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.     

纳米碳纤维的表面性质和微结构对氧还原催化活性的影响

采用超声处理的方法分别对管式纳米碳纤维(t-CNF)和鱼骨式纳米碳纤维(f-CNF)进行了表面化学处理. XPS结果表明, 在混酸(浓硫酸+浓硝酸)和氨水中进行超声化学处理可以在CNF表面分别引入含氧官能团和含氮官能团. 电化学测试结果表明, 2种不同微结构CNF的氧还原催化活性都遵循相同的趋势, 即CNF-P相似文献   

Influence of anodic treatment on heavy metal ion removal by activated carbon fibers

In this work, the effect of electrochemical oxidation treatment on activated carbon fibers (ACFs) was studied in the context of Cr(VI), Cu(II), and Ni(II) adsorption behavior. Ten weight percent phosphoric acid (A-ACFs) and ammonia (B-ACFs) were used for acidic and basic electrolytes, respectively. Surface properties of ACFs were determined by X-ray photoelectron spectroscopy (XPS). The specific surface area and the pore structure were evaluated from nitrogen adsorption data at 77 K. As a result, the electrochemical oxidation treatment led to an increase in the amount of oxygen-containing functional groups. Also, the adsorption capacity of the electrochemically oxidized ACFs was improved in the order B-ACFs > A-ACFs > untreated-ACFs, in spite of a decrease in specific surface area which resulted from pore blocking by functional groups and pore destruction by acidic electrolyte. It was clearly found that the heavy metal ions were largely influenced by the functional groups on the ACF surfaces.     

Ammonia removal of activated carbon fibers produced by oxyfluorination

In this study, activated carbon fibers (ACFs) were produced by an oxyfluorination treatment to enhance the capacity of ammonia gas removal. The introduction of polar groups, such as CF, CO, and COOH, on the ACFs was confirmed by a XPS analysis, and N2/77 K adsorption isotherm characteristics including specific surface area and total and micropore volumes were studied by the BET and t-plot methods. The ammonia-removal efficiency was confirmed by a gas-detecting tube technique. As a result, the specific surface area and micropore volume of ACFs were slightly destroyed as the surface treatment time was increased. However, the oxyfluorinated ACFs led to an increase of fluorine and oxygen-containing polar functional groups in ACF surfaces, resulting in an increase in the ammonia-removal efficiency of the ACFs produced.     

Effect of acidic treatment on metal adsorptions of pitch-based activated carbon fibers

In this work, the pitch-based activated carbon fibers (ACFs) were prepared by nitric acid to investigate the multi-metal adsorption in interfacial and textural points of view. N2/77 K adsorption isotherm characteristics, including the specific surface area and micropore volume, were studied by BET specific surface area and t-plot methods, respectively. As a result, the specific surface area of the almost neutral ACFs in nature significantly decreased with nitric acid treatment, probably due to the widening of micropores. However the total acidity, including the carboxyl groups, on carbon surfaces was extremely induced during the acidic surface treatment. From the adsorptions of Cu2+ and Ni2+, it was revealed that the adsorption capacity of metal ions was mainly influenced by the weakly acidic functional groups such as lactones on the carbon surfaces at pH < pI (isoelectric point), and by the strongly acidic functional groups such as carboxyl groups at pH > pI.     

气相生长碳纤维的表面改性及表征

用浓硝酸(65%~68%)对气相生长碳纤维(VGCF)进行了不同时间的表面化学改性。X射线衍射(XRD)分析表明：改性使得VGCF的石墨晶型结构改变，其改变的程度随改性时间的延长而加深；BET比表面积(S_BET)测试表明：改性后的VGCF的S_BET有一定的变化，经120 min长时间的改性处理后，S_BET明显降低；傅立叶变换红外光谱(FTIR)测定得出：改性后VGCF表面上生长了不同类型的含氧基团，其总含量随改性时间的增大而增加；程序升温还原(TPR)得出：改性后VGCF表面上生成有2类以上的热稳定性不同的含氧基团，计算求得含氧基团的氧总含量为2 mmol·g^-1以上；NH₃吸附微量量热测定得出：表面酸性基团的强度和含量随改性时间增加而增大；透射电子显微镜(TEM)结果表明：改性没有明显破坏VGCF的外观结构；吸油值(AOV)实验给出：改性后VGCF的AOV显著降低而亲水性增强；双液法接触角测试给出：改性后VGCF的表面能(SE)明显增大；偶联剂与VGCF作用的FTIR研究表明：改性后VGCF表面含氧基团和偶联剂发生反应，增强了偶联剂在VGCF表面上的结合强度。     

