• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.718-722
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• 2012

$H_2S$ adsorption characteristics of adsorbent made by sewage sludge were investigated. For analyses of the manufactured adsorbent, various methods such as Iodine adsorptivity, scanning electron microscope (SEM), and measurements of BET surface area and pore volume were adopted. As the major adsorption characteristic, breakthrough curve was measured by using a continuous fixed bed adsorption column for operating variables such as adsorption temperature ($25{\sim}45^{\circ}C$), aspect ratio (L/D)(3~9), gas flow rate (0.1~2.0 liter/min) and $H_2S$ gas concentration (50~200 ppm). The experimental result showed that the carbonization and activation of sewage sludge are very important for the improvement in $H_2S$ adsorption capacity.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.141-141
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• 1999

전기화학과 초고진공(ultra-high vacuum, UHV) 분광법을 이용하여 고체/액체의 계면에서 일어나는 현상을 분자단위에서 이해하고 조절하기 위한 연구를 수행하였다. 이들 중 전기화학으로 형성된 구리 및 은 금속(sub)monlayer 박막을 그 예로 선택하여 소개한다. 초박막 금속의 흡착량은 cyclic voltammogram과 새로 개발된 Auger electron spectroscopy (AES) 정량법을 통해 얻어졌고, 이 값들은 low energy electron diffraction (LEED) 및 in-situ atomic force microscopy (AFM)법을 이용한 구조 분석결과와 비교되어졌다. 또한 화학상태를 확인하기 위하여 core-level electron energyy loss spectroscopy (CEELS)를 사용하였다. 먼저 황산 전해질에서 금(111) 단결정 전극상에 전기화학적으로 형성된 굴의 계면특성을 조사하였다. 특정 전위값에서 2/3 ML의 구리와 1/3 ML의 음이온이 상호 흡착하여 ({{{{ SQRT { 3} }}$\times${{{{ SQRT { 3} }}) 격자 구조를 보였고, 전위값이 커지거나 줄어들면, 이 구조가 사라지는 현상이 관찰되었다. 즉 이 ({{{{ SQRT { 3} }}}}$\times${{{{ SQRT { 3} }}}}) 흡착구조는 첫 번째 UPD underpotential deposition) 피크에 특이하게 관련되어 있음을 알 수 있었다. 금속 초박막 형성에 미치는 음이온의 영향을 좀 더 확인하기 위해 초박막 은이 증착된 금 단결정 전극상의 황산 음이온에 관하여 연구하였다. 은의 증착이 일어날 수 없는 양전위값 영역에서 ({{{{ SQRT { 3} }}}}$\times${{{{ SQRT { 3} }}}})의 규칙적인 음이온의 구조를 보였다. 그리고 은의 장착은 세척 과정과 용액의 농도에 따라 p(3$\times$3)과 p(5$\times$5)의 규칙적인 두가지 구조를 가졌다. in-situ AFM에서는 p(3$\times$3)의 은 증착 구조만 나타났고, 음 전위값으로 옮겨가면 p(1$\times$1) 구조로 바뀌었다. ex-situ 초고진공 결과와 이 AFM의 in-situ 결과를 상호 비교 논의할 것이다. 음이온의 흡착이 없는 묽은 플로르산(HF) 전해질에서 은은 전위값을 음전위 쪽으로 이동해 감에 따라 p(3$\times$3), p(5$\times$5), (5$\times$5), (6$\times$6), 그리고 (1$\times$1)의 연속적 구조 변화를 보였다. 이 다양한 구조들을 AES로부터 얻어진 표면 흡착량과 연결시켰더니 정량적으로 잘 일치되는 결과를 보였다. 전기화학적인 증착에서는 기존의 진공 증착과 비교할 때 음이온의 공흡착이 금속 초박막 형성 메카니즘에 큰 영향을 미침을 알 수 있었다. 또한 은의 전기화학적 다층박막 성장은 MSM (monolayer-simultaneous-multilayer) 메카니즘을 따름을 확인하였다. 마지막으로 구조 및 양이 규칙적으로 조절되는 전극의 응용가능성이 간단히 논의될 것이다.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.445-451
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• 2008

