• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.653-660
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• 1996

For oxygen PSA process development, adsorbed amount of oxygen and nitrogen on various adsorbents were measured corresponding Langmuir isotherm parameters were measured. A reasonable adsorbent for oxygen process was selected based on the effective adsorbed amount. The PSA process consists of adsorption, desorption, pressurization, purging and pressure equilization steps. Adsorption pressure was about 2 atm and desorption pressure was between 120 torr to 400torr. Cycle time of 2-bed PSA process was 80 seconds and that of 3-bed oxygen PSA process was 180 seconds. In order to compare and analyze operation characteristics and economic feasibilities of 2-bed and 3-bed oxygen PSA processes, productivity, oxygen concentration and recovery were compared and the effect of purge and pressurization steps on the performance of PSA processes were analyzed. For the commercial scale oxygen PSA process, capital and electricity cost were estimated. In the range of $O_2$ production less than $700Nm^3/hr$, the 2-bed process is conformed more feasible in economic view point.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.840-846
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• 2016

Great amounts of solid radioactive waste (second waste) and waste solution are generated from the remediation of uranium-contaminated soil. To reduce these, we investigated washing with a less acidic solution and recycling the waste solution after removal of the dominant elements and uranium. Increasing the pH of the washing solution from 0.5 to 1.5 would be beneficial in terms of economics. A high content of calcium in the waste solution was precipitated by adding sulfuric acid. The second waste can be significantly reduced by using sorption and desorption techniques on ampholyte resin S-950 prior to the precipitation of uranium at pH 3.0.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.602-608
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• 2014

The sequence of bond overlap population of metal hydrogen binding is in Al-H > Fe-H > Zr-H > V-H. This results shows the binding energy of Al-H is the biggest in this metals (Al, Fe, Zr, and V) and hydrogen interaction. The Vanadium-hydrogen binding shows the weakest binding energy compared to other metals and it causes easy hydrogen desorption from the corresponding metals. The net charge of Al-H show the biggest value of 0.2248 and the severe localizations of electrons around aluminum and imply strongest covalent binding nature in these metals. This study is applicable to the purification of hydrogen in other bulk gas.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11b
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• pp.214-221
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• 2005

Spent ion-exchanged resin generated from various purification systems in CANDU reactor is causing concern due to a limited storage capacity and safe disposal. As a suggestion for a proper treatment technology for the spent ion-exchanged resin containing a high activity of C­14 radionuclide which would be classified as Class A and C wastes, a fundamental study for the development of C-14 removal technology from a spent resin was performed. The adsorption characteristics of the inactive $HCO_3^-$ ion and other ions in a stripping solution on IRN-150 mixed resin was evaluated and the removal technology of the $HCO_3^-$ ion adsorbed on IRN-150 by an alkaline stripping method was proposed.

• Bulletin of the Korean Chemical Society
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• v.11 no.4
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• pp.290-296
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• 1990

Ion-surface collision studies at low kinetic energies (1-100 eV) provide a unique opportunity for investigating reactions and collision dynamics at surfaces. A special ion optics system for generating an energy- and mass-selected ion beam of this energy is designed and constructed. An ultrahigh vacuum (UHV) reaction chamber, in which the ions generated from the beamline collide with a solid surface, is equipped with Auger electron spectroscopy (AES) and thermal desorption spectrometry (TDS) as in-situ surface analytical tools. The resulting beam from the system has the following characteristics : ion current of 5-50 nA, energy spread < 2eV, current stability within ${\pm}5%,$ and unit mass resolution below 20 amu. The performance of the instrument is illustrated with data representing the implantation behavior of $Ar^+$ into a graphite (0001) surface.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.622-628
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• 2010

In this study, Solid-phase microextraction (SPME) with GC/FID was studied as a possible alternative to liquid-liquid extraction for the analysis of BTEX and MTBE. Experimental parameters affecting the SPME process (such as kind of fibers, adsorption time, desorption time, volume ratio of sample to headspace, salt addition, and magnetic stirring) were optimized. Experimental parameters such as CAR/PDMS, adsorption time of 20 min, desorption time of 5 min at $250^{\circ}C$, headspace volume of 50 mL, sodium chloride (NaCl) concentration of 25% combined with magnetic stirring were selected in optimal experimental conditions for analysis of BTEX and MTBE. The general affinity of analytes to CAR/PDMS fiber was high in the order p-Xylene>Toluene>Ethylbenzene>MTBE>Benzene. The linearity of $R^2$ for BTEX and MTBE was from 0.970 to 0.999 when analyte concentration ranges from $30{\mu}g/L$ to $500{\mu}g/L$, respectively. The relative standard deviation (% RSD) were from 2.5% to 3.2% for concentration of $100{\mu}g/L$ (n=5), respectively. Finally, the limited of detection (LOD) observed in our study for BTEX and MTBE were from $7.5{\mu}g/L$ to $15{\mu}g/L$, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.4
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• pp.191-196
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• 1999

