• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.604-610
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• 2023

The nitrogen reduction reaction (NRR), which produces NH₃ by reducing N₂ under ambient conditions, is attracting attention as a promising technology that can reduce energy consumption in industrial processes. We investigated the adsorption behaviors at various active sites on the Ni (100) surface, which is widely used among catalytic metal surfaces capable of adsorbing and activating N₂, based on density-functional theory calculations. We also investigated two N₂ adsorption structures, so-called end-on and side-on structures. We find that for the end-on case, N₂ is adsorbed on a top site, and the reaction proceeded in a distal pathway, while for the side-on case, N₂ is adsorbed on a bridge site, and the reaction proceeded with enzymatic pathway. Finally, this study provides insight into the adsorption of metal catalyst surfaces for the NRR reactions based on the calculated Gibbs free energy profiles of the thermodynamically most favorable pathways.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.123-130
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• 2005

Zeolite X adsorbents with large surface area were prepared for using oxygen PSA adsorbent. Selective adsorption performance of nitrogen on the synthesized zeolite X adsorbent was improved by the cation exchange of adsorbent. The zeolite X which had over $650m^2/g$ surface area was synthesized at the conditions of $SiO_2\;:\;Na_2O\;:\;H_2O\;:\;Al_2O_3$ = 2.5 : 3.5 : 150 : 1 mole ratio, $98^{\circ}C$ temperature and 18 h synthesized time in 50 L reactor. The metal ions Li, Ag, Ca, Br, Sr, etc. were investigated for ion exchange with zeolite X. Ag ion was showed the highest ion exchange rate among these metal ions and all metal ions were exchanged with Na ion at equivalent rate. Compared with the NaX adsorbent, the ion exchanged zeolite X adsorbent remarkably improved its adsorption performance of nitrogen at the conditions of $10{\sim}40^{\circ}C$ temperature and 0~9 atm pressure. At an equilibrium pressure under 0.5 atm, adsorption performance of nitrogen on the ion exchanged zeolite adsorbent increased in the order of Ag > Li > Ca > Sr> Ba > K, whereas at an equilibrium pressure over 1 atm showed in the order of Li > Ag > Ca > Sr > Ba > K. Nitrogen/oxygen separation factor of Li ion exchanged zeolite X adsorbent was 13.023 at the partial pressure of nitrogen/oxygen gas mixture similar to air and $20^{\circ}C$ adsorption temperature.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.798-802
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• 1998

Carbon granules were prepared by granulating a mixture of coconut shell powder and coal tar solution, and then by carbonizing at different temperatures. To control micropores of the carbonized granules, the deposition time of benzene vapor under nitrogen atmosphere was varied. For each prepared sample, SEM morphology and true density were investigated. The adsorption rates on the granules were measured with respect to oxygen and nitrogen by means of the Cahn D-200 system. Diffusivity, selectivity and amount of equilibrium adsorption for the gases were obtained from the measurement of adsorption rate. Based on the analysis of the adsorption characteristics, the optimum temperature and the deposition time for preparation of the molecular sieve carbon granules were found to be $800^{\circ}C$ and 10 minutes, respectively. At these optimal conditions, the selectivity coefficient, 26.4, 0f oxygen and nitrogen was obtained.

• Carbon letters
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• v.3 no.4
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• pp.187-191
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• 2002

In the present research, we prepared the activated carbon (AC) sorbents to remove gas-phase mercury. The mercury adsorption of virgin AC, chemically treated AC and fly ash was performed. Sulfur impregnated and sulfuric acid impregnated ACs were used as the chemically treated ACs. A simulated flue gas was made of SOx, NOx and mercury vapor in nitrogen balance. A reduced mercury adsorption capacity was obtained with the simulated gas as compared with that containing only mercury vapor in nitrogen. With the simulated gas, the sulfuric acid treated AC showed the highest performance, but it might have the problem of corrosion due to the emission of sulfuric acid. It was also found that the high sulfur impregnated AC also released a portion of sulfur at $140^{\circ}C$. Thus, it was concluded that the low sulfur impregnated AC was suitable for the treatment of flue gas in terms of stability and efficiency.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2930-2934
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• 2009

Surface-enhanced Raman Scattering (SERS) spectroscopy is applied to the study of the adsorption of benzoimidazolic fungicides benzimidazole (BIZ) and thiabendazole (TBZ) on silver mirrors. The influence of pH on the adsorption mechanism was investigated. In case of BIZ, two different adsorption mechanisms are deduced depending on the experimental conditions: via the $\pi$ electrons of the ring in neutral conditions and through an ionic pairing of protonated nitrogen atom with the chloride adsorbed on the metal surface. The SERS spectra of TBZ revealed that most molecules were adsorbed on silver surface by the ${\pi}$ electrons in neutral and acidic conditions but in acid conditions, some molecules were adsorbed via the sulfur and nitrogen atoms tilted slightly to the surface.

