PAN基活性炭纤维的表面及其孔隙结构解析

通过氮吸附等温线、X射线光电子能谱以及扫描电子显微镜（SEM）对聚丙烯腈（PAN-Polyacrylonitrile）-基活性炭纤维（ACF-Activated Carbon Fiber）的表面和孔隙结构进行了分析,结果表明吸附测量可以提供有关碳质吸附剂的孔结构复杂性;通过XPS对PAN基ACF的表面官能团的种类及含量进行了表征,由SEM对PAN基ACF的表面以及断面的孔隙结构进行了直接观察,提供了有关孔隙结构的直接证据。     

负载Pt活性炭纤维对NO的吸附活性

 采用电化学方法制备了负载Pt的活性炭纤维，为研究其微孔结构、Pt的分散性以及对NO的吸附活性，分别考察了其对氮气、水和NO的吸附．电沉积Pt活性炭纤维的氮吸附等温线仍呈Langmuir型，表面积和微孔孔径基本不变；对水的初始吸附点数远远大于活性炭纤维．这表明电沉积Pt没有改变活性炭纤维的微孔结构，Pt粒高度分散在活性炭纤维的外表面．而NO的吸附量显著增加，说明存在化学吸附．     

改性活性炭纤维吸附二甲胺水溶液的研究

采用气相氧化法制备改性ACF,以二甲胺水溶液为吸附对象,在静态吸附条件下研究了吸附时间、温度、ACF用量对吸附效果的影响,获得了吸附等温线;在动态吸附条件下测定了动态穿透曲线,并研究了ACF的再生方法。在ACF优化用量0.6g/100mL溶液条件下,对初始浓度256mg/L二甲胺溶液的吸附率为85%;吸附饱和的ACF用5%盐酸溶液进行再生时,再生率接近100%。     

磁性水铁矿的制备及其对二甲基亚胂酸的吸附性能

二甲基亚胂酸会对人体和环境造成严重危害。用水热法合成磁性水铁矿,对产物进行了X射线衍射分析、BET比表面积分析和磁滞回线分析,结果表明磁性水铁矿纯度较高,比表面积较大,具有较强的磁性。用磁性水铁矿作为吸附剂,考察了二甲基亚胂酸在磁性水铁矿上的吸附动力学及吸附等温线。二甲基亚胂酸在磁性水铁矿上的吸附符合准二级动力学模型,吸附速率为0.34g·mg^-1·h^-1;吸附等温线符合Freundlich模型。采用Zeta电位测定、FT-IR、SEM-EDS和XPS对吸附机理进行分析,表明磁性水铁矿通过配位络合作用和静电作用来吸附二甲基亚胂酸,在吸附过程中磁性水铁矿表面形了成Fe-O-As三元络合物。研究结果为含有二甲基亚胂酸污染物的水体处理和净化提供了新方法。     

硫辛酸在3种不同树脂上的吸附热力学和动力学研究

研究了硫辛酸在3种不同树脂上的吸附热力学和动力学。研究结果表明,硫辛酸在NG-16树脂上的吸附等温线符合Langmuir等温吸附方程,是单分子层吸附,吸附过程符合一级动力学吸附方程。硫辛酸在NDA-100和ND-90树脂上的吸附等温线符合Langmuir等温吸附方程,但并不只是单分子层吸附,对于中高浓度(大于400mg/L)的硫辛酸溶液更重要的是微孔填充作用。硫辛酸在NDA-100和ND-90树脂上的吸附过程分为大孔、中孔区的表面吸附和微孔区的微孔填充两个阶段,两个阶段都符合一级动力学吸附方程。     

超临界甲烷在高表面活性炭上的吸附测量及其理论分析

实验测定了0～10 MPa,233～333 K (20 K间隔)范围内超临界甲烷在高表面活性炭上的吸/脱附等温线,确定了此物理吸附过程的可逆性,并从实验数据计算出吸附热为16.5 kJ/mol.　建立了描述具有最大点的吸附等温线模型,其总体偏差为±2%.　模型保持了特征吸附能恒定的性质,方程指数亦反映了吸附剂的微孔分布特征,模型参数给出了超临界甲烷的吸附相密度.　将超临界吸附极限态引入等温线模型中,经典的吸附理论亦可解释超临界吸附现象.     

