• Carbon letters
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• 제4권2호
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• pp.64-68
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• 2003

A study on the electrosorption of uranium ions onto a porous activated carbon fiber (ACF) was performed to treat uraniumcontaining lagoon sludge. The result of the continuous flow-through cell electrosorption experiments showed that the applied negative potential increased the adsorption kinetics and capacity in comparison to the open-circuit potential (OCP) adsorption for uranium ions. Effective U(VI) removal is accomplished when a negative potential is applied to the activated carbon fiber (ACF) electrode. For a feed concentration of 100 mg/L, the concentration of U(VI) in the cell effluent is reduced to less than 1 mg/L. The selective removal of uranium ions from electrolyte was possible by the electrosorption process.

• Carbon letters
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• 제11권2호
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• pp.131-136
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• 2010

Propellant waste was impregnated on the surface of activated carbon fiber and heat-treated at different temperature to introduce newly developed functional groups on the ACF surface. Functional groups of nitrogen and oxygen such as pyridine, pyridone, pyrrol, lacton and carboxyl were newly introduced on the surface of modified activated carbon fiber. The porosity, specific surface area, and morphology of those modified ACFs were changed as increasing the heat-treated temperature from 200 to $500^{\circ}C$. The optimum heat-treatment temperature was suggested to $500^{\circ}C$, because lower temperature given rise to the decrease of specific surface area and higher temperature resulted in the decrease of weight loss. Propellant waste can be used as an useful surface modifier to porous carbons.

• Carbon letters
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• 제15권1호
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• pp.1-14
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• 2014

Carbon nanofibers (CNFs) with diameters in the submicron and nanometer range exhibit high specific surface area, hierarchically porous structure, flexibility, and super strength which allow them to be used in the electrode materials of energy storage devices, and as hybrid-type filler in carbon fiber reinforced plastics and bone tissue scaffold. Unlike catalytic synthesis and other methods, electrospinning of various polymeric precursors followed by stabilization and carbonization has become a straightforward and convenient way to fabricate continuous CNFs. This paper is a comprehensive and brief review on the latest advances made in the development of electrospun CNFs with major focus on the promising applications accomplished by appropriately regulating the microstructural, mechanical, and electrical properties of as-spun CNFs. Additionally, the article describes the various strategies to make a variety of carbon CNFs for energy conversion and storage, catalysis, sensor, adsorption/separation, and biomedical applications. It is envisioned that electrospun CNFs will be the key materials of green science and technology through close collaborations with carbon fibers and carbon nanotubes.

• 한국습지학회지
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• 제18권1호
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• pp.39-44
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• 2016

최근 커피 이용량이 증가하면서 폐커피가루의 활용에 대한 관심이 환경공학 분야에서 높아지고 있다. 본 연구에서는 폐커피가루를 재활용하여 오염물질에 대한 흡착제로서의 사용 가능성을 평가하기 위하여 액상의 유기 오염물질(메틸렌 블루)에 대한 흡착평형실험 및 흡착속도실험을 수행하였고, 입상활성탄 및 분말활성탄을 이용한 실험결과와 비교하였다. 실험 결과, 흡착평형의 경우 세 종류의 흡착제 모두 Langmuir 식에 잘 맞는 것으로 확인되었으며, 최대흡착량은 분말활성탄(178.6 mg/g), 폐커피가루(60.6 mg/g), 입상활성탄(15.6 mg/g) 순으로 확인되었다. 흡착속도실험에서도 유사 1차식 및 유사 2차식 모두에서 폐커피가루가 입상활성탄보다 우수한 것으로 확인되었다. 이는 폐커피가루의 입자 크기가 입상활성탄보다 작으며 표면이 입상 및 분말활성탄과 같이 다공성 특성을 띄고 있기 때문인 것으로 판단되었다.

• Carbon letters
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• 제15권1호
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• pp.71-76
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• 2014

Activated carbon nanofibers (ACNF) were prepared from polyacrylonitrile (PAN)-based nanofibers using $CO_2$ activation methods with varying activation process times. The surface and structural characteristics of the ACNF were observed by scanning electron microscopy and X-ray diffraction, respectively. $N_2$ adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller and Dubinin-Radushkevich equations. As experimental results, many holes or cavernous structures were found on the fiber surfaces after the $CO_2$ activation as confirmed by scanning electron microscopy analysis. Specific surface areas and pore volumes of the prepared ACNFs were enhanced within a range of 10 to 30 min of activation times. Performance of the porous PAN-based nanofibers as an electrode for electrical double layer capacitors was evaluated in terms of the activation conditions.

