• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.139-139
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• 2000

We have investigated the adsorption and reaction of Cu(hfac)(vtms) on Cu(111) surface using TPD. The recombinative desorption of Cu(hfac)(vtms) reversibly occurs between 240 and 340K. The remaining Cu(hfac) after the desorption of vtms preferentially undergo the desorption between 330 and 370K as intact Cu(hfac) than the disproportionation reaction. The disprportionation reaction between adsorbed Cu(hfac) was observed to occur between 420 and 520K with an activation energy of 34~37 kcal/mol. the geometries and adsorption sites of Cu(hfac) have been also calculated by means of extended H ckel method. It is found that standing Cu(hfac) is more stable than lying-down Cu(hfac) on the Cu(111) surface and the Cu(hfac) molecule prefers to adsorb on the hollow site over the top or bridge sites. We also have investigated the surface modification effect by preadsorbed I and Na atoms on the reaction Cu(hfac)(vtms).

• Bulletin of the Korean Chemical Society
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• v.16 no.2
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• pp.89-95
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• 1995

The adsorption of methanethiol and benzenethiol on Ag(111) and Ag(100) surfaces is studied respectively, employing ASED (Atom Superposition and Electron Delocalization) method. Metal surfaces are modelled by 3-layer clusters. The corresponding thiolate anions are taken as adsorbates. The highly coordinated binding sites are most favored for both surfaces. The tilted angles of C-S axis from the surface normal are nearly zero. There's Charge transfer from adsorbate to substrate and the stretching frequency of C-S bond upon adsorption is blue-shifted from its gas phase counterpart, and its amount is the smallest at most highly coordinated site. FMO (Fragment Molecular Orbital) analysis of the system give the explanation for these results.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.636-645
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• 2022

In this study, we investigated the adsorption characteristics of methyl orange (MO), an anionic dye, on ginkgo shell-based activated carbon (AC). For this purpose, ACs (GS-1, GS-2, and GS-4) with different textural properties were prepared using ginkgo shells and potassium hydroxide (KOH), a representative chemical activating agent. The correlation between the textural characteristics of AC prepared and the mixing ratio of KOH was investigated using nitrogen adsorption/desorption isotherms. The MO adsorption equilibrium experiment on the prepared ACs was conducted under different pH (pH 3~11) and temperature (298~318 K) conditions, and the results were investigated by Langmuir, Freundlich, Sips and temperature-dependent Sips equations. The feasibility of the MO adsorption treatment process of the prepared AC was also investigated using the dimensionless Langmuir separation factor. The heterogeneous adsorption properties of MO for the prepared AC examined using the adsorption energy distribution function (AED) were closely related to the system temperature and textural characteristics of AC. The kinetic results of the batch adsorption performed at different temperatures can be satisfactorily explained by the homogeneous surface diffusion model (HSDM), which takes into account the external mass transfer, intraparticle diffusion, and active site adsorption. The relationship between the activation energy value obtained by the Arrhenius plot and the adsorption energy distribution function value was also investigated. In addition, the adsorption process mechanism of MO on the prepared AC was evaluated using Biot number.

• Korean Journal of Materials Research
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• v.26 no.6
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• pp.298-305
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• 2016

In this work, recent progress on graphene/metal oxide composites as advanced materials for $HgCl_2$ and $CO_2$ capture was investigated. Density Functional Theory calculations were used to understand the effects of temperature on the adsorption ability of $HgCl_2$ and water vapor on $CO_2$ adsorption on CaO (001) with reinforced carbon-based nanostructures using B3LYP functional. Understanding the mechanism by which mercury and $CO_2$ adsorb on graphene/CaO (g-CaO) is crucial to the design and fabrication of effective capture technologies. The results obtained from the optimized geometries and frequencies of the proposed cluster site structures predicted that with respect to molecular binding the system possesses unusually large $HgCl_2$ ($0.1-0.4HgCl_2g/g$ sorbent) and $CO_2$ ($0.2-0.6CO_2g/g$ sorbent) uptake capacities. The $HgCl_2$ and $CO_2$ were found to be stable on the surface as a result of the topology and a strong interaction with the g-CaO system; these results strongly suggest the potential of CaO-doped carbon materials for $HgCl_2$ and $CO_2$ capture applications, the functional gives reliable answers compared to available experimental data.

• Journal of Environmental Science International
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• v.15 no.6
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• pp.579-586
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• 2006

The purposes of this paper were to monitor the temperature rising courses and spark discharge of the modified granular activated carbon (GAC) by microwave (MW) irradiation and to evaluate absorption of benzene. The GAC coated on $SiO_2$, boron, talc, ferrite was named as the modified GAC. Thermal and spark discharge measurement of virgin GAC and modifed GAC has been carried out using a MW device operating at 2450 MHz under various energy conditions. The results of this paper as follows. First, the modified GAC is more efficient than the virgin GAC in temperature control. Temperature gradient of the modified GAC is more lower than that of virgin GAC. The temperature gradient of GAC was observed in the following order : virgin GAC, Mn-Zn ferrite/GAC, Ni-Zn ferrite,/GAC, $SiO_2/GAC$, Boron/GAC, Talc/GAC. Second, the spark discharge of the modified GAC was diminished, compared with that of virgin GAC. Because of its excellent electrical insulating properties, the coating material prevents the spark discharge. Finally, the benzene adsorption capacity of the modified GAC decreased due to diminishing of adsorption site by the coating material. Considering the temperature gradient and spark discharge of GAC, the GAC coated $SiO_2$ would be appropriate absorbent under irradiation of MW.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.160.1-160.1
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• 2014

