Hydrogenolysis of sorbitol to glycols over carbon nanofiber supported ruthenium catalyst

Sorbitol hydrogenolysis was carried out over a carbon nanofiber supported ruthenium catalyst prepared by incipient wetness impregnation. The carbon nanofiber supported ruthenium catalyst was shown to have an attracting behavior when compared with a commercial activated carbon supported ruthenium catalyst, especially in terms of selectivity to glycols. The preferable hydrogen partial pressure for sorbitol hydrogenolysis was ca. 8.0 MPa, lower than that usually reported in previous works. Slightly soluble calcium hydroxide, which was used as a basic promoter, remarkably increased the selectivity to glycols, as compared with the soluble sodium hydroxide. The variation of product selectivity with catalyst amount indicated that glycerol was the initial C3 polyol product while propylene glycol was derived from glycerol. The parametric investigation was further focused on the intrinsic features of sorbitol hydrogenolysis.     

Fabrication and characterization of polyaniline coated carbon nanofiber for supercapacitor

Polyaniline coated carbon nanofiber was fabricated using one-step vapor deposition polymerization technique. Fourier transform infrared (FT-IR) spectra and transmission electron microscope (TEM) images indicated that uniform and ultrathin conducting polymer layers were formed on the carbon nanofiber surfaces regardless of the coating thickness. It was also confirmed that the thickness of polyaniline layer could be conveniently tuned by the feeding amount of monomer. The coating thickness was dependent on initiator/monomer ratio, the vacuum pressure of reaction chamber and polymerization temperature. Among them, the vacuum pressure was a major factor to control the coating thickness of polyaniline onto the carbon nanofiber surface. In addition, the electrochemical analysis demonstrated that polyaniline coated carbon nanofiber showed an improved performance as supercapacitor. The specific capacitance of polyaniline coated carbon nanofiber exhibited a maximum value of 264 F/g when the thickness of polyaniline layer was ca. 20 nm.     

改性活性炭吸附甲醛的影响因素研究

利用浸渍法制备出以柱状活性炭为基材负载高锰酸钾(KMnO4)的复合型甲醛吸附材料,利用比表面积及孔隙度分析测试仪和场发射扫描电子显微镜观察活性炭改性前后的物理结构变化,搭建单通道滤料性能测试实验台研究高锰酸钾负载率、气体相对湿度、重复负载次数对改性活性炭吸附甲醛的性能影响。结果表明,未负载KMnO4的活性炭对甲醛的吸附性能最差,负载率为5%、10%、20%、24%的改性活性炭比未改性活性炭吸附容量增大1.1、3.5、4.5、5.5倍,最佳负载率为24%;KMnO4负载率10%的改性活性炭在相对湿度为20%、50%的情况下比相对湿度80%时,甲醛吸附容量增大1.5、1.3倍。改性活性炭失活后,重复负载KMnO4 1次仍表现出良好的甲醛吸附性能;但重复负载两次后改性活性炭的甲醛吸附性能下降明显。     

Hydrophilic PVA-co-PE nanofiber membrane functionalized with iminodiacetic acid by solid-phase synthesis for heavy metal ions removal

A novel hydrophilic poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofiber membrane for heavy metal ions removal was fabricated by the solid phase synthesis of iminodiacetic acid (IDA) on nanofiber membrane surfaces. The hydrophilic PVA-co-PE nanofiber membranes were activated with cyanuric chloride. The IDA was then covalently linked to the activated PVA-co-PE nanofiber membranes. The chemical structures of activated and functionalized PVA-co-PE nanofiber membranes were confirmed with FTIR–ATR. The morphology of PVA-co-PE nanofiber membranes were characterized with SEM. The increase in the amount of IDA on functionalized PVA-co-PE nanofiber membranes significantly improved the adsorption amount of Cu²⁺. The IDA functionalized PVA-co-PE nanofiber membranes demonstrated excellent adsorption capability of Cu²⁺, Co²⁺, Zn²⁺ and Ni²⁺. The adsorption of above heavy metal ions could be repeatedly regenerated by desorbing the ions adsorbed on nanofiber membranes. The novel IDA functionalized PVA-co-PE nanofiber membranes have great potential in the application of industry and drinking water treatment.     