分子筛型PAN-ACF制备及表面结构的XPS研究

以聚丙烯腈基活性炭纤维（PAN ACF）为原料,首次采用液相浸渍结合空气氧化的方 法,在较为温和的条件下改变原料的表面结构和孔隙结构,制备出具有分离N2/O2性能的分子 筛型PAN ACF.采用TGA DTA、电子天平及XPS技术分析表征了分子筛型PAN ACF的吸附性能 和表面结构.结果表明:浸渍煤焦油后的PAN ACF在100～400 ℃之间失重缓慢,是煤焦油中苯 环及杂环类化合物与纤维表面氧化接枝的过程;经350 ℃浸渍空气氧化ACF对N2/O2吸附量及 选择性均得到了显著提高,选择系数达到5.6;浸渍煤焦油的PAN ACF表面具有一定量的羟基 、醚基、羰基和羧基等含氧官能团,氧化过程中各类官能团含量发生改变,类石墨碳含量随浸 渍浓度增加而增大;浸渍氧化再炭化的结果使PAN ACF对N2/O2吸附选择性得到明显提高.     

活性炭纤维对挥发性有机物的吸附及其等温线的拟合

空气中挥发性有机化合物（VOC）严重危害人的身体健康,因而研究VOC的去除具有重要意义。本文研究了不同比表面积粘胶基活性炭纤维（ACF）对低浓度VOC,丁酮和苯的吸附,并用Freundilch方程和DR方程对吸附等温线进行了拟合。结果表明：当丁酮的浓度高于100ppm时,比表面积高的ACF吸附容量高;当浓度低于100ppm时,情形正好相反。在实验浓度范围,较高比表面积的活性炭纤维对苯的吸附表现出了较高的吸附容量。Freundlich方程和DR方程能很好地拟合吸附等温线。     

新型吸附树脂对苯乙酸的吸附热力学研究

研究了苯乙酸在新型超高交联树脂AH、NDa-150和大孔吸附树脂(Amberlite XAD-4)上的平衡吸附数据，测定了288K、303K和318K温度下的吸附等温线，结果表明吸附过程符合Langmuir吸附等温方程。苯乙酸在AH、NDa-150上的吸附容量分别比在Amberlite XAD-4上的吸附容量最高高出90％、113％，这主要归因于AH、NDa-150表面的极性基团及树脂的微孔结构．Langmuir吸附等温线、相对吸附容量以及等量吸附焓变表明，苯乙酸在AH树脂上的吸附是物理吸附和化学吸附共同作用的结果．对苯乙酸被3种树脂吸附的吸附焓变、自由能变、吸附熵变也作了计算，并对吸附行为作了合理的解释。     

Effect of SO2 and NO on removal of VOC from simulated flue gas by activated carbon fibers at low temperature

采用H2O2浸渍的方法对活性炭纤维(ACF)进行改性,并利用氮吸附等温线和XPS(X-ray photoelectron spectroscopy)的方法对ACF样品进行表征.通过实验测定改性前后ACF脱除VOC(甲苯作为VOC的代表物)的效果,同时考察二氧化硫( SO2)和一氧化氮(NO)对ACF脱除甲苯的影响.研究发现,双氧水浸渍改性对ACF的BET表面积和孔容没有影响,但使得ACF样品表面的含氧官能团含量大量增加.实验数据也表明,SO2和NO对VOC在ACF上的吸附具有抑制作用,且随着两者浓度的增加,抑制作用也增强.研究还发现,SO2和NO同时存在比单一的SO2或NO对VOC在ACF上吸附的抑制作用更为明显.     

Nitrogen adsorption on fluorinated activated carbon fiber

Nitrogen adsorption isotherms for fluorinated activated carbon fiber (F-ACF) and fluorinated carbon black (F-CB) were measured at 77 K. Surface structures of F-ACF and F-CB were examined by _s -plot analysis using the adsorption data on the nonporous carbon black (CB) and F-CB. The surface energy of F-ACF was lower than that of ACF. The micropore structure of ACF was preserved even after fluorination, although the limiting adsorption amount and the micropore width decreased with fluorination.     

