• Korean Journal of Chemical Engineering
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• 제35권12호
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• pp.2468-2473
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• 2018

Nitrogen-doped activated carbon fibers (ACFs) were prepared by chemical vapor deposition using melamine powder and acetonitrile for introducing quaternary nitrogen on the commercial ACFs, subsequently heated at $950^{\circ}C$ and activated by steam. Adsorption experiments of nitrate in aqueous solution were also conducted to evaluate adsorption capacity of the prepared ACFs using ion chromatography. The amount of introduced nitrogen content and nitrogen species on activated carbon fibers was examined by CHN elemental analyzer and X-ray photoelectron spectroscopy, respectively. As a result, adsorption capacity of quaternary nitrogen-doped ACF (ST-ML-AN-ST) was 0.75 mmol/g, indicating ca. two-times higher than that of untreated ACF (0.38 mmol/g). According to the adsorption data, the Langmuir isotherm model was the best fit. The prepared samples were also regenerated using hydrochloric acid. After regeneration, the adsorption capacity of the nitrogen-doped ACF (ST-ML-AN-ST) showed ca. 80% on average, implying that a portion of nitrates was adsorbed on the prepared ACFs irreversibly.

• Korean Chemical Engineering Research
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• 제46권6호
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• pp.1029-1038
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• 2008

전이금속 산화물의 전구체가 들어있는 합성모액을 수열 반응시켜 전이금속 산화물이 고정된 하이드로탈사이트를 제조하여 이들에 대한 이산화질소의 흡착 성질을 조사하였다. 전이금속 산화물의 분산도, 이산화질소의 흡착량 및 흡착상태를 XRD, SEM, XPS, 질소 흡착등온선, 중량식 흡착법, FT-IR, 승온탈착법으로 조사하였다. 전이금속 산화물은 주로 하이드로탈사이트의 표면에 분산 담지되었으며, 철과 니켈 산화물이 고정된 하이드로탈사이트에 이산화질소가 많이 흡장되었다. 철 산화물이 표면에 분산되어 담지되면 이산화질소의 흡장량이 많지만, 철 산화물이 지나치게 많이 담지되면 덩어리져서 표면의 염기점을 차폐하므로 이산화질소의 흡장량이 오히려 줄어들었다. 철 산화물의 고정량이 적절하면 하이드로탈사이트에서 이산화질소의 흡장세기는 약해지지만, 흡장량은 많아지고 수열 안정성이 증진되었다.

• 대한건축학회논문집:구조계
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• 제34권3호
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• pp.37-42
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• 2018

The use of fly ash in construction materials is increasing worldwide due the various advantages of using it, such as to produce durable concrete, or to use less cement and thus lower carbon dioxide emissions. The quality of fly ash is often determined by loss on ignition value (LOI), where an upper limit of LOI is set in each country for quality control purpose. However, due to many reasons, production of high LOI fly ash is increasing that cannot be utilized in concrete, ending up in landfill. In this study, the effect of fly ash use in cementitious materials on nitrogen oxides adsorption is examined. In particular, the effect of using high LOI, and thus high carbon content fly ash on nitrogen oxides adsorption is investigated. The results suggest that the higher carbon content fly ash is related to higher nitrogen dioxide adsorption, although normal fly ash was also more effective in nitrogen dioxide adsorption than ordinary portland cement. Also, higher replacement rate of up to 40% of fly ash is beneficial for nitrogen dioxide adsorption. These results demonstrate that high carbon fly ash can be used as construction materials in an environmentally friendly way where strength requirement is low and where nitrogen oxides emissions are high.

• 한국환경과학회지
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• 제20권2호
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• pp.215-222
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• 2011

The adsorption behavior of nitrate nitrogen was investigated from aqueous solution using char prepared from oak chip. The removal rate of nitrate nitrogen was found to be dependent on temperature and it is increased as the temperature increase. Adsorption equilibrium data of nitrate nitrogen on oak char. reasonably fitted Langmuir and Freundlich isotherm models. The adsorption energy obtained from D-R model was 12.5 kJ/mole at $20^{\circ}C$ indicating an ion exchange process as primary adsorption mechanism. Thermodynamic parameters such as ${\Delta}G^o$, ${\Delta}H^o$, and ${\Delta}S^o$ were -23.76 kJ/mole, 26.1 kJ/mole and 89.7 J/K mole at $20^{\circ}C$, respectively, indicated that the nature of nitrate nitrogen adsorption is spontaneous and endothermic.

• 한국물환경학회지
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• 제24권3호
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• pp.311-316
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• 2008

This study aimed to obtain equilibrium concentration on adsorption removal of ammonia nitrogen by activated carbon, to express the adsorption characteristics following Freundlich isotherm and also, based on the value obtained, to investigate the relationship between physical characteristics of activated carbon and dynamics of ammonia nitrogen removal by obtaining rate constant and effective pore diffusivity. The results summarized from this study are as follows. It was noted that powdered activated carbon showed better adsorption ability than granular activated carbon. The value of constant (f) of Freundlich isotherm of powered activated carbon was $4.6{\times}10^{-8}$ which is bigger than that of granular activated carbon. The adsorption rate constant on ammonia nitrogen of powered activated carbon with high porosity and low effective diameter was highest as 0.416 hr-1 and the effective pore diffusivity ($D_e$) was lowest as $1.17{\times}10^{-6}cm^2/hr$, and the value of ammonia nitrogen adsorption rate constant of granular activated carbon was $0.149{\sim}0.195hr^{-1}$. It was revealed that, with the same amount of dosage, the adsorptive power of activated carbon with lower effective diameter and bigger porosity was better and its rate constant was also high. With a little adsorbent dosage of 2 g, there was no difference removal ability of ammonia nitrogen as change of adsorption properties.