竹活性炭碘吸附值对甲醛吸附性能影响的研究

考察了竹活性炭不同碘吸附值及吸附时间对甲醛吸附量的影响。结果表明:随着碘吸附值增加,竹活性炭对甲醛吸附能力也增加,在72 h内碘吸附值最高竹活性炭(744.16mg/g)其甲醛吸附能力为碘吸附值最低竹活性炭(126.83 mg/g) 的2.63倍,通过SPSS软件分析得出,竹活性炭碘吸附值与甲醛吸附成正相关,在72 h内以24 h甲醛吸附量为基准,对每隔24 h甲醛吸附增加值进行比较。结果表明竹活性炭碘吸附值越大,吸附时间越长,竹活性炭对甲醛吸附增加值也越大,且两者之间成正相关。进一步以竹活性炭碘吸附值(X₁)和吸附时间(X₂)为变量进行回归分析,得出回归方程:Y=66.215lnX₁+0.973X₂-286.66,相关系数R²为0.948。     

Tailoring the textural properties of activated carbon xerogels by chemical activation with KOH

Resorcinol–formaldehyde xerogels synthesised with different resorcinol/sodium carbonate molar ratios were chemically activated either after drying or after drying and pyrolysis, using potassium hydroxide. It was found that organic (i.e. dried) and carbon (i.e. pyrolysed) xerogels behave differently when subjected to chemical activation. In the case of carbon xerogels, the increase in the microporosity takes place without any significant modification to the meso/macroporosity formed during the synthesis step, leading to micro–mesoporous or micro–macroporous materials with a larger micropore volume. Furthermore, control of the microporosity is possible because its development depends on the amount of KOH used. However, when organic xerogels are activated, mainly microporous materials with BET specific surface areas of up to 2000 m² g⁻¹ are obtained, there hardly remaining any of the meso/macroporosity formed during the gel synthesis. Thus, the combination of different synthesis conditions and chemical activation with potassium hydroxide allows the textural properties of carbon xerogels to be tailored at both micropore and meso/macropore levels.     

Gaseous adsorption of carbon tetrachloride onto carbon nanofiber arrays prepared by template-assisted synthesis

Adsorption of carbon tetrachloride onto aligned carbon nanofiber (CNF) arrays, prepared by a template-assisted synthesis, in vapor phase is conducted in the present study. Porous structure analysis indicated that various pore size distributions of the CNF arrays are found to vary with their tubular sizes. The increasing tubular size is accompanied by a decreasing micropore fraction as well as a vapor-phase adsorption capacity. Freundlich and Dubinin–Radushkevich models were employed to analyze the equilibrium adsorption data. The surface accessibility of CNF arrays, i.e., adsorption capacity per surface area, was found to decrease with the pore size, according to these models. It is suggested on the basis of the present work that the micropore fraction of CNFs plays an important role in determining the adsorption coverage. Both the equilibrium constant and free energy for the vapor-phase adsorption increase with the micropore proportion, indicating that the micropores act as a high-energy site for adsorption of carbon tetrachloride.     

中孔炭材料的制备及吸附性能的研究

以正硅酸乙酯为模板硅源，酚醛树脂为炭前驱体，运用模板法制备了中孔炭材料。并用红外光谱（FT—IR）、扫描电镜（SEM）、低温N2自动吸附、甲醛和VB12饱和吸附等对样品形貌、孔结构和吸附性能进行了研究。结果表明：制备的炭材料孔径集中分布在2-7nm左右，且中孔孔隙率达到74．6％，比表面积达到1012m^2／g；材料对VB12大分子有较好的吸附性能。表明通过控制正硅酸乙酯的水解条件能制备孔径集中的中孔炭材料。     