4-probe resistivity measurement technique was used to study hydrogen A-D(Absorption-Desorption)kinetics on Pd films(18 to 67nm thick) from 25 to $50^{\circ}C$, from 0 to 5 torr hydrogen pressure. Pd films were made on sapphire substrate by thermal evaporation technique under high vacuum at room temperature. Upto about 100 hydrogen A-D cyclings, no pulverization was observed, but film was detached partially from substrate. Forward reaction and backward reaction rate were analyzed separately. The activation energies of hydrogen A-D processes were obtained from the Arrhenius plot of the reaction rates. The activation energies of Pd films are not strongly dependent on the thickness of the film. But the activation energy of very thin film( l8nm thick) was smaller than the others.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.117-125
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• 2009

In order to utilize natural gas (NG), one of the clean energy sources in next-generation, as a fuel for vehicles, it is important to store natural gas with high density. To store NG by adsorption (ANG) at room temperature and at relatively low pressure(35~40 atm) is safe and economical compared with compressed NG and liquefied NG. However, so far no adsorbent is reported to have adsorption capacity suitable for commercial applications. Nanoporous materials including metal-organic frameworks can be potential adsorbents for ANG. In this review, physicochemical properties of adsorbents necessary for high adsorption capacity are summarized. Wide surface area, large micropore volume, suitable pore size and high density are necessary for high energy density. Moreover, low adsorption-desorption energy, rapid adsorption-desorption kinetics and high delivery are needed. Recently, various efforts have been reported to utilize nanoporous materials in ANG, and it is expected to develop a nanoporous material suitable for ANG.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.455-460
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• 2012

This work describes the hydriding chemical vapor synthesis (HCVS) of the $MgH_2$ in a hydrogen atmosphere and the product's hydriding-dehydridng properties. Mg powder was used as a starting material to synthesize $MgH_2$ and uniformly heated to a temperature of $600^{\circ}C$ for Mg vaporization. The effects of hydrogen pressure on the morphology and the composition of HCVS-$MgH_2$ were examined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is clearly seen that after the HCVS process, the particle size of synthesized $MgH_2$ was drastically reduced to the submicron or micrometer-scale and these showed different shapes (needle-like nanofibers and angulated plate) depending on the hydrogen pressure. It was found that after the HCVS process, the $H_2$ desorption temperature of HCVS-$MgH_2$ decreased from 380 to $410^{\circ}C$, and the minimum hydrogen desorption tempreature of HCVS-$MgH_2$ powder with needle-like shape can be obtained. In addition, the enhanced hydrogen storage performance for needle-like $MgH_2$ was achieved during subsequent hydriding-dehydriding cycles.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.171-178
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• 1988

The potential energy of adsorbate molecules in the main channel of $K^+$ ion exchanged zeolite L(K-L) was calculated. In K-L which adsorbs three molecules per unit cell, the interaction energies of $H_2O,\;NH_3,\;CH_3NH_2,\;(CH_3)_2NH,\;and\;(CH_3)_3N$ molecules with zeolite lattice are 61.11, 62.31, 65.68, 74.65, and 79.88kJ/mol, respectively. These values are less by 3.7∼12.6kJ/mol than $K^+$ ion affinities with adsorbing molecules. These results may be due to the facts that the electrostatic energies are reduced by the negative charge of the lattice oxygens. The distribution of adsorption sites of $NH_3$ and $CH_3NH_2$ in K-L was investigated by a technique of temperature programmed desorption. The experimental value of desorption energies of $NH_3$ and $CH_3NH_2$ on K-L are in good agreement with the theoritical values. It is concluded that the desorption of $NH_3$ and $CH_3NH_2$ on K-L is the first-order desorption with free readsorption.