活性炭纤维吸附脱除NO过程中NO氧化路径分析

在小型固定床吸附实验台上开展了黏胶基活性炭纤维吸附脱除NO的实验研究。采用H₂O₂溶液浸渍以及热处理方法对活性炭纤维表面进行修饰,以获得表面孔隙结构接近而含氧官能团含量不同的样品;考察样品在惰性氮气气氛、含氧气氛下吸附脱除NO的效果,以及表面含氧含氮官能团的变化规律。探讨了含氧官能团在NO催化氧化过程中的作用及含氧气氛下O₂对于NO转化为NO₂的影响,分析了活性炭纤维表面吸附的NO向NO₂的主要转化途径。结果表明,在氮气气氛下活性炭纤维表面C-O官能团对吸附态的NO起到氧化作用,吸附态NO被C-O官能团氧化生成-NO₂官能团;在含氧气氛下活性炭纤维吸附NO后表面出现-NO₂、-NO₃官能团,通过长时间实验测定三种样品在含氧气氛下对NO吸附的效果,发现三种样品稳定时催化氧化效果一致,表明含氧官能团对初始NO的物理吸附影响较大,而对整个吸附过程影响较小。吸附在活性炭纤维表面上的NO与环境气氛中的游离态O₂发生氧化反应是NO转变为NO₂的主要途径。     

酸处理活性炭催化水合肼还原硝基苯(英文)

以水合肼为还原剂,采用硝酸、盐酸、硫酸及氮气或氢气氛处理的活性炭为催化剂,考察了其催化硝基苯还原反应性能.结果表明,经化学处理后,活性炭表面形成了各种含氧官能团,它们可引发水合肼分解,并影响硝基苯的吸附.活性炭表面形成的含氧官能团越多,其催化硝基苯还原速率越快.其中经盐酸处理的活性炭表面形成的含氧官能团最多,因而表现出最高的硝基苯还原活性.     

硝酸改性活性炭上氧/氮官能团对脱汞性能的促进作用

采用硝酸氧化手段对活性炭进行了表面处理, 并在固定床反应器上测试了其脱除单质汞的性能. 研究表明, 在模拟烟气中硝酸改性活性炭能有效脱除单质汞. 采用元素分析、Brunauer-Emmett-Teller (BET)比表面积、扫描电子显微镜(SEM)、拉曼(Raman)光谱、Boehm滴定、程序升温脱附(TPD)和X射线光电子能谱(XPS)等手段研究了活性炭表面官能团对其脱汞性能的影响. 结果表明: 硝酸氧化处理能同时增加活性炭表面含氧官能团和含氮官能团的含量. 与改性活性炭的物理性质相比, 其化学性质对脱汞性能的影响更大, 单质汞主要被改性活性炭氧化为HgO而去除. 在脱汞反应中, 羰基、酯基和酸酐等含氧官能团可能是活性吸附位点, 反应后这些官能团被还原为羟基或者醚基; 而吡咯等含氮官能团可能是活性催化位点. 此外, 基于上述表征结果提出了硝酸改性活性炭表面官能团的脱汞机制.     

活性炭表面含氧基团对苯酚吸附平衡及动力学的影响

煤基活性炭分别用烧失处理和HNO3氧化处理后得到不同表面性质的活性炭,采用X射线光电子能谱(XPS)、N2吸附、酸碱滴定及零电荷点(pHPZC)对活性炭表面性质及孔结构进行表征,研究了活性炭表面性质对苯酚吸附平衡和吸附动力学影响.经HNO3氧化后,活性炭表面含氧基团显著增加,烧失处理后,表面含氧基团尤其是羧基显著减少.苯酚最大平衡吸附量随活性炭表面含氧基团的增多而减少,吸附速率常数与碳表面含氧基团的量呈正相关,而吸附活化能与活性炭在一定吸附条件下表面所带电荷多少相关.随着活性炭表面含氧基团增多,吸附活化熵增大(负值减小),苯酚在活性炭表面排列的有序性减小.静态吸附与动态吸附实验结果都表明:在含氧基团较少而碱性更强的活性炭上,发生化学吸附的程度更大.     