Effect of ozone treatment on ammonia removal of activated carbons

In this work, activated carbons (ACs) were modified by ozone treatment to enhance the efficiency of removal of ammonia gas over the ACs. Surface properties of the ACs were confirmed by X-ray photoelectron spectroscopy (XPS) analysis and N2 adsorption isotherms at 77 K were investigated by BET and D-A methods to characterize the specific surface area, total pore volume, and micropore volume. The ammonia removal efficiency was confirmed by the gas-detecting tube technique. The results showed that the specific surface area and micropore volume of ACs were slightly destroyed as the ozone treatment time increased. However, the ozone treatment led to an increase in ammonia removal efficiency of ACs, mainly due to an increase of acid functional groups, such as carbonyl and ether groups, on carbon surfaces. It was revealed that the improvement of ammonia removal efficiency of ACs was greatly affected by the interfacial acid-base interactions between modified ACs and basic ammonia adsorbate.     

Adsorbents based on carbon microfibers and carbon nanofibers for the removal of phenol and lead from water

This paper describes the production, characteristics, and efficacy of carbon microfibers and carbon nanofibers for the removal of phenol and Pb(2+) from water by adsorption. The first adsorbent produced in the current investigation contained the ammonia (NH(3)) functionalized micron-sized activated carbon fibers (ACF). Alternatively, the second adsorbent consisted of a multiscale web of ACF/CNF, which was prepared by growing carbon nanofibers (CNFs) on activated ACFs via catalytic chemical vapor deposition (CVD) and sonication, which was conducted to remove catalytic particles from the CNF tips and open the pores of the CNFs. The two adsorbents prepared in the present study, ACF and ACF/CNF, were characterized by several analytical techniques, including SEM-EDX and FT-IR. Moreover, the chemical composition, BET surface area, and pore-size distribution of the materials were determined. The hierarchal web of carbon microfibers and nanofibers displayed a greater adsorption capacity for Pb(2+) than ACF. Interestingly, the adsorption capacity of ammonia (NH(3)) functionalized ACFs for phenol was somewhat larger than that of the multiscale ACF/CNF web. Difference in the adsorption capacity of the adsorbents was attributed to differences in the size of the solutes and their reactivity towards ACF and ACF/CNF. The results indicated that ACF-based materials were efficient adsorbents for the removal of inorganic and organic solutes from wastewater.     

介孔炭表面性质对吸附去除低浓度氨性能的影响

室内环境中低浓度氨污染普遍存在,影响人的身体健康,而消除这些低浓度的氨相对困难。本文报道了一种适用于低浓度氨吸附去除的介孔炭材料,其性能明显优于经硝酸处理的活性炭材料。该介孔炭采用磷酸铝为硬模板制备,炭表面存在大量含氧官能团,研究显示炭表面羧基和内酯基在吸附氨过程中发挥着重要作用,它们作为酸性中心与氨发生化学作用,可以有效地捕获空气中低浓度的氨污染物。     

Adsorption of Basic Dyes Using Walnut Shell-based Biochar Produced by Hydrothermal Carbonization

Hydrothermal carbon(HC) was prepared from walnut shells, which are abundant in Northeastern China. The prepared HC was used as a precursor to produce nitric acid modified carbon(MC). The hydrothermal carbonization included dehydration and decarboxylation processes wherein the hemicellulose was completely decomposed and the cellulose was partly decomposed, with some oxygen-containing functional groups being produced. The aromati-city, specific surface area and pore content of the HC increased, but its polarity decreased. With 6 mol/L nitric acid and a modification time of 15 min, the specific surface area and pore content decreased, but the proportion of oxygen-containing functional groups on the surface increased significantly, thereby improving the dye adsorption performance. The adsorption of methylene blue and malachite green was best described by the pseudo-second-order kinetic and Langmuir isotherm models. The adsorption capacity of MC was determined to be much larger than that of HC.     

