不同结构活性炭对甲苯的吸附性能

考察了不同结构的活性炭样品对高浓度和低浓度甲苯蒸汽的吸附行为,采用低温(77 K)氮气吸附和129Xe-核磁共振方法对所用活性炭的结构进行了表征.并将活性炭对甲苯的吸附性能与其结构进行了关联.结果表明孔容积大的活性炭对高浓度甲苯蒸汽吸附容量大,而具有丰富微孔和较小平均孔径的活性炭对低浓度(2×10-5)甲苯蒸汽具有高的吸附容量.沥青基活性炭纤维对低浓度(2×10-5)甲苯蒸汽表现出较好的吸附能力.随着比表面积的增大,活性炭纤维对低浓度(2×10-5)甲苯蒸汽的吸附容量略有增加.OG5A,OG10A,OG15A和OG20A在30 ℃下对2×10-5甲苯蒸汽的饱和吸附容量分别为202 mg/g,219 mg/g,221 mg/g和235 mg/g.     

Enhanced hydrogen storage capacity of nanosized copper loaded active carbons treated under CO2

A kind of composites with nanosized Cu loaded on activated active carbons was prepared. The materials were characterized by X-ray diffraction (XRD) patterns, transmission electron microscope (TEM) and nitrogen adsorption. The highest surface area of 2746 m2/g was obtained for the optimized activated active carbon. TEM image and size distribution analyses show that the ball-like Cu(0) particles are dispersed homogeneously in the composites with diameters of 10-30 nm. The electrochemical hydrogen storage properties were determined and an optimized discharge capacity of 605.5 mAh/g was gotten, which corresponds to 2.24 wt% of hydrogen uptake capacity.     

Adsorption characteristics of acetone, chloroform and acetonitrile on sludge-derived adsorbent, commercial granular activated carbon and activated carbon fibers

The adsorption characteristics of chloroform, acetone, and acetonitrile on commercial activated carbon (C1), two types of activated carbon fibers (F1 and F2), and sludge adsorbent (S1) was investigated. The chloroform influent concentration ranged from 90 to 7800 ppm and the acetone concentration from 80 to 6900 ppm; the sequence of the adsorption capacity of chloroform and acetone on adsorbents was F2>F1 approximately C1 approximately S1. The adsorption capacity of acetonitrile ranged from 4 to 100 mg/g, corresponding to the influent range from 43 to 2700 ppm for C1, S1, and F1. The acetonitrile adsorption capacity of F2 was approximately 20% higher than that of the other adsorbents at temperatures<30 degrees C. The Freundlich equation fit the data better than the Langmuir and Dubinin-Radushkevich (D-R) equations. The adsorption rate of carbon fibers is higher than that of the other adsorbents due to their smaller fiber diameter and higher surface area. The micropore diffusion coefficient of VOC on activated carbon and sludge adsorbent was approximately 10(-4) cm2 s(-1). The diffusion coefficient of VOC on carbon fibers ranged from 10(-8) to 10(-7) cm2 s(-1). The small carbon fiber pore size corresponds to a smaller diffusion coefficient.     

Synthesis of ordered large-pore mesoporous carbon for Cr(VI) adsorption

Highly ordered mesoporous carbon with large accessible pores (OMC-P) was prepared by using laboratory-made poly(ethylene oxide)-b-polystyrene diblock copolymer as template via the evaporation-induced self-assembly method. The OMC-P was first used as adsorbent for removal of Cr(VI) ion from aqueous solution. Adsorption behavior was studied as a function of time, concentration of adsorbate, temperature, and pH. The kinetics of adsorption of Cr(VI) ion onto OMC-P is well fit to the pseudo-second order model. The Cr(VI) ion adsorption is favored at lower temperatures and at initial acid pH values in the equilibrium. The Freundlich and the Langmuir isotherm fit the equilibrium data satisfactorily. The influence of porosity on equilibrium adsorption capacity was investigated on three types of carbon materials, namely, OMC-P, ordered mesoporous carbon templated from amphiphilic triblock copolymer F127 (OMC-F) and commercial activated carbon (AC). The prepared OMC-P exhibits much higher adsorption performance than the other two carbons.     