In order to regenerate the activated carbon polluted by volatile organic compounds (VOCs) using microwave, adsorption and desorption characteristics of benzene over activated carbon (AC) coated with insulating materials were investigated. Physical characteristics of activated carbon and insulator-coated ACs were investigated by means of $N_2$ gas adsorption and scanning electron microscopy (SEM). The amount of VOC adsorbed showed a positive relationship with the specific surface area of the ACs, and spark discharge over insulator-coated ACs did not occur. Potassium silicate (PS) was the best binder for coating of insulating materials on AC. Amount of benzene desorbed by microwave irradiation was dependent on output power of microwave. Nearly same performance was obtained even though the adsorption-desorption operation under microwave irradiation was repeated 5 times. Finally, it was known that the microwave heating was a very effective mean for regenerating the polluted AC.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.337-343
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• 2007

The reforming catalyst and the electrodes in fuel cells can be poisoned by the organic sulfur compound which is added as an odorant for checking out the leakage of natural gas, and that makes a big problem of system degradation. In this study, various adsorbents, such as silica, ${\gamma}$-alumina, activated carbon, HZSM-5, Ultra-stable Y zeolite (USY), and beta zeolite (BEA), were utilized to remove tetra-hydrothiophene (THT) and tert-butylmercaptan (TBM), and to confirm the performance in the adsorption of those odorants by using a continuous adsorptive bed. The effects of Si/Al ratio of zeolites, adsorption temperature and the type of balance gas (methane or He) on the adsorption performance in the packed bed have been investigated. In addition, the competitive adsorption between TBM and THT on the adsorbents was also estimated. The result shows that H-type BEA zeolite exhibited the highest adsorption capacity for TBM and THT odorant, and the higher amount of THT was removed adsorptively on the same adsorbent than TBM. The physical and chemical adsorption of those compounds on acid sites of zeolite were confirmed by temperature programmed desorption (TPD) and infrared spectrum (IR) analyses.

• Membrane Journal
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• v.14 no.1
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• pp.75-84
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• 2004

In this study, we present a noble study far membrane transport models using chlorine resistance of polyamide RO membranes. Membrane transport mechanism is investigated by the comparison of membrane permeation performance under the continuous and Intermittent operation modes with mixed feed solution containing NaOCl and NaCl. Analysis of permeation performance indicates that solution-diffusion model and preferential adsorption-capillary flow model are relatively efficient according to operation mode. Under the continuous flow state, mass transfer depends on preferential adsorption-capillary flow model rather than solution-diffusion model. On the other hand, it prefers solution-diffusion model to preferential adsorption-capillary flow model under the stationary state. SEM images of NaOCl treated membrane surfaces strongly support these conclusions. These surface images reveal that NaOCl treated membrane in continuous operation mode exhibits ridge and valley structure in some fraction of the surface area, whereas that in intermittent operation mode shows surface degradation entirely.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.4
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• pp.375-382
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• 1999

In order to investigate the contamination characteristics of the heavy metals in the mine tailings of abandoned gold mine and its surrounding agricultural soils, a sequential extraction procedure of increasing reactivity in the dissolution processes of the heavy metals(Cd, Cu, and Pb) which were associated with solid and/or solution phase in soils was attempted to partition into six particulate fractions : exchangeable, bound to carbonate, bound to Fe-Mn oxides, bound to organic matter, residual, and soluble. Among indigenous heavy metals in the mine tailings, Pb was the most abundant and Cu and Cd were followed by. Fractionation result of Pb obtained from the triplicate samples of the mine tailings were in the order of Fe-Mn oxide> Carbonate> Residual> Organic> Exchangeable> Soluble, while Wolgok series were Exchangeable > Fe-Mn oxide > Carbonate> Organic> Residual> Soluable. However the other heavy metals studied were not followed this trend. The fractionation results of mine tailing and agricultural soils demonstrated that different geochemical fractions were operationally defined by an extraction sequence that generally followed the order of decreasing solubility. Therefore potential mobility and bioavailability of heavy metals as toxic pollution sources can be evaluated when studying the pollution levels of heavy metals in soils.