活性炭表面改性及吸附极性气体

活性炭的微结构和表面化学特性对其吸附性能产生显著影响。概述了通过调整活性炭孔隙结构。引入化学基团，改变其酸碱度和极性，提高其吸附极性分子能力的方法，介绍了炭表面化学结构，分析了炭微结构，表面基团和吸附质性质对吸附过程的影响。对近年来活性炭表面的改性在吸附SO2和VOCs的实验研究进行了讨论。     

Electrospinning and crosslinking of zein nanofiber mats

Electrospinning processing can be applied to fabricate fibrous polymer mats composed of fibers whose diameters range from several microns down to 100 nm or less. In this article, we describe how electrospinning was used to produce zein nanofiber mats and combined with crosslinking to improve the mechanical properties of the as‐spun mats. Aqueous ethanol solutions of zein were electrospun, and nanoparticles, nanofiber mats, or ribbonlike nanofiber mats were obtained. The effects of the electrospinning solvent and zein concentration on the morphology of the as‐spun nanofiber mats were investigated by scanning electron microscopy. The results showed that the morphologies of the electrospun products exhibited a zein‐dependent concentration. Optimizing conditions for zein produced nanofibers with a diameter of about 500 nm with fewer beads or ribbonlike nanofibers with a diameter of approximately 1–6 μm. Zein nanofiber mats were crosslinked by hexamethylene diisocyanate (HDI). The tensile strength of the crosslinked electrospun zein nanofiber mats was increased significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:380–385, 2007     

相对湿度对甲醛在改性活性炭上吸附的影响

This work mainly involves the study of effect of relative humidity on adsorption of formaldehyde on the activated carbons modified with organosilane solution. Modification of activated carbons was carded out by impregnating activated carbon with organosilane/methanol-containing solutions. The breakthrough curves of formaldehyde in the packed beds of original and modified activated carbons were measured, respectively, at relative humidity of 30%, 60%, and 80%. Temperature-programmed desorption （TPD） experiments were used to estimate the activation energy for desorption of formaldehyde from the activated carbon. Results showed that the relative humidity had strongly influence on breakthrough curves of formaldehyde in the packed beds. The higher the relative humidity of gas mixtures through the packed beds was, the smaller the breakthrough time of formaldehyde became. The use of organosilane compounds to modify surfaces of the activated carbon can enhance the interaction between formaldehyde and the surfaces, and as a result, the breakthrough times of formaldehyde in the packed beds of the modified activated carbon were longer than that in the packed bed of the unmodified activated carbon.     

含银PA6纳米纤维的制备及抗菌性能研究

以次磷酸钠还原硝酸银制得银溶胶,按不同比例加入到质量分数为12%的聚己内酰胺(PA6)/甲酸溶液中,通过静电纺丝制备含银PA6纳米纤维毡,分析了纤维的表面形貌和抗菌性能。结果表明:当纤维中银质量分数为0.1%时,PA6纳米纤维对大肠杆菌的抑菌率达95%以上。扫描电镜和原子力显微镜分析表明,含银PA6纳米纤维比PA6纳米纤维平均直径稍粗,直径分布更集中,纤维直径为80～100 nm,但其表面有明显的褶痕,粗细节较多,不如PA6纳米纤维光滑。     

Study of fire retardant behavior of carbon nanotube membranes and carbon nanofiber paper in carbon fiber reinforced epoxy composites

Single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) membranes (buckypaper) and carbon nanofiber (CNF) paper were incorporated onto the surface of epoxy carbon fiber composites, as proposed fire shields. Their flammability behaviors were investigated by a cone calorimeter. SWCNT buckypaper and CNF paper did not show notable improvement on fire retardancy. However, MWCNT buckypaper acted as an effective flame-retardant shield, reducing the peak heat release rate by more than 60% and reducing smoke generation by 50% during combustion. The pore structures of buckypapers and CNF paper were characterized by scanning electron microscopy (SEM), mercury intrusion porosimetry, and N₂ adsorption isotherms. Gas permeability of buckypaper and carbon nanofiber paper was measured. The correlation between buckypaper and CNF paper properties and their fire retardancy was discussed.     

