A highly functional, environmentally friendly carbonaceous adsorbent material using black liquor (a by-product from the pulp manufacturing) was produced and characterized. This study showed the effect of self-chemical activation driven by inherent alkali, originated from the unique composition of black liquor. A preparation of the micropore-dominant activated carbon was made in an easy and simple manner. The specific surface areas of samples were found to be 718–1591 m2/ g variated upon heat treatment conditions. The sample activated at 850 °C (50 min as retention time) showed the maximum specific surface area of 1591 m2/ g with 13.6% as a production yield. Considering the factors influencing pore structure of activated carbon materials in this study, it was confirmed that mesopore-related surface area increased gradually as the activation temperature and retention time increased. It is noteworthy to address that economically valuable micropore-dominant activated carbon can be produced by a simple heat treatment of the waste material, black liquor. The activated carbon sample derived from black liquor can be applied to various fields, such as environment and energy storage.

본 연구에서는 “이온젤” 이라고 불리는 고분자 기반의 PVA(polyvinyl alcohol) 기반의 고체 전 해질에 이온성 액체 BMIMBF4 (1-buthyl-3-methylimidazolium tetrafluoroborate)를 첨가하여 제조한 전 고체 전해질과 활성탄소와 금속유기골격체 복합재료 기반의 전극 재료를 이용하여 슈퍼커패시터를 제작 하였으며, 유기골격체의 유 무에 따른 전기화학적 특성을 분석하여 보았다. 슈퍼커패시터의 전기화학적 특 성은 순환전압전류법(CV), 전기화학적 임피던스 분광법(EIS) 및 전정류 충·방전법(GCD)을 통하여 비교 및 분석하여 보았다. 그 결과로, 금속유기골격체가 함유되지 않은 슈퍼커패시터의 전기용량값은 380 F/g 으로 확인 할 수 있었고, 이 값은 금속유기골격체를 첨가하였을 때 340 F/g로 감소하는 현상을 확인할 수 있었 다. 이러한 결과로 1 wt%의 금속유기골격체의 함유량은 전기화학적 특성 감소에 영향을 주는 것으로 사료 되며 이러한 결과를 바탕으로 금속유기골격체의 첨가량을 최적화 할 필요가 있다고 판단된다

The reduced graphene oxide (rGO)/activated carbon (AC) composites are coated on the aluminum substrate using spray coating technique to fabricate nanocarbon-based supercapacitor. Polymer-based solid-state xanthan-gum/Na2SO4 electrolyte is also introduced to increase stability of the supercapacitor. The electrochemical properties of the supercapacitor are evaluated using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge tests. The highest capacitance value of the rGO/AC composite-based supercapacitor is 120 F/g. The rGO/AC composite-based supercapacitor has also retained ~ 85% of its initial capacitance value after 3000 galvanostatic charge/discharge cycles.

Increasing demand for fossil fuels is associated with massive atmospheric CO2 levels. Considering that numerous studies have been published with CO2 capturing techniques, utilizing techniques are yet in early stage with financial or technical issues. As a part of chemical conversion in CO2 utilization, this paper investigated the performance of a CO2 and H2O mixture (CHM) onto activated carbon fibers (ACF) for surface modification. CHM-treated ACF samples were prepared at a pressure of 20 bar with 100 °C of water vapor and 750 μL of CO2 for 1 h through the gas-phase, and labeled as C-ACF850. For the control sample, N-ACF850 was also prepared by the impregnation of nitric acid. Physiochemical analyses revealed that the overall characteristics of C-ACF850 lay between ACF850 and N-ACF850. C-ACF850 experienced minimized surface area decrement (21.92% better than N-ACF850), but increased surface functional groups (50.47% better than ACF850). C-ACF850 also showed preferable adsorption efficiency on selected metals, in which case both physical and chemical properties of adsorbent affect the overall adsorption efficiency. In this regard, a novel applicability of CHM may present an appealing alternative to traditionally used strong acids.