活性炭的双氧水表面改性及其吸附二氧化硫性能研究

目的 制备武器装备贮存微环境用单组分的二氧化硫吸附材料。方法 采用双氧水对椰壳活性炭进行表面改性,研究改性活性炭孔隙结构、表面化学性质的变化及其对二氧化硫吸附性能的影响。结果 活性炭存在微孔和中孔,改性后活性炭比表面积略有增加,平均孔径减小。双氧水与活性炭反应起到刻蚀作用,在活性炭表面产生了纳米尺度的网孔结构,降低了活性炭表面碳微晶有序程度,同时双氧水与活性炭反应时起到了氧化作用,提升了活性炭表面氧元素和含氧官能团含量。体积分数为20%的双氧水改性活性炭的吸附容量最高,达到154.15 mg/g,约为改性前的5倍。结论 双氧水对活性炭经表面改性后,产生了纳米尺度的孔隙,并提升了活性炭表面含氧官能团,在两者协同作用下显著提升活性炭对SO₂吸附性能,具有良好的装备应用前景。     

Liquid phase adsorption of selected chloroaromatic compounds over metal organic frameworks

The adsorption behavior of selected chloroaromatic compounds (chlorobenzene, 2-chlorotoluene, 1,3-dichlorobenzene, and 2-chloroanisole) over metal organic frameworks (MOFs) of MIL-125, NH₂-MIL-125, UiO-66, MIL-101, and Cu₃(BTC)₂ were investigated. NH₂-MIL-125 showed the highest adsorption capacity at 0.1 M, whereas MIL-101 showed the highest adsorption at 1.0 M, which was significantly higher than that of activated carbon under the given conditions. The equilibrium adsorption and kinetics data could be fitted well by the Langmuir model and pseudo-second-order kinetic model, respectively. The adsorption of 2-chloroanisole over NH₂-MIL-125, MIL-101, and activated carbon was spontaneous and exothermic, and the randomness increased after adsorption. The adsorption rate constants increased with temperature and showed a dependence on the pore window size and surface functionality of the MOFs. NH₂-MIL-125 and MIL-101 showed a preference for 2-chloroanisole in a mixture with other chloroaromatic compounds. The surface area and microporosity of the MOFs appear to be major factors governing the adsorption capacity of 2-chloroanisole.     

Effect of preparation conditions on the hydrogen storage capacity of activated carbon adsorbents with super-high specific surface areas

A series of activated carbon adsorbents with super-high specific surface areas (SHAC) (S_BET ≥ 2500 m² g⁻¹) was prepared and used to adsorb storage hydrogen. The results indicated that the structure of activated carbon adsorbents and hydrogen storage capacity are affected by preparation conditions. The influence of preparation conditions on hydrogen storage capacity can be attributed to changes in the structure of the prepared activated carbon adsorbents. The prepared adsorbents had high hydrogen storage capacity, reaching 5.65 wt % and 4.98 wt % when the adsorption temperatures were 0 °C and 25 °C, respectively, and the pressure was 9.0 MPa.     

Electrospun polyurethane fibers for absorption of volatile organic compounds from air

Electrospun polyurethane fibers for removal of volatile organic compounds (VOC) from air with rapid VOC absorption and desorption have been developed. Polyurethanes based on 4,4-methylenebis(phenylisocyanate) (MDI) and aliphatic isophorone diisocyanate as the hard segments and butanediol and tetramethylene glycol as the soft segments were electrospun from their solutions in N,N-dimethylformamide to form micrometer-sized fibers. Although activated carbon possessed a many-fold higher surface area than the polyurethane fiber meshes, the sorption capacity of the polyurethane fibers was found to be similar to that of activated carbon specifically designed for vapor adsorption. Furthermore, in contrast to VOC sorption on activated carbon, where complete regeneration of the adsorbent was not possible, the polyurethane fibers demonstrated a completely reversible absorption and desorption, with desorption obtained by a simple purging with nitrogen at room temperature. The fibers possessed a high affinity toward toluene and chloroform, but aliphatic hexane lacked the necessary strong attractive interactions with the polyurethane chains and therefore was less strongly absorbed. The selectivity of the polyurethane fibers toward different vapors, along with the ease of regeneration, makes them attractive materials for VOC filtration.     