• 공업화학
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• 제35권1호
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• pp.8-15
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• 2024

본 연구에서는 활성탄소의 테트라사이클린 흡착성능을 향상시키기 위해 5, 10, 및 15분의 시간에 따른 질소 플라즈마 처리를 실시하였다. 모든 질소 플라즈마 처리된 활성탄소는 미처리 활성탄소와 비교하여 테트라사이클린 흡착성능이 개선되었다. 이는 활성탄소에 도입된 질소 작용기가 테트라사이클린과 π-π 상호작용 및 수소 결합을 통하여 화학흡착을 야기하기 때문이다. 특히, 80 W 및 50 kHz의 질소 플라즈마 처리에서, 10분 동안 처리된 활성탄소가 가장 우수한 흡착성능을 가졌다. 이 때, 활성탄소 표면의 질소 함량은 2.03%이며 비표면적은 1,483 m²/g까지 증가하였다. 이렇게 질소플라즈마 처리에 의해 개선된 활성탄소는 물리 및 화학 흡착성능이 향상되었다. 또한, 흡착 실험 결과가 Langmuir 흡착등온식과 유사 2차 반응속도식에 잘 부합하므로, 질소 플라즈마 처리된 활성탄소의 테트라사이클린 흡착은 단분자층으로 이루어지는 화학 흡착이 주도적으로 일어나는 것으로 판단하였다. 결과적으로, 질소 플라즈마 처리된 활성탄소는 주도적인 화학 흡착과 더불어 물리 흡착의 시너지 효과로 수중에서 테트라사이클린을 효율적으로 제거하는 흡착재로 사용될 수 있다.

• 유기물자원화
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• 제24권1호
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• pp.59-63
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• 2016

본 연구는 제올라이트를 이용한 수중의 암모니아성질소 및 질산성질소 제거특성을 알아보고자 수중의 암모니아성질소 및 질산성질소의 흡착제거에 대한 흡착변화를 조사하였다. 연구결과 암모니아성질소 흡착제거에 대한 제올라이트의 최대흡착량은 120mg/g(암모니아성질소 / 제올라이트 무게)임을 알 수 있었고, 암모니아성 및 질산성질소의 흡착에 대해 Freundlich식과 Langmuir식을 비교해 보았을 때 Langmuir 등온흡착식에 더 일치함을 알 수 있었다. 이는 제올라이트가 피흡착제와 이온교환 및 단층흡착함을 의미한다. 또한, pH 변화에 따른 암모니아성질소의 처리효율은 pH 7 > pH 5 > pH 9 > pH 3 순임을 알 수 있었으며, 제올라이트가 암모니아성질소 인공폐수의 pH를 상승시킴을 알 수 있었다.

• International Journal of Concrete Structures and Materials
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• 제8권4호
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• pp.327-333
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• 2014

The objective of this work was to examine the influence of carbonation on the microstructure of cement materials. Different materials, which were CEM I mortar and paste, CEM II mortar and paste, were carbonated at $20^{\circ}C$, 65 % relative humidity and 20 % of $CO_2$ concentration. The specific surface area and pore size distribution were determined from two methods: nitrogen adsorption and water adsorption. The results showed that: (1) nitrogen adsorption and water adsorption do not cover the same porous domains and thus, we observed conflicts in the results obtained by these two techniques; (2) the CEM II based materials seemed to be more sensible to a creation of mesoporosity after carbonation than the CEM I based materials. The results of this study also helped to explain why observations in the literature diverge greatly on the influence of carbonation on specific surface area.

• Carbon letters
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• 제16권1호
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• pp.57-61
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• 2015

Carbon aerogel is a porous carbon material possessing high porosity and high specific surface area. Nitrogen doping reduced the specific surface area and micropores, but it furnished basic sites to improve the $CO_2$ selectivity. In this work, N-doped carbon aerogels were prepared with different ratios of resorcinol/melamine by using the sol-gel method. The morphological properties were characterized by scanning electron microscopy (SEM). Nitrogen content was studied by X-ray photoelectron spectroscopy (XPS) and the specific surface area and micropore volume were analyzed by $N_2$ adsorption-desorption isotherms at 77 K. The $CO_2$ adsorption capacity was investigated by $CO_2$ adsorption-desorption isotherms at 298 K and 1 bar. Melamine containing N-doped CAs showed a high nitrogen content (5.54 wt.%). The prepared N-doped CAs exhibited a high $CO_2$ capture capacity of 118.77 mg/g (at resorcinol/melamine = 1:0.3). Therefore, we confirmed that the $CO_2$ adsorption capacity was strongly affected by the nitrogen moieties.

• Bulletin of the Korean Chemical Society
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• 제24권12호
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• pp.1814-1818
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• 2003

$Li^+$ and $H^+$ co-exchanged LSXs (Li-H-LSX) with various ratios of $Li^+$ and $H^+$ were prepared, and those adsorption characteristics of nitrogen and oxygen were compared with Li-Na-LSX and Li-Ca-LSX. Li-H-LSX showed higher nitrogen capacity and selectivity than that of Li-Na-LSX in the wide range of Li-exchanged ratio. The nitrogen capacity of Li-Ca-LSX was slightly higher than that of fully Li- or Ca-exchanged LSX (Li- LSX or Ca-LSX). However, Li-Ca-LSX showed low nitrogen/oxygen adsorption selectivity until the Li content reached about 80%, which was a tendency near that of Ca-LSX.