Study of Water Adsorption on Activated Carbons with Different Degrees of Surface Oxidation

A carbon of wood origin was oxidized with different oxidizing agents (nitric acid, hydrogen peroxide, and ammonium persulfate). The microstructural properties of the starting material and the oxidized samples were characterized using sorption of nitrogen. The surface acidity was determined using Boehm titration and potentiometric titration. The changes in the surface chemistry were also studied by diffuse reflectance FTIR. Water adsorption isotherms were measured at three different temperatures close to ambient (relative pressure from 0.001 to 0.3). From the isotherms the heats of adsorption were calculated using a virial equation. The results indicated that the isosteric heats of water adsorption are affected by the surface heterogeneity only at low surface coverage. In all cases the limiting heat of adsorption was equal to the heat of water condensation (45 kJ/mol).     

Water vapor adsorption and microporous structure of carbon adsorbents. 17. Analysis of experimental isotherms for water vapor adsorption

Water vapor adsorption for various activated carbons with narrow and wide micropore volume distributions and mesopore surface areas between 40 and 300 m²/g have been investigated. For all the isotherms the point of inflection was determined, which can be taken as the point characterizing the formation of a water adsorption layer on the pore wall surface of carbon adsorbents. To do this the adsorption and desorption branches of the isotherms were approximated according to Weibull's distribution. A good correlation was obtained between values for the water monolayer capacity, calculated from the porous structure parameters of the carbons, and the adsorption values corresponding to the isotherm inflection pointsa _inf. For the group of carbons studied the values of relative pressure at the inflection point of the isotherms fell within the range 0.5–0.72.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 31–34, January, 1991.     

Activated carbon oxygen content influence on water and surfactant adsorption

This research investigates the adsorption properties of three activated carbons (AC) derived from coconut, coal, and wood origin. Each carbon demonstrates different levels of resistance to 2 M NaOH treatment. The coconut AC offers the greatest and wood AC the least resistance. The influence of base treatment is mapped in terms of its effects on specific surface area, micropore volume, water adsorption, and dodecanoic acid adsorption from both water and 2 M NaOH solution. A linear relationship exists between the number of water molecules adsorbed at the B-point of the water adsorption isotherm and the oxygen content determined from elemental analysis. Surfactant adsorption isotherms from water and 2 M NaOH indicate that the AC oxygen content effects a greater dependence on affinity for surfactant than specific surface area and micropore volume. We show a linear relationship between the plateau amount of surfactant adsorbed and the AC oxygen content in both water and NaOH phases. The higher the AC oxygen content, the lower the amount of surfactant adsorbed. In contrast, no obvious relationship could be drawn between the surfactant amount adsorbed and the surface area.     

Benzene and toluene adsorption at low concentration on activated carbon fibres

The present study analyses the preparation of activated carbon fibres (ACFs) by the so-called “physical” activation method with steam or carbon dioxide and their application for benzene and toluene adsorption at low concentration (200 ppmv). ACFs have been scarcely studied for the adsorption of these pollutants at low concentration in gaseous phase, despite their interesting features regarding adsorption kinetics, bed pressure drop, possibility of conformation and others. Our results have shown that the preparation method used is suitable to produce ACFs with high adsorption capacities for benzene and toluene at the low concentration used. The fibre morphology of the ACFs does not enhance their performance, which results to be similar to other non-fibrous activated carbons such as granular, pellets and powders. Such good performance of the ACFs, leading to benzene and toluene adsorption capacities as large as 31 g benzene/100 g ACF or 53 g toluene/100 g ACF, can be explained due to their large volume of narrow micropores (<0.7 nm) developed upon activation and their low content in surface oxygen groups. Our results have also shown very good agreement between the adsorption results derived from dynamic adsorption experiments and from adsorption isotherms. As the relative pressure of the organic compound increases the corresponding fraction of narrow micropore volumes filled by benzene and toluene increases. For a given low and comparable relative pressure, toluene always occupies a larger fraction of narrow micropores than benzene.     