In this study, we prepared ACFs with a high specific surface area from various precursors (rayon, pitch, and oxidized polyacrylonitrile-based fibers) by a steam-activation technique and investigated the effects of the micropore and mesopore fraction on 2-CEES adsorption behaviors. The activation time was precisely controlled so that the activation yield was in the range of 35–40% to ensure the mechanical properties of the ACFs. The N2 adsorption isotherm characteristics at 77K were confirmed by Brunauer–Emmett–Teller, Barrett–Joyner–Halenda and non-local density functional theory equations. The adsorption capacities of the ACF were measured by breakthrough experiments in the gas phase (750 μg/mL of 2-CEES in N2 flow). The removal efficiency of the ACFs was evaluated and compared with that of AC. From the results, specific surface areas and total pore volume of the ACF were determined to be 1380–1670 m2/g and 0.61–0.82 cm3/g, respectively. It was also observed that various pore characteristics of ACF were found to be dependent on crystallite structure of each precursor. The break through time (C/C0 = 0.10) was in the order of Oxi-Pan-H-9-2 < Saratoga AC < Rayon-H-9-3 < Pitch-H-9-4. This indicates that 2-CEES adsorption capacity could be a function not only of specific surface area or total pore volume, but also of sub-mesopore volume fraction in the range of 1.5–2.5 nm of adsorbents.

Fibrous adsorbents, such as activated carbon fibers (ACF) have acknowledged advantages of rapid adsorption rate and ease of modification compared with granular and powdered adsorbents. Based on the surface modification of lyocell-based ACF, we observed different surface characteristics of ACF samples with variation in the mixing ratio and impregnation time of H3PO4, NaCl, and KMnO4 solution. For an engineering application, we also explored the adsorption characteristics of thusproduced ACF samples onto volatile organic compounds (VOCs). Isothermal adsorption experiments were performed using toluene and benzene as adsorbates. Results indicate that both physical and chemical surface properties have an effect on the adsorption of volatile organic compounds (VOCs).

Because of their excellent stability and highly specific surface area, carbon based materials have received attention as electrode materials of electrical double-layer capacitors(EDLCs). Biomass based carbon materials have been studied for electrode materials of EDLCs; these materials have low capacitance and high-rate performance. We fabricated tofu based porous activated carbon by polymer dissolution reaction and KOH activation. The activated porous carbon(APC-15), which has an optimum condition of 15 wt%, has a high specific surface area(1,296.1 m2 g−1), an increased average pore diameter(2.3194 nm), and a high mesopore distribution(32.4 %), as well as increased surface functional groups. In addition, APC has a high specific capacitance(195 F g−1) at low current density of 0.1 A g−1 and excellent specific capacitance(164 F g−1) at high current density of 2.0 A g−1. Due to the increased specific surface area, volume ratio of mesopores, and surface functional groups, the specific capacitance and high-rate performance increased. Consequently, the tofu based activated porous carbon can be proposed as an electrode material for high-performance EDLCs.

In this study, activated carbon with well-developed mesopores was fabricated using kenaf short fibers as a representative biomass. Concentrated phosphoric acid was selected as an activation agent to create highly developed porous structures, and pore development was observed to occur in relation to the weight ratio of phosphoric acid and kenaf. The pore characteristics of the kenaf-based activated carbon were determined using the N2/ 77K adsorption isotherm, and its microcrystalline structure was analyzed using X-ray diffraction. The highest specific surface area (1570 m2/g) was observed when the weight ratio of phosphoric acid to kenaf was 3:1, and the highest mesopore fraction (74%) was observed at 4:1. The carbonization yield was 45–35%, which is higher than that of commercial activated carbon. The production of porous carbon material by this method offers high potential for application because it can be controlled over a wide range of average pore diameter from 2.48 to 5.44 nm.

In this study, pitch crosslinked by oxygen function groups was made into activated carbon (AC) and pore structure was observed. The oxygen functional groups were introduced by the addition of waste PET for pitch synthesis. Activation agent ratios used to obtain the AC during the activation process were 1:1, 1:2 and 1:4 (pitch:KOH, w/w). The oxygen content in the prepared pitch was characterized by elemental analysis. Also, the molecular weight of pitch was investigated by MALDITOF. Specific surface area and micropore volume of the prepared AC were determined by the argon adsorption–desorption analysis and calculated using the Brunauer–Emmett–Teller and Horvath–Kawazoe equations, respectively. Micropore fraction of PET-free AC was smaller than that of PET-added AC. At high activation agent ratio, mesopores were created when the micropore structure collapsed. However, in the PET-added AC, due to the oxygen crosslinking effect, the micropore structure and micropore size were maintained even at a high activation agent ratio. Therefore, PET AC was found to have a higher micropore fraction than that of PET-free AC.

