• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1229-1230
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• 2006

Adsorption isotherms of hydrogen by step-by-step method are widely used. However, the relations between the equations of state and the accumulated errors produced by step-by-step method and the mechanical errors of pressure or temperature controller were not analyzed. Considering the influence of various errors on the equations of state, we could find out the factors and compare the performance of the equations of state.

• Textile Coloration and Finishing
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• v.12 no.6
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• pp.344-352
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• 2000

Two kinds of nylon 6 fabrics with different fiber denier, such as ultramicro fiber(UMF) nonwoven fabric(monodenier 0.05d) and regular fabric(monodenier 2.92d) are dyed with C.I. Acid Red 18(leveling type) and C.I. Acid Blue 113(milling type). Dyeing rates and adsorption isotherms are measured at $60^\circ{C}$, pH 5.0 and at liquor ratio of 1 : 250. To investigate the effect of fixing agents (Matexil FA-SNX, Monorex-RD and Tinofix-ECO) on UMF nylon 6 nonwoven fabric, dyeing is carried out at 3~10% owf with 1 : 2 metal-complex acid dyes, such as Kayalax Navy R(unsulphonated type), Lanasyn Blue S-BL(monosulphonated type) and Kayakalan Black BGL(disulphonated type). The dyeing rate of UMF nylon 6 is faster than that of regular nylon 6. From the results of absorption isotherms, the regular nylon 6 has higher saturation value of Acid Red 18 compared with UMF nylon 6, whereas UMF nylon 6 has higher saturation value of the acid Blue 113. From the absorption isotherms of both acid dyes, the regular nylon 6 has higher saturation value of Acid Red 18, whereas UMF nylon 6 has higher saturation value of the acid Blue 113. The wash fastnesses of UMF nylon 6 increases in the order of metal-complek dye containing nonsulphonated group > monosulphonated group>disulphonated group. Aftertreatment of UMF nylon 6 dyed with unsulponated and monosulphonated dyes improves wash fastness upto grade 1.5, where as that of UMF nylon 6 dyes with disulphonated dye does not improve wash fastness.

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.14-20
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• 2001

The Langmuir adsorption isotherms of the under-potentially deposited hydrogen (UPD H) and the over-potentially deposited hydrogen (OPD H) at the single crystal Pt(100)/0.5 M $H_2SO_4$ and 0.5 M LiOH aqueous electrolyte interfaces have been studied using the phase-shift method. The phase-shift profile $({-\varphi}\;vs.\;E)$ for the optimum intermediate frequency can be used as a useful method to estimate the Langmuir adsorption isotherm $(\theta\;vs.\;E)$ at the interfaces. The equilibrium constant (K) for the OPD H and the standard free energy $({\Delta}G_{ads})$ of the OPD H at the Pt(100)/0.5M $H_2SO_4$ aqueous electrolyte interface are $1.5\times10^{-4}$ and 21.8 kJ/mol, respectively. At the Pt(100)/0.5 LiOH aqueous electrolyte interface, K transits from 1.9(UPD H) to $6.8\times10^{-6}$(OPD H) depending on the cathode potential (E) and vice versa. Similarly, ${\Delta}G_{ads}$ transits -1.6 kJ/mol (UPD H) to 29.5 kJ/mol (OPD H) depending on E and vice versa. The transition of K and ${\Delta}G_{ads}$ is attributed to the two distinct adsorption sites of the UPD H and OPD H on the Pt(100) surface. The UPD H and the OPD H at the Pt(100) interfaces are the independent processes depending on the H adsorption sites rather than the sequential processes for the cathodic $H_2$ evolution reactions.

• Journal of Environmental Health Sciences
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• v.34 no.3
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• pp.240-246
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• 2008

The purpose of this study was to gain basic information on the characteristics of $CO_2$ adsorption in relation to $Na_2CO_3$, $K_2CO_3$, $Li_2CO_3$-impregnated activated carbon in a Fixed Bed Reactor. From the results of this study the following conclusions were made: $Na_2CO_3$, $K_2CO_3$, $Li_2CO_3$-impregnated activated carbon had a longer breakthrough time and more enhanced adsorption capacity than activated carbon alone. When tested with isothermal adsorption and tested for $CO_2$ adsorption the amount of $CO_2$ adsorbed varied with temperature, $CO_2$ inlet concentration, gas flow rate, aspect ratio, etc. Based on the results, when Langmuir, Freundlich and Dubinin-Polanyi adsorption isotherms were used for linear regression of isothermal adsorption data, Langmuir adsorption isotherm was the most suitable. And, the optimum condition for $Na_2CO_3$ and $K_2CO_3$ impregnated activated carbon make-up was 1N and $Li_2CO_3$ was 0.1N. It could be concluded that adsorption capacity was decreased with adsorption temperature and increased gas concentration. When the aspect ratio (L/D) was varied 0.5, 1.0 and 2.0, the significant drop of adsorption amount was observed below 1.0 and breakthrough time was shortened with gas flow rate.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.179-189
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• 2008

The performance of Lean NOx Trap (LNT) based on the catalysts of Pt/K/Ba/$\gamma-Al_2O_3$ with proprietary washcoat formulation is studied using a bench flow reactor system. To investigate the effect of temperature and gas hourly space velocity (GHSV) on the nitrogen oxides (NOx) trapping capacity as well as NOx breakthrough time and final ratio of $NO_2$ to NO of LNT, series of adsorption isotherms are carried out with simulated exhaust gases of the lean burn engines. Since typical operation of LNT requires periodic regeneration with a short rich excursion, where the stored or trapped NOx is released and subsequently reduced to $N_2$, the effect of the duration of lean and rich phase and type of reductants on the NOx conversion is investigated. NOx storage capacity and breakthrough time obtained from adsorption isotherms shows a volcano-type dependence on the temperature with a maximum NOx storage capacity occurring $350^{\circ}C$ and with a maximum breakthrough time occurring $400^{\circ}C$ at all GHSVs investigated in this study. Also, maximum ratio of $NO_2$ to NO is obtained at $400^{\circ}C$ with a GHSV of $75,000\;hr^{-1}$ Lean/rich cycle of 100 s lean and 5 s rich used with a concentration of 1.33% of $H_2$ and 4% of CO in the rich phase is found to be optimum at operating temperature of $350^{\circ}C$ and a GHSV of $50,000\;hr^{-1}$.