Micropore filling of NO,SO2, NH3, and CO2 onα-FeOOH dispersed activated carbon fibers

Adsorption isotherms of NO, SO₂, NH₃, and CO₂ on-FeOOH dispersed activated carbon fibers at 303 K were examined to determine the role of surface modification in micropore filling. The parameters on micropore structures were obtained from both nitrogen adsorption at 77 K and benzene adsorption at 303 K; both isotherms were of BDDTI type and gave the same micropore volume. The preoxidation conditions of ACF, prior to the deposition of-FeOOH against the NO adsorptivity were examined. The dispersion of-FeOOH on ACF was effective in enhancement of micropore filling, irrespective of the adsorbate molecule. We determined the degree of volume filling for each gas by the use of a DR plot. The modified DR plot for an NO gas, of which the critical temperature was much lower than 303 K, was proposed. The degree of volume filling for various gases was correlated with the deviation of each boiling point from 303 K and with the van der Waalsa constant.     

Hydrogen adsorption on functionalized nanoporous activated carbons

There is considerable interest in hydrogen adsorption on carbon nanotubes and porous carbons as a method of storage for transport and related energy applications. This investigation has involved a systematic investigation of the role of functional groups and porous structure characteristics in determining the hydrogen adsorption characteristics of porous carbons. Suites of carbons were prepared with a wide range of nitrogen and oxygen contents and types of functional groups to investigate their effect on hydrogen adsorption. The porous structures of the carbons were characterized by nitrogen (77 K) and carbon dioxide (273 K) adsorption methods. Hydrogen adsorption isotherms were studied at 77 K and pressure up to 100 kPa. All the isotherms were Type I in the IUPAC classification scheme. Hydrogen isobars indicated that the adsorption of hydrogen is very temperature dependent with little or no hydrogen adsorption above 195 K. The isosteric enthalpies of adsorption at zero surface coverage were obtained using a virial equation, while the values at various surface coverages were obtained from the van't Hoff isochore. The values were in the range 3.9-5.2 kJ mol(-1) for the carbons studied. The thermodynamics of the adsorption process are discussed in relation to temperature limitations for hydrogen storage applications. The maximum amounts of hydrogen adsorbed correlated with the micropore volume obtained from extrapolation of the Dubinin-Radushkevich equation for carbon dioxide adsorption. Functional groups have a small detrimental effect on hydrogen adsorption, and this is related to decreased adsorbate-adsorbent and increased adsorbate-adsorbate interactions.     

Synthesis and Characterization of Microporous Silica Prepared with Sodium Silicate and Organosilane Compounds

Microporous silica gels were prepared in the pH range of 3–4 using sodium silicate as a silica source. Surface polarity of these gels was modified by grafting hydrophobic groups into the silica gel matrix with the help of hydrophilic solvents (acetone, acetonitrile, ethanol and methanol) and alkoxysilane compounds containing nonhydrolyzable alkyl groups. The porous framework and hydrophobicity of the silica gels were evaluated using nitrogen adsorption/desorption and water adsorption measurement techniques. All the measured isotherms were found to be type I which is indicative of microporosity. The surface area and microporosity of these samples were estimated by analyzing the measured nitrogen adsorption/desorption data using BET, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The micropore size distribution was determined from their nitrogen adsorption isotherms using the slit-pore model of the Horvath-Kawazoe equation. Silica gels with high surface area (over 500 m²/g) as well as high microporosity (over 0.2 cc/g) were obtained at gelation pH of 3.50 from the water-solvent system.     

Preparation and characterization of activated carbon fibers supported with silver metal for antibacterial behavior

In this work, the effect of immersion in silver nitrate solution on activated carbon fibers (ACFs) was investigated in relation to adsorption behavior and antibacterial activity of ACFs supported with silver (ACF/Ag). The pore and surface properties were studied in terms of BET volumetric measurement with nitrogen adsorption, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The antibacterial activities of ACF/Ag were studied in broth dilution tests against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) from a point of view of water purification. As an experimental result, the silver content of ACF/Ag increased with increasing concentration of silver nitrate. It was found that the micropore structure slightly decreased as the silver nitrate concentration increased. Otherwise, it was revealed that the ACF/Ag possessed a strong antibacterial activity and an inhibitory effect for the growing of E. coli and S. aureus, respectively. Silver content on ACF/Ag decreased rapidly because of rough morphology of silver particles in water erosion.