• Clean Technology
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• v.12 no.4
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• pp.217-223
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• 2006

The operating variables of a desorption step were experimentally investigated tor the cycle of the process made up of benzene adsorption, steam desorption, and drying step. The effect of adsorbent regeneration depending on existence and nonexistence of drying step was studied by breakthrough curves obtained in the adsorption step of the second cycle. The duration of drying step was determined by the experimental results. In case that the amount of nitrogen gas was fixed, the regeneration efficiency increased with the amount of steam. However, the effect of steam decreased as the amount of nitrogen increased. Therefore, it would be possible to predict the optimum amount of steam comparing the amount of nitrogen gas with amount of steam in economic view.

• Journal of the Korean Institute of Gas
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• v.8 no.4 s.25
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• pp.36-41
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• 2004

The breakthrough curve was obtained to evaluate separation efficiency of clinoptilolite as an methane/nitrogen separation adsorbent. The Ca-exchanged clinoptilolite showed improved separation efficiency. The nitrogen adsorption capacity of Ca-clinoptilolite was increased with decreasing temperature. The temperature was decreased from 293K to 253K(feed gas flow rate : 670ml/min, pressure : 333kPa). The adsorption capacity is increased with increasing pressure. The pressure was increased from 333kPa to 700kPa(feed gas flow rate : 670ml/min, temperature : 253K, 293K).

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.2
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• pp.34-41
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• 1999

Adsorption of cationic polyacrylamide dry strength resins onto the surface of papermaking fibers and fines is critical for their effective utilization. Since dry strength resins are frequently employed when recycled fibers containing a great deal of fines are used as a raw material, their adsorption characteristic onto the recycled fiber fines is of great importance. In this study, effects of recycling on adsorption characteristics of cationic polyacrylamide onto primary and secondary fines were examined. Never dried bleached hardwood kraft pulp was beaten and dried for recycling. In each recycling step the adsorption characteristic of a cationic PAM onto primary and secondary fines was evaluated by kjeldahl nitrogen analysis method. The influence of recycling on water retention value and carboxyl content along with the sheet density and tensile strength was examined. Secondary fines of never dried pulp adsorbed twice as much of C-PAM as the primary fines, however, the adsorption capacity of the secondary fines decreased rapidly during the course of recycling and showed lower adsorption capacily than primary fines.

• Carbon letters
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• v.19
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• pp.12-22
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• 2016

Date palm leaflets were used as a precursor to prepare dehydrated carbon (DC) via phosphoric acid treatment at 150℃. DC, acidified with H₃PO₄, was converted to activated carbon (AC) at 500℃ under a nitrogen atmosphere. DC shows very low surface area (6.1 m²/g) while AC possesses very high surface area (829 m²/g). The removal of lisinopril (LIS) and chlorpheniramine (CP) from an aqueous solution was tested at different pH, contact time, concentration, and temperature on both carbons. The optimal initial pH for LIS removal was 4.0 and 5.0 for DC and AC, respectively. However, for CP, initial pH 9.0 showed maximum adsorption on both carbons. Adsorption kinetics showed faster removal on AC than DC with adsorption data closely following the pseudo second order kinetic model. Adsorption increases with temperature (25℃–45℃) and activation energy (E_a) is in a range of 19–25 kJ mol/L. Equilibrium studies show higher adsorption on AC than DC. Thermodynamic parameters show that drug removal is endothermic and spontaneous with physical adsorption dominating the adsorption process. Column adsorption data show good fitting to the Thomas model. Despite its very low surface area, DC shows ~70% of AC drug adsorption capacity in addition of being inexpensive and easily prepared.

• Carbon letters
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• v.3 no.4
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• pp.198-204
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• 2002

In this paper, impregnated activated carbon fiber (IACF) was manufactured to pitch-based activated carbon fibers (ACF) with potassium hydroxide (KOH) by using wet impregnation method to raise nitrogen oxides ($NO_x$) adsorptivity. The properties of IACF were observed using EPMA, TGA and DSC and $NO_x$ adsorptivity was observed at high and low temperature. Before and after adsorption was analyzed using ToF-SIMS for examine surface characterization of adsorbed $NO_x$. The results showed that the better adsorptivity appeared for increasing KOH ratio. So, $NO_x$ adsorptivity showed result that is proportional between KOH and the adsorbed amount. On the other hand, adsorbent that manufactured without washing was better $NO_x$ adsorptivity than adsorbent that manufactured with washing. The behavior of adsorption show that crossing time of NO and $NO_2$ delayed for a rising adsorptivity. And NO ratio increased but $NO_2$ ratio decreased according as KOH ratio increases. $NO_x$ was confirmed through surface analysis that remain in $NO_2^-$ and $NO_3^-$ form on IACF surface.