• Clean Technology
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• v.28 no.3
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• pp.249-257
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• 2022

The adsorption equilibria of nitrogen on a region of nanoporous carbonaceous adsorbent with local molecular orientation (LMO) were calculated by grand canonical Monte Carlo simulation at 77.16 K. Regions of LMO of identical size were arranged on a regular lattice with uniform spacing. Microporosity was predominately introduced to the model by removing successive out-of-plane domains from the regions of LMO and tilting pores were generated by tilting the basic structure units. This pore structure is a more realistic model than slit-shaped pores for studying adsorption in nanoporous carbon adsorbents. Their porosities, surface areas, and pore size distributions according to constrained nonlinear optimization were also reported. The adsorption in slit shaped pores was also reported for reference. In the slit shaped pores, a clear hysteresis loop was observed in pores of greater than 5 times the nitrogen molecule size, and in capillary condensation and reverse condensation, evaporation occurred immediately at one pressure. In the LMO pore model, three series of local condensations at the basal slip plane, armchair slip plane and interconnected channel were observed during adsorption at pore sizes greater than about 6 times the nitrogen molecular size. In the hysteresis loop, on the other hand, evaporation occurred at one or two pressures during desorption.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.2
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• pp.107-112
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• 1996

To clarify the mechanism of silica adsorption to soil, kinetic study using continuous stirred-flow method was conducted with the Luisiana soil at three pH levels (pH 5.0, 6.5, and 8.0). Silica adsorption increased continuously without showing the maximum adsorption for long enough experimental time. Kinetic curve of silica adsorption could be divided into two stage processes. The first stage process was fitted well to the following equation with highly significant correlation coefficient : $$R_{ad}=K_a*(Q_{OH}^S)^n$$ where, $R_{ad}$ is silica adsorption rate($Si\;{\mu}mal/min$). $Q_{OH}^S$ is the negative charge sites on the soil surface created by alkali titration, and $K_a$ and n are constants. The "n" value of the first stage process was 1.1. This value indicates that the silica adsorption is accomplished by the monodendate ligand bonding. The second stage process was fitted well to the following equation : $$R_{ad}=K_b*(pH)$$ where, $K_b$ is a constant. The equation indicates that the silica adsorption is not proportional to the $OH^-$ ion concentration. Rather, the increasing pattern of silica adsorption rate with the increase of $OH^-$ ion concentration would decrease exponentially.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.1
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• pp.60-65
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• 2000

Biosorptions of Cr and Pb were evaluated for 23 species of marine algae collected from a Korean coast. Among a variety of species for biosorbent potential, Sargassum species showed higher uptake capacity for Cr and Pb. An adsorption equilibrium was reached in about 1 hr for Cr and 30 min for Pb. The maximum uptake capacity was136.0 mg Cr/g biomass and 232.5 mg Pb/g biomass, respectively. In Pb biosorption in the column packed with Sargassum tbunbertii, 300 and 200 bed Tolumes at the concentration of 50 mg/L in feed solution were processed at the column residence time of 5 and 10 min before the column breakthrough point occurred. The elutions with 0.1 M HCl solution were more than $95{\%}$. The high efficiency of continous biesorntion and elution (3 cycles) indicated that Sargassum thunbergii was an effective biosorbent for Pb recovery.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.2
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• pp.133-138
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• 2006

Chemical wastes containing small amounts of uranium can not be disposed of them after treatment as an industrial waste, because the uranium concentration in the final dry cake exceeds the exemption level. Especially for the removal of uranium in this study, the method for immobilizing Diphosil powder within alginate beads is adopted to make a bead form from a powdered resin. Sodium alginate bead itself showed a capability to uptake uranium to above 60%, but the value was decreased to below 30% after equilibrium. The adsorption rate of uranium increased with the increasing content of Diphosil in the sodium alginate bead. Diphosil resin itself showed very fast uptake of uranium from early stages, and then the rates were leveled off. Diphosil bead showed an improved capability to uptake uranium considering the pure Diphosil content in the composite bead, and provide a considerable potential for further applications of a continuous process by using Diphosil as a bead form.