The present work is aimed at evaluating the kinetics and dynamic adsorption of methylene blue by CO2- activated carbon gels. The carbon gels were characterized by textural properties, thermal degradation and surface chemistry. The result shows that the carbon gels are highly microporous with surface area of 514 m2/g and 745 m2/g for resorcinol-to-catalyst ratios of 1000 (AC1) and 2000 (AC2), respectively. The kinetics data could be described by pseudo-first-order model, with a longer duration to attain equilibrium due to restricted pore diffusion as concentration increases. Also, AC1 exhibits insignificant kinetics with fluctuating adsorption with time at concentrations of 20 and 25 mg/L. However, AC1 reveals a better performance than AC2 in dynamic adsorption due to concentration gradient for molecules diffusion to active sites. The applicability of Yoon–Nelson and Thomas models indicates that the dynamic adsorption is controlled by external and internal diffusion.

To prepare activated carbon with a high specific surface area, oxygen functional groups (OFGs) that can serve as useful electron donors during KOH activation were treated with nitric acid and incorporated into activated carbon. OFGs are incorporated differently according to the surface characteristics of starting materials. Up to 22.46% OFGs are incorporated into wood-based activated carbons (WACs), the C=O, COOH contents was 1.90, 17.05%, respectively. Whereas up to 12.82% OFGs are incorporated into coconut shell-based activated carbons, the C=O, COOH contents was 4.12, 6.15%, respectively. The OFGs used for increasing the specific surface area are the carbonyl group, and as the content of the functional group increases, the carbonyl group spreads to the carboxyl group. The specific surface area of activated carbons increased by 10–68% with an increase in the carbonyl group up to 6% (maximum point of carbonyl group). On the other hand, the specific surface area for WACs increased when the carboxyl group was 10% or below, but decreased by 6–15% when it increased to 10% or excess.

In this study, commercial activated carbons (ACs) were upgraded by different activation methods, and the gases generated during the activations were defined and quantified. The chemical activation commonly applied for upgrading ACs uses complex reactions, involving pyrolysis, physical, and chemical reactions. The ACs based on wood materials were characterized by elemental analysis, N2 physisorption, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption mass spectrometry. The patterns and composition of the generated gases were analyzed by gas chromatography and X-ray diffraction; high-resolution scanning electron microscopy was also used to characterize the activated carbon. The AC was mostly decomposed to CO2 by pyrolysis and physical activation, while CO was mainly detected during chemical activation from the K2CO3 produced by the reactions between CO2 and K2O. The detected amounts of generated gases were differed at various KOH ratios and residence times. The highest surface area obtained in this study was 2000 m2/g at the optimum ratio of AC and KOH (1:2).

Chlorella-derived activated carbon (CDAC) with a high specific surface area and hierarchical pore structure was prepared as a CO2 adsorbent and as a supercapacitor electrode material. During KOH activation of Chlorella-derived carbon, metallic K gas penetrated from the outer walls to the inner cells, and pores formed on the outer frame and the inner surface. Micropores were dominant in CDAC, contributing toward a high specific surface area (> 3500 m2/g) and a hierarchical pore structure owing to the cell walls. Consequently, CDAC exhibited a high CO2 adsorption capacity (13.41 mmol/g at 10 atm and room temperature) and afforded high specific capacitance (142 F/g) and rate capability (retention ratio: 91.5%) in supercapacitors. Compared with woody- and herbaceous-biomass-derived activated carbons, CDAC has a superior specific surface area when the precursors are used without any pretreatment under the same conditions due to their soft components such as lipids and proteins. Furthermore, developing microalgae into high-value-added products is beneficial from both economic and environmental perspectives.

The high theoretical energy density (2600 Wh kg−1) of Lithium-sulfur batteries and the high theoretical capacity of elemental sulfur (1672 mAh g−1) attract significant research attention. However, the poor electrical conductivity of sulfur and the polysulfide shuttle effect are chronic problems resulting in low sulfur utilization and poor cycling stability. In this study, we address these problems by coating a polyethylene separator with a layer of activated carbon powder. A lithium-sulfur cell containing the activated carbon powder-coated separator exhibits an initial specific discharge capacity of 1400 mAh g−1 at 0.1 C, and retains 63% of the initial capacity after 100 cycles at 0.2 C, whereas the equivalent cell with a bare separator exhibits a 1200 mAh g−1 initial specific discharge capacity, and 50% capacity retention under the same conditions. The activated carbon powder-coated separator also enhances the rate capability. These results indicate that the microstructure of the activated carbon powder layer provides space for the sulfur redox reaction and facilitates fast electron transport. Concurrently, the activated carbon powder layer traps and reutilizes any polysulfides dissolved in the electrolyte. The approach presented here provides insights for overcoming the problems associated with lithium-sulfur batteries and promoting their practical use.