压电材料对含铂活性炭氢气吸附性能的影响

用机械混合法制备含有不同质量分数铂的活性炭,研究了压电材料PMN-PT产生的电荷对含铂活性炭氢气吸附性能的影响。结果表明,在高压氢气条件下PMN-PT产生的电荷能增强铂和活性炭颗粒对氢气分子的吸附,并加速氢气分子的解离和氢原子的扩散,使含铂活性炭的储氢量明显提高。铂产生的氢溢流作用有效地提高了活性炭的氢气吸附量。在室温和8 MPa氢气压力条件下PMN-PT使活性炭(NAC)氢气吸附量产生的增长幅度为15%,使含有质量分数0.83%、1%和1.25%铂的活性炭氢气吸附量增长的幅度分别为36.5%、39.3%和43.9%。     

表面改性对活性炭孔结构及热电转换性能的影响

为探究表面改性对活性炭孔结构及热电转换性能的影响,使用HNO_3和KOH在不同条件下对活性炭进行表面改性,用N2吸附法和XRD图谱表征活性炭改性前后孔结构和石墨化程度的变化。结果表明,改性后活性炭的比表面积和孔容提高,平均孔径减小,并存在石墨晶体结构。干法改性活性炭的比表面积和总孔容由1 077.880m~2/g和0.763cm~3/g分别增加到1 635.268m~2/g和1.128cm~3/g,并且微孔的孔容增加。改性处理可以去除活性炭中的杂质。分别以改性前后活性炭为材料制备固体电极,KCl为电解液,测试活性炭电极的热电转换性能,发现改性后活性炭具有更高的热电转换性能。     

Nanoporous Polymers for Hydrogen Storage

The design of hydrogen storage materials is one of the principal challenges that must be met before the development of a hydrogen economy. While hydrogen has a large specific energy, its volumetric energy density is so low as to require development of materials that can store and release it when needed. While much of the research on hydrogen storage focuses on metal hydrides, these materials are currently limited by slow kinetics and energy inefficiency. Nanostructured materials with high surface areas are actively being developed as another option. These materials avoid some of the kinetic and thermodynamic drawbacks of metal hydrides and other reactive methods of storing hydrogen. In this work, progress towards hydrogen storage with nanoporous materials in general and porous organic polymers in particular is critically reviewed. Mechanisms of formation for crosslinked polymers, hypercrosslinked polymers, polymers of intrinsic microporosity, and covalent organic frameworks are discussed. Strategies for controlling hydrogen storage capacity and adsorption enthalpy via manipulation of surface area, pore size, and pore volume are discussed in detail.

     

Optimization of the Pore Structures of MOFs for Record High Hydrogen Volumetric Working Capacity

Metal–organic frameworks (MOFs) are promising materials for onboard hydrogen storage thanks to the tunable pore size, pore volume, and pore geometry. In consideration of pore structures, the correlation between the pore volume and hydrogen storage capacity is examined and two empirical equations are rationalized to predict the hydrogen storage capacity of MOFs with different pore geometries. The total hydrogen adsorption under 100 bar and 77 K is predicted as n_tot= 0.085× V_p − 0.013× V_p² for cage-type MOFs and n_tot= 0.076× V_p − 0.011× V_p² for channel-type MOFs, where V_p is the pore volume of corresponding MOFs. The predictions by these empirical equations are validated by several MOFs with an average deviation of 5.4%. Compared with a previous equation for activated carbon materials, the empirical equations demonstrate superior accuracy especially for MOFs with high surface area (i.e., S_BET over ≈3000 m² g⁻¹). Guided by these empirical equations, a highly porous Zr-MOF NPF-200 (NPF: Nebraska Porous Framework) is examined to possess outstanding hydrogen total adsorption capacity (65.7 mmol g⁻¹) at 77 K and record high volumetric working capacity of 37.2 g L⁻¹ between 100 and 5 bar at 77 K.     

蔗渣活性炭二次活化制备及其吸附CO2性能研究

以蔗渣为原料, 以ZnCl₂为活化剂制备出活性炭AC, 并用KOH对活性炭AC进行二次活化制备活性炭KAC。用热重法测定材料的CO₂吸附脱附性能, 傅里叶红外光谱、氮气物理吸附-脱附和扫描电镜对样品进行表征。结果表明：KAC具有优异的CO₂吸附性能, 在60℃下其对CO₂吸附量可达3.45 mmol/g, 而AC的CO₂吸附量仅有1.79 mmol/g。KAC的CO₂吸附能力明显优于AC。循环吸附脱附的结果表明, 经过5次吸附-脱附, 材料的吸附量无显著变化, 表明材料具有良好的再生性能。傅里叶红外分析结果表明两种活性炭材料的特征峰基本一致, 活性炭表面官能团中羟基和羧基可以使活性炭表面的极性增大。氮气物理吸附-脱附和扫描电镜结果表明材料都具有发达的孔径结构, 但KAC的孔径结构比AC更发达, 因此其对CO₂的吸附能力也更强。     