几种植物基活性炭材料的表面结构与吸附性能比较——(II)表面化学结构与吸附性能研究

用X-射线光电子能谱对3种植物基活性炭材料:椰壳活性炭 (CAC4)、剑麻茎基活性炭(SSAC)和剑麻基活性碳纤维 (SACF) 的表面化学结构进行了表征,并研究和对比了它们的吸附性能,包括对碘、苯酚和亚甲基蓝的液相吸附性能,对有机蒸汽的吸附性能以及对Au3+的还原吸附性能等。结果表明,3个样品表面均含有多种含氧官能团,吸附能力SACF>SSAC> CAC4。样品的吸附性能主要取决于自身孔结构,与其表面化学结构也有密切的关系。     

几种植物基活性炭材料的表面结构与吸附性能比较-(Ⅱ)表面化学结构与吸附性能研究

用X-射线光电子能谱对3种植物基活性炭材料椰壳活性炭(CAC4)、剑麻茎基活性炭(SSAC)和剑麻基活性碳纤维(SACF)的表面化学结构进行了表征,并研究和对比了它们的吸附性能,包括对碘、苯酚和亚甲基蓝的液相吸附性能,对有机蒸汽的吸附性能以及对Au3+的还原吸附性能等.结果表明,3个样品表面均含有多种含氧官能团,吸附能力SACF＞SSAC＞CAC4.样品的吸附性能主要取决于自身孔结构,与其表面化学结构也有密切的关系.     

微孔碳分子筛表面含氧基团对H_2O_2催化分解的动力学影响

多孔碳的表面含氧官能团对其吸附及催化性能的影响受到越来越多的关注[1-2],表面含氧基团对活性炭催化醇脱水[3]、乙苯脱氢[4]、O2还原为过氧化氢[5]、Fe(II)与O2氧化反应[6]已有报道.     

活性炭分离富集技术的应用新进展

对活性炭分离富集技术的应用新进展进行综述。重点评述了活性炭的结构和吸附机理,活性炭对有机物的分离和吸附,活性炭对金属离子的分离和富集,共引用文献３５篇。     

乙烯渣油沥青基活性炭纤维和粘胶基活性炭纤维的表面性质与脱硫活性

研究了在O2和H2O存在下,乙烯渣油沥青基活性炭纤维(ETPACF)和粘胶基活性炭纤维(CelluloseACF)的脱硫活性.结果表明,在比表面积相近的情况下,ETPACF的脱硫活性明显低于CelluloseACF,这可归因于后者具有较强的吸附和催化氧化SO2能力及较大的吸水量,尤其是具有较强的催化氧化SO2的能力,这些能力又与其表面含有含氮官能团以及某些含氧官能团有关,因此ACF的表面官能团对其脱硫活性影响很大.     

改性活性炭对噻吩的吸附性能研究

用过硫酸铵、臭氧对椰壳活性炭和煤基活性炭进行氧化改性,研究了改性活性炭对噻吩的吸附性能,材料结构袁征结果表明,经两种方法氧化处理后,椰壳炭的孔结构基本保持不变,而煤基炭的比表面积和孔容有所增加.Boehm滴定发现氧化后活性炭表面含氧官能团数量增加并由FT-TR图谱得到证实.氧化处理提高了噻吩在活性炭表面的吸附容量与Langmuir和Freundlich两种吸附等温线方程的相关性.采用拟一级、拟二级和粒子内扩散模型速率方程来考察吸附动力学,并计算了这些动力学模型的速率常数,拟二级模型和实验数据之间有较好的相关性.同时对影响吸附性能的因素进行了分析.     