The influence of low-temperature oxidation of active carbons by nitric acid on their physicochemical properties

The influence of oxidation by nitric acid on the character of oxygen-containing functional surface groups and porous structure of active carbons is considered. Adsorption properties of the initial and oxidized carbons are studied using adsorption isotherms of vapor of n-hexane and polar substances (water and methanol).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1132–1137, May, 1996.     

Low Temperature Catalytic Hydrolysis of Carbon Disulfide on Activated Carbon Fibers Modified by Non-thermal Plasma

In order to improve the carbon disulfide (CS₂) catalytic hydrolysis efficiency of activated carbon fibers (ACFs), ACFs surface was modified by non-thermal plasma (NTP). In particular, the effects of modification conditions on the catalyst properties were studied, including the reactor structure, modification atmosphere, modification time, output voltage and discharge gap. The catalytic activity study showed that ACFs with NTP modification enhanced CS₂ catalytic hydrolysis. The optimal reactor structure, modification atmosphere, modification time, output voltage and discharge gap was a coaxial cylinder, an N₂ atmosphere, 5 min, 7 kV and 7.5 mm, respectively. The effect of the NTP modification on the micro-structural properties of the ACFs was characterized using scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and X-ray photoelectron spectroscopy (XPS) methods. The results showed that NTP modification improved the dispersion of functional groups and increased the number of oxygen-containing and nitrogen-containing functional groups, thus the catalytic activity could be enhanced. The present results indicated that NTP modification was an effective way to manipulate ACFs surface properties for the CS₂ catalytic hydrolysis reaction.     

Studies on pore structures and surface functional groups of pitch-based activated carbon fibers

The present study concerns the physical activation and chemical oxidation of pitch-based activated carbon fibers (ACFs) as ways to improve the adsorption properties. The surface oxides of the ACFs studied were determined by Boehm's titration and the pore structures were studied by the BET method with N(2)/77 K adsorption. Also, the adsorption properties of the ACFs were investigated with chromium ion adsorption by different adsorption models. As a result, it was observed that carboxyl groups were largely created after nitric acid treatment on ACFs. The affinity for chromium ions increases with increasing specific surface area, micropore volume, and surface functionalities of ACFs as the activation time increases.     

表面改性炭材料在微生物燃料电池中的应用(英)

研究了在空气阴极微生物燃料电池中修饰方法如硝酸处理和硝酸-氨水酸碱等对XC-72R作为阴极氧还原催化剂催化活性的影响,并且使用傅里叶变换红外光谱(FTIR)、Boehm滴定法和X射线光电子能谱(谱(XPS)等手段对催化剂进行了表征.FTIR测试证明硝酸处理可引入含氧基团氨水处理可引入含氮基团.另外,还测试了含有不同表面官能团的XC-72R对氧还原的活性,并将其作为阴极催化剂用在MFC中,测试了电池性能.实验表明,经酸碱修饰的XC-72R作为空气阴极MFC的催化剂具有很好的应用前景.     

碳纳米纤维的酸处理及其负载Pd-Pt的催化萘加氢活性

采用浓硝酸和浓硫酸混和液(90、120、150 ℃)处理鱼骨类和平行类碳层排布的碳纳米纤维. 运用高分辨电镜、红外光谱和离子交换对碳纳米纤维的表面性质进行了表征，并考察了以两种碳纳米纤维为载体的Pd-Pt催化萘加氢活性. 结果表明，碳纳米纤维的碳层排布不同使混酸处理的鱼骨类表面生成的极性含氧基团的量明显高于平行类表面，以前者为载体得到Pd-Pt催化剂金属颗粒的分散程度明显高于后者，其负载的Pd-Pt催化萘加氢活性也较高.     

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.     