不同碳源多孔碳纤维制备及其吸附性能

先用静电纺丝法制备聚丙烯腈(PAN)、聚乙烯醇(PVA)和聚乙烯吡咯烷酮(PVP)基高分子纤维,然后将其碳化制备出不同碳源的多孔碳纤维材料。使用X-射线衍射仪、红外光谱仪、差示扫描量热仪和N₂吸脱附分析仪等手段表征了碳纤维材料的结构和性能。结果表明,PAN基碳纤维的比表面积最大(113.5 m²/g)、微孔较多,对刚果红的吸附量最大(560.2 g/kg)。根据吸附动力学模型和吸附等温线的分析结果,碳纤维对刚果红的吸附属单层吸附。结果还表明,温度越高材料的吸附速率越高但是吸附量没有明显的变化;在酸性条件下PVA基碳纤维保持较高的吸附活性,而PAN基碳纤维则与之相反;刚果红水溶液的pH值对PVP基碳纤维吸附活性的影响很小。     

功能化纤维素:PET纤维沸石分子筛复合材料对神经毒剂的解毒性研究(英文)

Presently activated carbon is used as an adsorptive material for chemical and biological warfare agents. It possess excellent surface properties such as large surface area, fire-resistance and plenty availability, but has disadvantages such as its heavy weight, low breathability (after adsorption of moisture) and disposal. In this paper, we propose to utilize novel electrospun polymeric nanostructures having zeolites as catalyst materials. In this respective, the electrospun polymer nanofibers would serve as the best possible substitutes to activated carbon based protective clothing applications. This is the first in the literature that reports the integration of these types of catalysts with nanofiberous membranes. Electrospinning of cellulose/polyethylene terephthalate (PET) blend nanofibers has been carried out. Zeolite catalysts (Linde Type A and Mordenite) for the detoxification of nerve agent stimulant-paraoxon, were prepared due to their relative simplicity of synthesis. The catalysts were then coated onto nanofiber membranes and their morphology was confirmed using SEM. This is the first report on the coating of nanofibers with zeolites and their successful demonstration against nerve agent stimulant. The UV absorption spectra clearly show the detoxification ability of the functionalized fibers and their potential to be used in textiles for protection and decontamination.     

Hydrogen storage studies of palladium decorated nitrogen doped graphene nanoplatelets

Hydrogen storage in materials is of significant importance in the present scenario of depleting conventional energy sources. Porous solids such as activated carbon or nanostructured carbon materials have promising future as hydrogen storage media. The hydrogen storage capacity in nanostructured carbon materials can be further enhanced by atomic hydrogen spillover from a supported catalyst. In the present work, the hydrogen storage properties of nitrogen doped graphene nanoplatelets (N-GNP) and palladium decorated nitrogen doped graphene nanoplatelets (Pd/N-GNP) have been investigated. The results show that hydrogen uptake capacity of nitrogen doped graphene nanoplatelets and palladium decorated nitrogen doped graphene nanoplatelets at pressure 32 bar and temperature 25 degrees C is 0.42 wt% and 1.25 wt% respectively. The dispersion of palladium nanoparticles increases the hydrogen storage capacity of nitrogen doped graphene nanoplatelets by 0.83 wt%. This may be due to high dispersion of palladium nanoparticles and strong adhesion between metal and graphene nanoplatelets over the surface of N-GNP, which enhances the spillover mechanism. Thus, an increase in the hydrogen spillover effect and the binding energy between metal nanoparticles and supporting material achieved by nitrogen doping has been observed to result in a higher hydrogen storage capacity of pristine GNP.     

Mesoporous carbon spheres produced by hydrothermal carbonization from rice husk: Optimization,characterization and hydrogen storage

