determined as an endothermic reaction resulting in better adsorption at higher temperature ($40^{\circ}C$) than lower temperature ($10^{\circ}C$).

• 자원리싸이클링
• /
• 제17권2호
• /
• pp.63-69
• /
• 2008

폐알칼리망간전지 분말에 대한 $Ni^{2+}$의 흡착 거동을 살펴보기 위하여 흡착제의 양, 홉착질의 초기농도 및 반응온도를 변화시켜 가며 그 특성을 조사하였다. $Ni^{2+}$의 흡착반응은 유사이차반응속도를 잘 따르는 것을 알 수 있었으며 $Ni^{2+}$의 초기농도가 증가함에 따라 유사이차반응속도상수($k_2$)는 감소하는 것으로 나타났다. 흡착평형을 표현하는데 널리 이용되는 Langmuir와 Freundlich 흡착 모델에 평형흡착 결과를 적용하였으며 Freundlich isotherm모델에 적합한 것으로 나타났다. 반응온도가 증가함에 따라 평형흡착량이 증가하여 흡착반응은 흡열반응의 양상을 보였으며 온도의 변화에 대한 실험결과로부터 ${\Delta}H^{\circ},\;{\Delta}G^{\circ}$ 그리고 ${\Delta}S^{\circ}$ 열역학적 변수를 도출하였다.

• 대한환경공학회지
• /
• 제33권8호
• /
• pp.606-616
• /
• 2011

본 연구는 흡착제의 흡착특성을 이해하는데 이용되는 각종 흡착모델의 적용성을 평가하는데 목적이 있다. 이를 위해 상용의 음이온교환수지(PA-308)를 이용하여 $NO_3^-$에 대한 흡착특성을 회분식 실험을 통해 조사하였다. 흡착등온과 흡착속도 실험결과는 일반적으로 널리 이용되고 있는 다양한 흡착등온식과 반응속도식을 통해 모델화하였다. 흡착평형실험은 흡착등온식을 적용하는데 있어 실험조건이 미치는 영향을 확인하기 위해 흡착제의 투여량을 일정한 값으로 고정하고 흡착질의 농도변화에 따른 조건과 흡착질의 농도를 일정한 값으로 고정하고 흡착제의 투여량 변화에 따른 조건으로 나누어 수행하였다. 흡착질의 농도를 변화시키는 조건에서의 흡착평형은 Langmuir와 Freundlich 흡착등온식을 결합한 형태의 Sips 흡착등온식과 Redlich-Perterson 흡착등온식에 의해 수식화가 가능하였다. 한편, 흡착제의 무게를 변화시키는 조건에서의 흡착평형은 단층 흡착, 균일표면을 가정하는 Langmuir 흡착등온식과 잘 일치하는 경향을 보였다. 이상의 결과는 $NO_3^-$에 대한 음이온교환수지의 흡착 메커니즘이 흡착실험 조건에 의해 달라질 수 있음을 시사한다.

• 한국자기공명학회논문지
• /
• 제9권1호
• /
• pp.1-20
• /
• 2005

Vanadium-incorporated aluminophophate molecular sieve VH-SAPO-11 has been studied by electron spin resonanace (ESR) and electron spin echo modulation (ESEM) spectroscopies to determine the vanadium locatin and interaction with various adsorbate molecules. As-synthsized VH-SAPO-11 contains only vanady1 species with distored octahral coordination. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. Species A is suggested as a VO$(H_2O)_2^{2+$} complex coordinate to three framwork oxygen bonded to aluminum. When calcined, hydrate VH-SAPO-11 is dehydrated at elevated temperature, species A loses it water ligands and transforms to $VO^{2+}$ ions coordinated to three framework oxygens (species B). Species B reduces its intensities significantly after treatment with $O_2$at high temperature, thus suggesting oxidation of $v^{4+}$to $v^{5+}$. When dehydrated VH-SAPO-11 contacts with $D_2O$ at room temperature, the ESR signal of species A is observed. This species assumed as a $VO(O_f)_3(D_2O)_2$, by considering 3 framework oxygens. Adsorption of deuterated methanol on dehydrated VH-SAPO-11 results in another new vanadium species D, which is identified as a $VO(CD_{3}OH)$ complex. When deuterated ethanol is adsorbed on dehydrated VH-SAPO-11, another new vanadium species E identified as a $VO(C_{2}H_{5}OD)^{2+}$, is observed. When deuterated propanol is adsorbed on dehydrated VH-SAPO-11, a new vanadium species F identified as a $VO(C_{3}H_{7}OD)$, is observed. Possible coordination geometries of these various complexes are discussed.

• 한국자기공명학회논문지
• /
• 제11권2호
• /
• pp.95-109
• /
• 2007

Vanadium-incorporated aluminophosphate microporous molecular sieve VH-SAPO-42 has been studied by electron spin resonance(ESR) and electron spin-echo modulation (ESEM) spectroscopies to determine the vanadium location and interaction with various adsorbate molecules. The results are interpreted in terms of V(IV) ion location and coordination geometry. Assynthesized VH-SAPO-42 contains only vanadyl species with distorted octahedral or trigonal bipyramidal coordination. Vanadium incorporated into H-SAPO-42 occupied extra-framework site. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. Species A is identified as a $VO(H_2O)_2^{2+}$ complex coordinated to three framework oxygen atoms bonded to aluminum. When hydrated VH-SAPO-42 is dehydrated at elevated temperature by calcination, species A loses its water ligand and transforms to $VO^{2+}$ ions coordinated to three framework oxygens (species B). Species B reduces its intensities significantly after treatment with $O_2$ at high temperature, thus suggesting oxidation of $V^{4+}$ to $V^{5+}$. When dehydrated VH-SAPO-42 makes contact with $D_2O$ at room temperature, the ESR signal of species A is regained. The species is assumed as a $VO(O_f)_3(D_2O)_2$ by considering three framework oxygens. Adsorption of deuterated methanol on dehydrated VH-SAPO-42 results in another new vanadium species D, which is identified as a $VO(CD_3OH)_2$ complex. When deuterated ethylene is adsorbed on dehydrated VH-SAPO-42, another new vanadium species E identified as a $VO(C_2D_4)^{2+}$, is observed. Possible coordination geometries of these various complexes are discussed.