Nanosized anatase titanium dioxide loaded porous carbon nanofiber webs as anode materials for lithium-ion batteries

Nanosized anatase titanium dioxide loaded porous carbon nanofibers (TiO₂/PCNFs) were prepared from electrospun TiO(OAc)₂/PAN/PMMA composite precursor fibers with different amount of PMMA porogen, which were sequentially heat-treated in different environments. Electrochemical measurement results show that these as-prepared TiO₂/PCNFs present higher cyclic reversible capacity than the TiO₂/CNFs counterpart (without PMMA porogen in its precursor fibers). Among the as-prepared TiO₂/PCNFs samples, the representative TiO₂/PCNFs (the mass ratio of PAN to PMMA is 3:1) exhibits the best high-rate performance with a high stable capacity retention about 200 mAhg^{− 1} at a current density as high as 800 mAg^{− 1}. This novel TiO₂/PCNFs composite material opens up a promising application in high-power lithium-ion batteries.     

New theoretical insight on the acid sites distribution,their local structures and acid strength of the SAPO‐11 molecular sieve

ONIOM(DFT:PM3) calculations were carried out to investigate and characterize possible acid sites of SAPO‐11 molecular sieve. Two functionals were employed: B3LYP and ωB97X‐D. This last functional includes dispersion effects that are absent in the former. Benzene, pyridine, and ammonia interaction energies as well as the OH stretching frequencies of the POH, SiOH, and bridged Si(OH)Al groups were used to characterize the acid sites. This work shows that the adsorption of benzene on the surface is as strong as the adsorptions inside main channel of SAPO‐11. Pyridine adsorption on the surface is weaker than the one corresponding to the main channel. NH₃ molecule interacts strongly with all OH groups or acid sites present in SAPO‐11. Moreover, the results reveal that it is possible to adsorb two NH₃ molecules at only one Brønsted site. The adsorption of the second NH₃ molecule is energetically favorable mainly due to the hydrogen bond formation between the NH₃ molecules. In general the interaction energy increases with the type of functional used, according to the trend ωB97X‐D > B3LYP. The results show that ONIOM methodology seems to be suited to investigate the acid sites in SAPO‐11.     

聚丙烯腈活性炭纤维对硫化氢的常温吸附

聚丙烯腈活性炭纤维（PAN-ACF）对硫化氢（H2S）有比其他活性炭材料更强的吸附能力。H2S在PAN-ACF上的吸附是一个兼具物理吸附特征的化学吸附、催化转化过程。其化学吸附位主要位于微孔表面。吸附过程为：H2S分子首先被物理吸附进入微孔空间,而后在微孔表面的化学吸附位上进行包含电子转移的化学吸附、催化氧化,在炭表面产生相对稳定的化学结构。     

Aminated metal-organic framework (NH2-MIL-101(Cr)) incorporated polyvinylidene (PVDF) hybrid membranes: Synthesis and application in efficient removal of Congo red from aqueous solution

The efficient treatment of wastewater containing organic dyes generated in diverse industrial processes has become more crucial owing to increasing environmental concerns. In this paper, we incorporated the aminated functional NH₂-MIL-101(Cr) into the porous polyvinylidene fluoride (PVDF) to fabricate the MOFs/polymer hybrid membranes, which combined the surface activity of MOFs and the membrane's filtration plus the adsorption process, and can be used in the high-efficient removal of congo red (CR) from aqueous solution. Two synthesis strategies were employed, and both of which are useful in fabricating the NH₂-MIL-101(Cr)@PVDF hybrid membranes. The NH₂-MIL-101(Cr) particles are mainly incorporated into the pores of PVDF, and thus enhance the hydrophilicity, water flux as well as porosity of the hybrid membranes. In the adsorption experiments, the influences of various conditions including the solution pH, adsorption time, adsorption isotherms, reusability, and the filtration performances were investigated systematically, and all the hybrid membranes show evidently improved adsorption performances compared to original PVDF films. The adsorption thermal and dynamics analyses indicate that the adsorption process is mainly featured in Langmuir monolayer adsorption and chemical adsorption. The hydrogen bonding at the interface of CR/NH₂-MIL-101(Cr) is responsible for the selective adsorption of CR. The excellent reusability and the dynamic adsorption performances determine the potential applications of MOF-based hybrid membranes in the membrane separation of CR from practical waste water.