In this study, carbon spheres were synthesized from rice husk with hydrothermal carbonization method at different temperatures and different reaction times. Surface areas and pore size distributions of carbon spheres were characterized by BET surface area device, sphere morphology by SEM, structural characterization by FTIR-ATR and XRD, and thermal properties and degradation mechanism by DTA/TG. In addition, hydrogen gas adsorption measurements of the samples were also carried out with the Hiden IMI PSI gas storage device. It can be said that the required temperature is 280 °C and the required reaction time is 6 h in order to obtain homogeneous and ideal sphere morphology carbon spheres from a lignocellulosic biomass in experiments carried out under different conditions in an acidic reaction medium. This is clearly seen from the SEM images. In addition, FTIR spectra and XRD patterns confirm that the sphere was obtained. According to the BET surface area and pore size distribution results, it can be said that the main significant difference is in the mesopore structure of the carbon spheres, even if the surface area values of the samples obtained at different temperatures and different reaction times increase linearly with temperature. In order to determine the usability of carbon spheres obtained in different conditions in the energy field, the gravimetrically measured H₂ storage capacities at cryogenic temperature (77 K) and pressure range of 0–30 bar were determined as maximum 1.1% by weight. When the hydrogen storage capacities of the samples are evaluated together with the BET surface area values and pore size distributions, it shows that the hydrogen storage capacity in carbon spheres is directly proportional to the mesopore volumes. In addition, Langmuir and Freundlich isotherms related to adsorption equilibrium were investigated in order to better define the H₂ adsorption that took place in these samples. Considering the regression coefficients of the obtained isotherms, it was determined that some of the carbon spheres were more compatible with the Langmuir isotherm and some with the Freundlich isotherm.     

碳质储氢材料的研究进展

碳质材料由于具备质量轻、吸氢量大等优良特性,近年来引起了学者们的广泛关注。综述了碳质储氢材料的研究进展,介绍了碳质材料的储氢机理,并就近年来研究的热点探讨了影响碳质材料储氢的各种因素。最后,对碳质储氢材料的发展前景进行了展望。     

Comparative experimental study of methane adsorption on multi-walled carbon nanotubes and granular activated carbons

In this study, methane storage capacity of granular activated carbons (GACs) and two types of multi-walled carbon nanotubes (MWCNTs) was investigated and compared. An experimental apparatus consisting a dual adsorption vessel was set up for measurement of equilibrium adsorption of methane on adsorbents using volumetric technique at pressure range of 0–50?bar at different temperatures. The first type of MWCNs has shown lower methane uptake (4.5?mmol?g^?1) compared to GACs (6.5?mmol?g^?1) at the temperature of 283.15?K and the pressure of 50?bar, while 33?mmol?g^?1 of methane storage capacity was achieved using the second type of MWCNTs that is much higher than methane storage on GACs at the same operating conditions. The superior uptake performance for the second type of MWCNTs can be attributed to its specific characteristics such as smaller pore size and higher pore volume. The experimental data of adsorption were almost equally well described by Langmuir, Freundlich and Sips equations to determine the model isotherms. The isosteric heat of methane adsorption on the adsorbent was calculated based on Clausius–Clapeyron and the Sips isotherm model using the experimental data at different temperatures. Results revealed that the isosteric heat of methane adsorption on MWCNTs was lower than the heat of methane adsorption on GACs. Low values obtained for isosteric heats of adsorption indicated dominance of physisorption mechanism for all adsorbents. In general, the obtained data indicated that some well-structured MWCNTs with uniform and narrow size distribution as well as higher pore volume are potential materials for methane storage and deserve further study.     

Chromium(VI) adsorption from aqueous solution by Hevea Brasilinesis sawdust activated carbon

Adsorption capacity of Cr(VI) onto Hevea Brasilinesis (Rubber wood) sawdust activated carbon was investigated in a batch system by considering the effects of various parameters like contact time, initial concentration, pH and temperature. Cr(VI) removal is pH dependent and found to be maximum at pH 2.0. Increases in adsorption capacity with increase in temperature indicate that the adsorption reaction is endothermic. Based on this study, the thermodynamic parameters like standard Gibb's free energy (DeltaG degrees ), standard enthalpy (DeltaH degrees ) and standard entropy (DeltaS degrees ) were evaluated. Adsorption kinetics of Cr(VI) ions onto rubber wood sawdust activated carbon were analyzed by pseudo first-order and pseudo second-order models. Pseudo second-order model was found to explain the kinetics of Cr(VI) adsorption most effectively. Intraparticle diffusion studies at different temperatures show that the mechanism of adsorption is mainly dependent on diffusion. The rate of intraparticle diffusion, film diffusion coefficient and pore diffusion coefficient at various temperatures were evaluated. The Langmuir, Freundlich and Temkin isotherm were used to describe the adsorption equilibrium studies of rubber wood sawdust activated carbon at different temperatures. Langmuir isotherm shows better fit than Freundlich and Temkin isotherm in the temperature range studied. The result shows that the rubber wood sawdust activated carbon can be efficiently used for the treatment of wastewaters containing chromium as a low cost alternative compared to commercial activated carbon and other adsorbents reported.