• Bulletin of the Korean Chemical Society
• /
• 제29권2호
• /
• pp.438-444
• /
• 2008

A self-assembled monolayer of 2,2'-bipyridine (22BPY) molecules on Au(111) underwent a structural phase transition when the polarity of a bias voltage was switched in scanning tunneling microscopy (STM) experiments. The nature of two bright spots representing each 22BPY molecule on Au(111) in the high-resolution STM images was identified by calculating the partial density plots for a monolayer of 22BPY molecules adsorbed on Au(111) using tight-binding electronic structure calculations. The stacking pattern of the chains of 22BPY molecules on Au(111) was explained by examining the intermolecular interactions between the 22BPY molecules based on first principles electronic structure calculations for a 22BPY dimer, (22BPY)2. The structural instability of the 22BPY molecule arrangement caused by a change in the bias voltage switch was investigated by estimating the adsorbate-surface interaction energy using a point-charge approximation for Au(111).

• 한국자기공명학회논문지
• /
• 제9권2호
• /
• pp.138-154
• /
• 2005

Vanadium-incorporated aluminophosphate molecular sieve $VO^{2+}-SAPO-5$ was studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies to determine the vanadium structure and interaction with various adsorbate molecules. It was found that the main species at low concentration of vanadium is a monomeric vanadium units in square pyramidal or distorted octahedral coordination, both in oxidation state (IV) for the calcined hydrated material and in oxidation state (V) for the calcined material. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. It is suggested as a $VO(H_2O)_3^{2+}$ complex coordinated to two framework oxygen bonded aluminum. When calcined, hydrated $VO^{2+}-}SAPO-5$ is dehydrated at elevated temperature, a species loses its water ligands and transforms to $VO^{2+}$ ions coordinated to two framework oxygens (species B). Species B reduces its intensity, significantly after treatment with $O_2\;at\;600^{\circ}C$ for 5 h, thus suggesting oxidation of $V^{4+}\;to\;V^{5+}$. When dehydrated $VO^{2+}-SAPO-5$ contacts with $D_2O$ at room temperature, the EPR signal of species A is observed. Thus species assumed as a $VO^{2+}(O_f)_2(D_2O)_3$, by considering two framework oxygens. Adsorption of deuterated ethanol, propanol on dehydrated $VO^{2+}_{-}SAPO-5$ result in another new vanadium species E and F, respectively, which are identified as a $VO^{2+}-(CH_3CH_2OD)_3,\;VO^{2+}-(CH_3CH_2CH_2OD)_2$ complex. When deuterated benzene is adsorbed on dehydrated $VO^{2+}-SAPO-5$, another new vanadium species G, identified as a $VO^{2+}-(C_6D_6)$ is observed. Possible coordination geometries of these various complexes are discussed.

• 대한환경공학회지
• /
• 제29권9호
• /
• pp.1027-1034
• /
• 2007

본 연구에서는 탄화수소의 저온 화학증착 방법을 이용하여 흡착제인 pitch계 활성탄소섬유의 미세기공 또는 기공 입구의 크기를 조절한 다음 $CO_2$와 $CH_4$의 혼합 기체로 부터 $CO_2$ 또는 $CH_4$를 선택적으로 흡착 분리하는 기술에 대하여 고찰하였다. 기공 입구 크기는 조절하고자 하는 크기를 가지는 기체 분자를 흡착시키고 벤젠 또는 나프탈렌과 같은 덮개분자를 이용하여 기공의 입구를 막은 후 흡착된 기체분자를 서서히 탈착시키면서 덮개분자의 열리는 정도를 조절하였다. 기공 입구의 크기를 조절하는 실험에서 $CO_2$ 흡착 후 벤젠을 덮개분자로 하였을 때 $CO_2$가 탈착하는 온도와 벤젠이 휘발되는 온도의 차이가 크지 않아 $CO_2$와 함께 덮개분자인 벤젠도 휘발됨으로써 기공의 입구 조절이 불가능하게 되었다. 나프탈렌을 덮개분자로 사용한 실험에서 시료의 표면적은 753 $m^2/g$에서 0.7 $m^2/g$까지 줄어들어 거의 모든 기공 표면이 덮이는 것을 확인하였다. 나프탈렌은 ACF(활성탄소섬유) 무게의 약 15 wt% 정도 흡착이 가능하며, $100^{\circ}C$ 이하의 온도에서 쉽게 탈착되지 않았다. 나프탈렌으로 처리된 OG-7A 활성탄소섬유에서 $CO_2$와 $CH_4$가 50:50으로 혼합된 가스를 흡착시켰을 때 흡착압력이 증가할수록 $CO_2$의 흡착량은 증가한 반면, $CH_4$의 흡착량은 큰 변화 없이 일정하여 흡착압력이 높을수록 ACF 표면에서 화합물을 형성하는 $CO_2$의 양이 증가하는 것으로 파악되었다. 전체압력 0.4 atm에서 흡착된 $CO_2$는 동일한 진공에서 가장 많이 탈착되었고 $CH_4$는 가장 낮은 탈착량을 보여 고순도의 $CH_4$를 얻을 수 있음을 보였다.