A REVIEW OF OXYGEN-CONTAINING SURFACE GROUPS AND SURFACE MODIFICATION OF ACTIVATED CARBON

1. INTRODUCTION Activated carbons (ACs) have been widely used as adsorbents in environmental protection, e.g. removing organic or inorganic pollutants from liquid effluents and voltaic organic compounds (VOCs) from polluted air. It has been well known that the adsorptive capacity of ACs is not only determined by its textural properties (e.g. specific surface area, pore size distribution, pore volume), but also related to its surface chemistry. Many studies have demonstrated that the ad…     

A REVIEW OF OXYGEN-CONTAINING SURFACE GROUPS AND SURFACE MODIFICATION OF ACTIVATED CARBON

This review focused on the recent reports related to the function, characterization and modification of axygen-containing surface groups of activated carbon (AC). The Oxygen-containing surface groups were briefly described, and the most frequently used techniques for characterization of the oxygen-containing surface groups on .ACs were also briefly stated .4 detailed discussion of the effects of the oxygen-containing snrface groups on the adsorptive capacity of .4C was given. The recent progresses in modification of the oxygen-containing surface groups of AC were also reviewed     

EFFECT OF HYPERCROSSLINKED RESINS SURFACE CHEMISTRY ON THE ADSORPTION OF PHENOL FROM AQUEOUS SOLUTION

Two hypercrosslinked resins with similar physical characters but different surface chemistry were synthesized and used to remove phenol from aqueous solutions. The FTIR spectra, elemental analysis and the Boehm titration were used to characterize the chemical properties of the resins. The adsorption experiments were carried out using the bottle-point technique, and the effects of the surface chemistry on the adsorption were discussed. The adsorption data fit well with the Freundlich model, indicating the heterogeneity of the resins surface. It could be seen from the experimental results that the adsorption capacity increased with the increase in the total surface concentration of oxygen-containing groups. The pH dependence and the effects of ionic strength were also discussed. The kinetic adsorption data fit well with the pseudo-second order model, and the results showed that the surface oxygen-containing groups have little effect on the adsorption rate.     

Adsorption of ammonia and water on functionalized edge-rich carbon nanofibers

The preparation, characterization and ammonia and water adsorption properties of edge-rich carbon nanofibers (CNFs) were studied, including platelet CNFs (PCNFs) and cup-stacked CNFs (CSCNFs). Since PCNFs and CSCNFs have many chemically active exposed edges, functionalization by oxidizing the edges was carried out by ozone stream and by nitric acid. Transmission electron microscopy, N₂ adsorption isotherms and temperature-programmed desorption analysis showed that the nitric acid treatment partly destroyed the graphite structure of the PCNFs and created acid functional groups and micropores, whereas the ozone treatment created functional groups without damaging the structure. Ammonia adsorption isotherms clarified that NH₃ adsorption on PCNFs and CSCNFs occurred mainly on oxygen-containing groups, whereas the adsorption on activated carbon fibers (ACFs) occurred on both oxygen-containing groups and the carbon surface without the functional groups, and the CSCNFs showed larger amounts of adsorbed ammonia compared to the PCNFs. Especially at a relatively low pressure range (<0.2 atm), the PCNFs/CSCNFs/ACFs showed the same ammonia adsorption mechanism; that is, the one-to-one interaction between oxygen atoms in the functional groups and hydrogen atoms in ammonia molecules. In addition, the adsorption on the ACFs appeared to occur mainly by interaction with the carbon surface at relatively high pressure (0.3–1.0 atm). Our experimental results and previous findings suggest that NH₃ adsorption on PCNFs is due mainly to NH…O hydrogen bonding between oxygen-containing groups and ammonia rather than to chemical bonding.     