Carbon–silica composites prepared by the precipitation method. Effect of the synthesis parameters on textural characteristics and toluene dynamic adsorption

Three synthesis routes are presented here that leads to carbon?Csilica composites. These were characterized by nitrogen physisorption, by thermogravimetric analysis and by dynamic toluene adsorption test similar to Ashrae standard I45.1. The carbon?Csilica composites possess high microporosity and mesoporosity as well as large surface areas. Furthermore, the control of the microporosity as well as pore size distribution is possible because they depend on the amount of carbon used and of the synthesis route. Following routes I and III a wide micro-mesoporous pore size (1?C32?nm) was obtained where as by route II narrow micro-mesoporous pore size (1?C4?nm) was observed. In addition, pore diameters center in the range of 1.13?C1.17?nm was observed when carbon content was 32 or 45?wt%. The dynamic adsorption of toluene was evaluated for carbon?Csilica composites obtained by three preparation routes at two different carbon contents, 32 and 45?wt% The results showed that a composite with 45?wt% carbon content and obtained via preparation route I gave the highest toluene adsorption capacity (27.6?wt% relative to carbon content). The large uptake capacity of this composite was attributed to the presence of high microporosity volume and a wide (1?C32?nm) bimodal pore system consisting of extensive mesopore channels (2?C32?nm) as well as large surface area. These capacity values of carbon?Csilica composites are by weight relative to carbon content and are competitive to, results obtained for commercial coconut activated carbon (31.1?wt%) and significantly better than a commercial alumina-carbon composite (9.5?wt%) at 0% efficiency.     

Synthesis of a novel carbon nanofiber structure for removal of lead

A new structure of carbon nanofibers was synthesized by chemical vapor deposition method. Kaolin was used as substrate and cyclohexanol and ferrocene as carbon source and catalyst, respectively. The morphology of the product was studied by scanning electron microscopy. Carbon nanofiber was modified with a mixture of nitric acid and sulfuric acid to enhance its adsorption capacity. The presence of functional groups on the treated adsorbent was assessed by FT-IR spectroscopy. The surface activity of the oxidized sample was estimated by Boehm’s titration. The pH_(PZC) of the samples was also measured. The adsorbent was then used for adsorption of Pb²⁺ at different experimental conditions. The optimized capacity of 211mg·g^?1 was obtained. Kinetic and thermodynamic of the reaction were studied. It was concluded that the adsorption process is spontaneous and endothermic. Equilibrium data were well fitted to the Langmuir model and the pseudo-second-order kinetic model described the adsorption process.     

Role of microporosity and surface functionality of activated carbon in methylene blue dye removal from water

Activated carbons have been prepared from jute stick by both chemical and physical activation methods using zinc chloride and steam, respectively. They were characterized by evaluating surface area, iodine number, pore size distribution, and concentration of surface functional groups. The chemically activated carbon largely featured micropore structure, while the physically activated carbon mainly featured macropore structure. The specific surface area of chemically and physically activated carbons was 2,325 and 723 m ² /g, while the iodine number was 2,105 and 815mg/g, respectively. The concentration of surface functional groups was determined by Boehm titration method, which suggested that different types of surface functional groups are randomly distributed on chemical activated carbons, while it is limited for physical activated carbon. The microporosity along with surface functional groups provided a unique property to chemically activated carbon to adsorb Methylene Blue dye to a large extent. The adsorption of dye was also affected by the adsorption parameters such as adsorption time, temperature and pH. Comparatively, higher temperature and pH significantly facilitated dye adsorption on chemically activated carbon.     

Treatment of pollutants in wastewater: Adsorption of methylene blue onto olive-based activated carbon

This study used olive stone-based activated carbon for the removal of methylene blue from wastewater in order to evaluate the adsorption capacity of the carbon. The equilibrium and kinetics of adsorption were examined at 25°, 30°, 35° and 40 °C and several agitation speeds. Type III adsorption isotherms corresponding to physical adsorption in a multilayer system were used for the methylene blue system. The equilibrium data for methylene blue adsorption showed a good fit to the Freundlich equation. The kinetic data was analysed to determine kinetic constants and order of reaction. Kinetics was evaluated by means of an n-order model, showing that the reaction was a first-order reaction. The results indicated that olive stone-based activated carbon could be used as a low-cost alternative to commercial activated carbon for the removal of organic compounds from wastewater. However, due to its microporosity, the application of this type of activated carbon was found to be suitable for molecules smaller than methylene blue.     