Using a density functional theory calculation including van der Waals (vdW) corrections, we report that $H_2$ adsorption in a cubic-crystalline microporous metal-organic framework (MOF-5) leads to volume shrinkage, which is in contrast to the intuition that gas adsorption in a confined system (e.g., pores in a material) increases the internal pressure and then leads to volumetric expansion. This extraordinary phenomenon is closely related to the vdW interactions between MOF and $H_2$ along with the $H_2$-$H_2$ interaction, rather than the Madelung-type electrostatic interaction. At low temperatures, $H_2$ molecules adsorbed in the MOF-5 form highly symmetrical interlinked nanocages that change from a cube-like shape to a sphere-like shape with $H_2$ loading, helping to exert centrosymmetric forces and hydrostatic (volumetric) stresses from the collection of dispersive interactions. The generated internal negative stress is sufficient to overcome the stiffness of the MOF-5 which is a soft material with a low bulk modulus (15.54 GPa).

• Journal of the Mineralogical Society of Korea
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• v.11 no.2
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• pp.106-116
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• 1998

The adsorption of Cs-137 and Sr-90 onto kaolinite in prescence of major groundwater cations (Ca2+, K+, Na+) with different concentrations was simulated by using triple-layer surface complexation model (TL-SCM). The site density (8.73 sites/nm2) of kaolinite used for TL-SCM was calculated from it's CEC and specific surface area. TL-SCM modeling results indicate that concentrations dependence on 137Cs and 90Sr adsorption onto kaolinite as a function of pH is best modeled as an outer-sphere surface reaction. This suggests that Cs+ and Sr2+ are adsorbed at the $\beta$-layer in kaolinite-water interface where the electrolytes, Nacl, KCl and CaCl2, bind. However, TL-SCM results on Sr adsorption show a discrepancy between batch data and fitting data in alkaline condition. This may be due to precipitation of SrCO3 and complexation such as SrOH+. Intrinsic reaction constants of ions obtained from model fit are as follows: Kintcs=10-2.10, KintSr=10-2.30, KintK=10-2.80, KintCa=10-3.10 and KintNa=10-3.32. The results are in the agreement with competition order among groundwater ions (K+>Ca2+>Na+) and sorption reference of nuclides (Cs-137>Sr-90) at kaolinite-water interface showed in batch test.

• Journal of the Mineralogical Society of Korea
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• v.20 no.4
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• pp.327-337
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• 2007

Mineral compositions were determined using quantitative X-ray diffraction analysis on the three kinds of Youngdong illite consisting of white, yellow and refined yellow samples. Mean particle size and their size distribution patterns were measured by laser particle size analyzer. The characteristics of phosphate adsorption on illite were studied through batch adsorption experiments. The white illite has less illite content, but is finer than that of yellow. The refined yellow illite has more illite content and finer particle size compared with those of raw yellow illite. The adsorption rate of phosphate generally increases when the mass of illite increases, whereas adsorption quantity decreases with ascending pH. The phosphate adsorption usually increases with ascending illite content or descending particle size. Although the white illite has lower illite content than the yellow, the former has higher phosphate adsorption quantity than the latter. This can be ascribed to the fine particle size, high interlayer charge, and low substitution in tetrahedral site of white illite. The adsorption isotherms of white illite are well fitted with the Langmuir equation, however those of yellow one are better with Freundlich equation.

• Korean Journal of Materials Research
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• v.1 no.4
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• pp.184-190
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• 1991

Oxygen chemisorption on single crystal ZrC(111) surface was studied by high-resolution electron energy loss and ultraviolet photoelectron spectroscopy. At a low amount of oxygen exposure, adsorbed oxygen atoms construct $(\sqrt{3}{\times}\sqrt{3})R30^{\circ}$ structure. On the other hand, oxygen adsorption changes into $1{\times}1$ structure as the amount of oxygen exposure increases. The adsorbed oxygen atoms show smaller vertical distance from the Zr topmost layer in the $1{\times}1$ structure than in the $(\sqrt{3}{\times}\sqrt{3})R30^{\circ}$ structure and approach to the bridge site rather than 3-fold hollow site. The two different oxygen adsorption behavior comes from the two different surface stales of the clean ZrC(111) surface.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.3
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• pp.180-191
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• 2016

Optimizing energy usage for maximum efficiency is an essential goal for manufacturing plants in every industrial manufacturing sector. The generation and distribution of purifying compressed air is a large expense incurred in practically all manufacturing processes. Not only is the generation and treatment expensive equipment of compressed air, but frequent maintenance and effective operation is also required. As a plant's compressed air system is often an integral part of the production process, it needs to be reliable, efficient, and easy to be maintain. In this paper, we study to find operating method to save energy from the adsorption dryer in the process of purifying compressed air, which is required for a clean room production site in "A" company. The compressed air passes through a pressure vessel with two "towers" filled with a material such as activated alumina, silica gel, molecular sieve or other desiccant material. This desiccant material attracts the water from the compressed air via adsorption. As the water clings to the desiccant, the desiccant particle becomes saturated. Therefore, Adsorption dryer is an extremely significant facility which removes the moisture in the air $70^{\circ}C$ below the dew point temperature while using a lot of energy. Also, the energy consumption of the adsorption dryer can be varied by various operating conditions (time, pressure, temperature, etc). Therefore, based on existing operating experiments, we have searched operating condition to maximize energy saving by changing operating conditions of the facility. However, due to a short experiment period (from September to October), further research will be focused on considering seasonality.