• Journal of the Korean Chemical Society
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• v.20 no.5
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• pp.351-357
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• 1976

Adsorption isotherms of benzene and p-xylene on both of Spheron 6 (a graphitized carbon black) and Alucer (Alumina) are obtained at various temperatures using a sensitive quartz beam microbalance. From these isotherms BET plots are made to obtain the molecular areas of these adsorbates. On the Spheron 6, the molecular area of p-xylene remains constant until the temperature is increased up to $19^{circ}C$, increases abruptly at $19^{circ}C$ through $19.2^{circ}C$, and then again remains constant thereafter. On the other hand, adsorbed benzene molecules give a quite temperature-independent molecular area. The results are interpreted as the adsorbed p-xylene molecules and benzene molecules are localized on the adsorbents with compact packing, while it gains a hindered-rotational degree of freedom at the expense of vibrational one at the higher temperatures. This peculiar behavior of adsorption is considered as due to the interactions between benzene rings of adsorbents and graphite surface. Molecular areas of these adsorbates on Alucer M. A. increase gradually with temperature, indicating that the adsorbed molecules are unlocalized.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1625-1631
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• 2013

We report a facile synthetic approach of high-quality chromium(III) terephthalate [MIL-101(Cr)] by acetate-assisted method in the absence of toxic HF. Results indicate that the morphology and surface area of the MIL-101(Cr) can be tuned by modifying the molar ratio of acetate/$Cr(NO_3)_3$. The Brunauer-Emmett-Teller (BET) surface area of MIL-101(Cr) synthesized at the optimized condition can exceed 3300 $m^2/g$. It is confirmed that acetate could promote the dissolution of di-carboxylic linker and accelerate the nucleation ratio. So the pure and small size of MIL-101(Cr) with clean pores can be obtained. $CO_2$, $CH_4$ and $N_2$ adsorption isotherms of the samples are studied at 298 K and 313 K. Compared with the traditional method, MIL-101(Cr) synthesized by acetate-assisted method possess enhanced $CO_2$ selective adsorption capacity. At 1.0 bar 298 K, it exhibits 47% enhanced $CO_2$ adsorption capacity. This may be attributed to the high surface area together with clean pores of MIL-101(Cr).

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.2
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• pp.180-190
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• 2005

The PSA cycle was performed for the separation of binary gas mixture $H_2/Ar$ (80%/20%) using the six-step two-bed process. Adsorption equilibrium contains a LRC model for equilibrium adsorption isotherms and a LDF model for mass transfer. Aspen ADSIM, simulator was applied to predict the separation performance. The effect of cycle parameters such as feed rate, adsorption pressure and P/F ratio on the separation of hydrogen has been studied in experiment and simulation. In the results, maximize the recovery of hydrogen as a high purity was 13LPM feed flowrate, 120sec adsorption time, 11atm adsorption pressure and 0.1 P/F ratio in a cyclic steady-state come out since 10th cycle.

• Carbon letters
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• v.8 no.4
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• pp.299-306
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• 2007

Four stream- activated carbons were prepared by carbonizing apricot stones at $600^{\circ}C$ followed by gasification with steam at $950^{\circ}C$ to burn-off's=17, 32, 49 and 65%. The textural parameters of these activated carbons were determined from nitrogen adsorption results at 77 K. The total pore volume and the mean pore radius increased with the increase of % burn-off whereas the surface area increased with the increase of burn- off from 17 to 32 and further to 49%. Further increase of burn-off to 65% was associated with a considerable decrease in surface area as a result of pronounced pore widening due to pore erosion. The surface pH values of the carbons investigated range between 7.1 and 8.2. The adsorption of oxamyl onto the activated carbon followed pseudo-second order kinetics and the equilibrium adsorption isotherms fitted Langmuir adsorption model. The adsorption of oxamyl proved to be of the physical type and took place in non-micropores. The amount of oxamyl adsorbed expressed as $q_m$ depends to a large extent to the surface area located in non-micropores $S^{\propto}\;_n$, where a straight line relationship passing through the origin was obtained.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.167.2-167.2
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• 2014

In this work, ZnO shell on mesoporous $SiO_2$ ($ZnO/SiO_2$) was prepared by atomic layer deposition (ALD). Diethylzinc (DEZ) and $H_2O$ were used as precursor of ZnO shell. $ZnO/SiO_2$ sample was characterized by X-ray diffraction (XRD), N2 sorption isotherms, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR). $ZnO/SiO_2$ showed higher adsorption capacity of MB than that of bare mesoporous $SiO_2$ and the adsorption capacities of $ZnO/SiO_2$ could be regenerated by UV exposure through the photocatalytic degradation of the adsorbed MB. This system could be used for removing organic dye from water by adsorption and reused after saturation of adsorption due to its photocatalytic regeneration.