Zwitterionic‐polymer‐functionalized poly(vinyl alcohol‐co‐ethylene) nanofiber membrane for resistance to the adsorption of bacteria and protein

A zwitterionic poly(vinyl alcohol‐co‐ethylene) (PVA‐co‐PE) nanofiber membrane for resistance to bacteria and protein adsorption was fabricated by the atom transfer radical polymerization of sulfobetaine methacrylate (SBMA). The PVA‐co‐PE nanofiber membrane was first surface‐activated by α‐bromoisobutyryl bromide, and then, zwitterionic SBMA was initiated to polymerize onto the surface of nanofiber membrane. The chemical structures of the functionalized PVA‐co‐PE nanofiber membranes were confirmed by attenuated total reflectance–Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. The morphologies of the PVA‐co‐PE nanofiber membranes were characterized by scanning electron microscopy. The results show that the poly(sulfobetaine methacrylate) (PSBMA) was successfully grafted onto the PVA‐co‐PE nanofiber membrane, and the surface of the nanofiber membrane was more hydrophilic than that of the pristine membrane. Furthermore, the antibacterial adsorption properties and resistance to protein adsorption of the surface were investigated. This indicated that the PSBMA‐functionalized surface possessed good antibacterial adsorption activity and resistance to nonspecific protein adsorption. Therefore, this study afforded a convenient and promising method for preparing a new kind of soft and nonwoven dressing material with antibacterial adsorption and antifouling properties that has potential use in the medical field. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44169.     

The effect of mechanical grinding on the mesoporosity of steam‐activated palm kernel shell activated carbons

BACKGROUND: Palm kernel shell activated carbon (OPSA) produced by steam gasification at high temperatures generally results in high surface areas of 1146 to 1600 m² g^?1, attributed to the high volume of micropores (0.43 to 0.56 cm³ g^?1). The mesoporosity of naturally occurring activated carbons is observed to increase with decreasing particle size. Mechanical grinding was therefore performed to investigate its effect on the mesoporosity and microporosity of OPSA. RESULTS: Mechanical grinding had a strong effect on mesopore volume and average pore diameter, with an increase in mesopore volume from 47 to 66% as particle size decreases. Interestingly, no significant effect on the micropore fraction was observed in ground OPSA particles. CONCLUSIONS: The mechanically ground OPSA particles possessed dual adsorption capabilities due to the high microporosity and moderate mesoporosity contained in the structures. This results in interesting porosity behaviour of palm kernel shell activated carbons and the potential to provide materials of distinct sorption capacities with minimal treatment. Copyright © 2009 Society of Chemical Industry     

Activated carbon nanofiber anodes for microbial fuel cells

This investigation considers the use of activated carbon nanofiber nonwoven (ACNFN) as a novel anode for microbial fuel cells (MFCs). ACNFN has an ultra-thin, porous interconnected structure with high bioaccessible surface area. Reduced distances from the free surface to the interior maximize use of the available surface area and this, combined with high macroporosity ensures superior performance by decreasing transport limitations. ACNFN was fabricated by pyrolysis of electrospun polyacrylonitrile and subsequent steam activation. Extensive characterization, including surface morphology, material chemistry, surface area, mechanical strength and biofilm adhesion was performed to validate the use of the material as an MFC anode. Preliminary tests in a single chamber MFC showed current densities of 2715 A/m³ which is about 10% greater than the highest maximum obtained so far. Further, this was achieved with a conductivity of only a fifth of that of the corresponding material. The bio-electrochemical performance of ACNFN was also compared to that of commonly-used anodes, carbon cloth and granular activated carbon. Such anode architecture will greatly help mitigate low power density issues which are one of the main factors limiting widespread adoption of MFCs.