Water vapor adsorption and microporous structure of carbon adsorbents. 18. Effect of surface chemistry of activated carbons on water vapor adsorption

This investigation has been devoted to a study of the chemical composition of the surfaces of activated carbons. A study has been made of the way in which changes in the surface chemistry of a series of carbons, as a result of heat treatment, affects the nature of their adsorption of water vapor. A differentiation has been made between oxygen-containing groups found on the surface of activated carbons before and after their heat treatment. It has been established that the original adsorption centers, which play a determining role in water vapor adsorption by activated carbons, comprise functional groups like strongly acidic free hydrogen ions, carboxylic and phenolic groups, situated on on the pore surface of the activated carbons. The number of these functional groups on the pore surface of the activated carbons has been correlated with the parametera ₀ (the number of original adsorption centers) in the isotherm equation for water vapor adsorption. The relative pressure corresponding to the formation of an adsorption layer on the surface of the activated carbons has been shown to depend on the number of original adsorption centers, the acidic functional groups.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 35–40, January, 1991.     

Influence of oxygen plasma treatment on hydrogen chloride removal of activated carbon fibers

The oxygen plasma treatment of activated carbon fibers (ACFs) was carried out to introduce oxygen-containing groups onto carbon surfaces. Surface properties of the ACFs were determined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). N2/77 K adsorption isotherms were investigated by BET and D-R plot methods to characterize specific surface area, pore volume, and pore size distribution. The efficiency of hydrochloride removal was confirmed by two kinds of methods; one is detecting tubes (range: 1-40 ppm), and the other is a gas chromatography technique. As experimental results, the hydrochloride removal efficiency of the ACFs was increased with the number of plasma treatment times up to around 300%, resulting from newly formed oxygen-containing functional groups (especially phenolic and carboxylic) on carbon surfaces, in the decreased specific surface areas or pore volumes. These results indicate that the plasma treatment leads to the increase of hydrochloride removal due to the improvement of surface functional groups containing oxygen on the carbon surfaces.     

Adsorption of Cd(II) ion and its complex compounds from solution on the surface of charcoal treated with an oxidation-negative ionizing method

The adsorption characteristics of Cd(II) from electrolytic solution by activated charcoal have been investigated. It was found that the amount of adsorption of Cd(II) depends mainly on the pH value of the solution, the number of added inorganic ions, and oxygen-containing groups on the surface. The activated charcoal was treated with the oxidation-negative ionizing (OA) method to produce more oxygen-containing groups on the surface. The adsorption amount of Cd(II) on the treated activated charcoal increased remarkably. It was also found that the more powerful the acidity of the surface and the larger the adsorption amount of Cd(II), so the charged groups on the surface of activated charcoal are considered as the main adsorption-activated sites for inorganic ions. The adsorption characteristics of various complexes of Cd(II) on the surface of activated charcoal have also been investigated. Three types of adsorption configuration of the complexes of Cd(II) on the surface of activated charcoal were suggested according to the experimental results.     

空心活性碳纤维SNACF的织构和表面化学结构的研究

本工作借助透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X-射线衍射、X-射线光电子能谱(XPS)、红外光谱和化学滴定等技术,研究了空心活性碳纤维SNAGF的织构和表面化学结构特征。实验结果表明,SNAGF具有多孔性微晶碳结构,其表面存在着碱性官能团和羧基、酚基等酸性官能团及高氧态硫(如磺酸及砜基类等)官能团。     

超声辐射下某些含官能团化合物与二氯卡宾的反应

超声辐射在有机反应中的应用日趋广泛。我们曾报道了超声辐射与相转移催化相结合产生二氯卡宾和二溴卡宾的方法及其与烯烃加成反应的结果。该法比单纯使用相转移催化剂或超声辐射更为可取。本文进一步将它用于二氯卡宾与某些含官能团化合物的反应,考察超声辐射的影响。反应是在固-液两相条件下进行的,即以粉末状氢氧化钠为碱,氯仿过量兼作溶剂。结果表明,超声辐射对各类化合物反应的影响有相当明显的差异。