• Carbon letters
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• 제19권
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• pp.99-103
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• 2016

Porous carbons have attracted much attention for their novel application in gas storage. In this study, porous graphite nano-fiber (PGNFs)-based graphite nano fibers (GNFs) were prepared by KOH activation to act as adsorbents. The GNFs were activated with KOH by changing the GNF/KOH weight ratio from 0 through 5 at 900℃. The effects of the GNF/KOH weight ratios on the pore structures were also addressed with scanning electron microscope and N₂ adsorption/desorption measurements. We found that the activated GNFs exhibited a gradual increase of CO₂ adsorption capacity at CK-3 and then decreased to CK-5, as determined by CO₂ adsorption isotherms. CK-3 had the narrowest micropore size distribution (0.6–0.78 nm) among the treated GNFs. Therefore, KOH activation was not only a significant method for developing a suitable pore-size distribution for gas adsorption, but also increased CO₂ adsorption capacity as well. The study indicated that the sample prepared with a weight ratio of ‘3’ showed the best CO₂ adsorption capacity (70.8 mg/g) as determined by CO₂ adsorption isotherms at 298 K and 1 bar.

• Carbon letters
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• 제14권4호
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• pp.234-242
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• 2013

Potassium hydroxide-activated carbons (CK21, CK11, and CK12) were prepared from pistachio nutshells. Physicochemical properties of activated carbons were characterized by TGA, $pH_{pzc}$, Fourier transform infrared spectroscopy, scanning electron microscopy, and $N_2$-adsorption at $-196^{\circ}C$. The examinations showed that activated carbons have high surface area ranging between 695-1218 $m^2/g$, total pore volume ranging between 0.527-0.772 mL/g, and a pore radius around 1.4 nm. The presence of acidic and basic surface C-O groups was confirmed. Batch adsorption experiments were carried out to study the effects of adsorbent dosage, temperature, initial concentration of adsorbate, and contact time on deltamethrin adsorption by activated carbons. The kinetic studies showed that the adsorption data followed a pseudo-second order kinetic model. The Langmuir model showed a maximum adsorption capacity of 162.6 mg/g at $35^{\circ}C$ on CK12. Thermodynamic studies indicated that adsorption was spontaneous and increased with temperature, suggesting an endothermic process.

• 공업화학
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• 제30권1호
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• pp.23-28
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• 2019

탄소 실의 표면에 코팅 된 3차원 다공성 그래핀으로 구성된 슈퍼커패시터 케이블 소자를 보고하고자 한다. 그래핀의 3D 다공성 구조는 그래핀옥사이드로 코팅된 탄소 실을 사용하여 마이크로웨이브 활성화 방법에 의해 제작하였다. 마이크로파 조사의 사용은 환원제 없이 그래핀옥사이드를 환원된 그래핀옥사이드로 전환시키고 그래핀 시트를 박리 및 다공성 그래핀 시트로 활성화시켰다. 두 개의 와이어 전극을 고분자 겔 전해질과 결합하여 성공적으로 케이블 구조 형태의 슈퍼커패시터 소자를 제작하였다. 슈퍼커패시터 케이블은 매우 유연하기 때문에 다양한 형태의 장치로 변형될 수 있고 섬유 품목으로 통합될 수 있다. 주사 속도 10 mV/s에서 38.1 mF/cm의 높은 정전용량이 얻어졌다. 이용량은 500 mV/s에서 원래 값의 88%를 유지하였다. 장수명특성은 구부러진 형태에서도 10,000회 동안 충전/방전 과정을 반복함으로써 96.5%의 높은 정전용량 유지율을 증명하였다.

• Journal of Electrochemical Science and Technology
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• 제10권4호
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• pp.387-393
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• 2019

Activated carbons (ACs) are considered important electrode materials for supercapacitors because their large specific surface areas lead to high charging capacities. In the conventional synthesis of ACs, a substantial amount of carbon is lost during carbonization of a precursor. The development of a method to synthesize ACs in high yield would lower their manufacturing cost. Here, we demonstrate the synthesis of high-specific-surface-area NaOH-AC from carbon prepared via a hydrothermal carbonization (HTC) route, with a higher yield than that achieved through conventional pyrolysis carbonization. The amorphous carbon was derived from HTC of sugar and subsequently activated at 800℃ with various NaOH etchant/C ratios under a N₂ atmosphere. The AC prepared at 4:1 NaOH/C exhibited the highest surface area (as high as 2,918 ㎡ g^-1) and the highest specific capacitance (157 F g^-1 in 1 M aqueous Na₂SO₄ electrolyte solution) among the NaOH-AC samples prepared in this work. On the basis of their high specific capacitance, the NaOH-ACs prepared from HTC sugar are suitable for use as electrode materials for supercapacitors.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2002년도 추계총회 및 학술발표회
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• pp.54-54
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• 2002