Capacitive deionization (CDI) process is an emerging process for water desalination. Recently, there has been a major development of architectures in CDI cells using carbon flow electrodes with membrane, called flow-electrode capacitive deionization (FCDI). In FCDI, the advantage is continuous desalination due to the carbon flow electrodes. Numerous research groups dedicated to develop the FCDI process, however, a clear pre-treatment of carbon flow electrodes was not suggested. Study herein, present a clear understanding of effects of pre-treatment of activated carbon based on sonication in the carbon flow electrodes for the basics results with respect to adsorption performance.

Prussian blue is known as a superior material for selective adsorption of radioactive cesium ions; however, the separation of Prussian blue from aqueous suspension, due to particle size of around several tens of nanometers, is a hurdle that must be overcome. Therefore, this study aims to develop granule type adsorbent material containing Prussian blue in order to selectively adsorb and remove radioactive cesium in water. The surface of granular activated carbon was grafted using a covalent organic polymer (COP-19) in order to enhance Prussian blue immobilization. To maximize the degree of immobilization and minimize subsequent detachment of Prussian blue, several immobilization pathways were evaluated. As a result, the highest cesium adsorption performance was achieved when Prussian blue was synthesized in-situ without solid-liquid separation step during synthesis. The sample obtained under optimal conditions was further analyzed by scanning electron microscope-energy dispersive spectrometry, and it was confirmed that Prussian blue, which is about 9.7% of the total weight, was fixed on the surface of the activated carbon; this level of fixing represented a two-fold improvement compared to before COP-19 modification. In addition, an elution test was carried out to evaluate the stability of Prussian blue. Leaching of Prussian blue and cesium decreased by 1/2 and 1/3, respectively, compared to those levels before modification, showing increased stability due to COP-19 grafting. The Prussian blue based adsorbent material developed in this study is expected to be useful as a decontamination material to mitigate the release of radioactive materials.

본 연구에서는 활성탄소섬유를 이용하여 축전식 탈염공정에 적용할 탄소전극을 제조하였다. polyvinylidene fluoride (PVDF)를 바인더로 사용했으며 적절한 용매에 활성탄소섬유를 배합한 후 상용의 그라파이트 시트에 캐스팅하여 탄소전극을 제조하였다. 이 때 활성탄소섬유의 입자 크기를 달리하였고, 용매, 고분자 바인더 그리고 활성탄소섬유를 80 : 2 : 18, 80 : 5 : 15의 배합비율로 전극을 제조하였다. 그런 다음 염 제거 효율을 흡착전압과 시간, 탈착전압과 시간, NaCl 공급액의 농도와 유속 등에 운전조건에 대하여 염 제거 효율을 측정하였다. 대표적으로 활성탄소섬유의 입자크기가 32 μm 이하이며 80 : 2 : 18의 배합비율에서 1.2 V, 3분의 흡착조건, -0.1 V, 1분의 탈착조건, NaCl 100 mg/L, 15 mL/min의 공급액 조건에서 53.6%의 염 제거 효율을 보였다.

실 산성 도금폐수를 입상활성탄(GAC)이 유동메디아로 첨가된 유동상 멤브레인 반응기를 이용하여 처리하였다. GAC 유동조건에서 적용 투과플럭스에 대해 시간에 따른 흡입압의 증가는 관찰되지 않았다. 폐수의 중성 pH에서 파울링 속도는 산성 조건에 비해 GAC 유동조건에서 크게 감소하였다. 해당 폐수의 용액 pH 증가는 입자크기의 증가를 가져왔고 이는 멤브레인 표면에서 상대적으로 성긴 구조의 케이크층 형성을 야기시켰다. 유동상 멤브레인 반응기에서 GAC 유동 하에 95% 이상의 COD 제거율이 관찰되었으며 총부유물질은 거의 완벽하게 제거되었다. 실 도금폐수의 pH에서, 유동상 멤브레인 반응기의 구리 및 크롬의 제거는 거의 관찰 되지 않았다. 그러나 pH를 중성으로 증가 시켰을 시 구리와 크롬의 제거율은 각각 99%와 94%까지 증가를 하였다. 적용해 준 pH에 상관 없이, 시안의 경우 95% 이상의 제거율을 달성하였다. 이는 유기물과 시안 착물 형성으로 인해 유동상 멤브레인 반응기 내 GAC의 강한 흡착으로 제거된 것으로 사료된다.