Activated carbon fibres

Moehida, I., Kuroda, K., Kawano, S., Matsumura, Y. and Yoshikawa, M., Kinetic study of the continuous removal of SO, on polyacrylonitrilc-bascd activated carbon fibres. 1. Catalytic activity of PAN ACF heat treated at 800 °C,Fuel, 1997, 76(6), 533 536. 

AJcafiiz-Monge, J., de la Casa-Lillo, M. A., Cazorla-Amoros, D. and Linarcs-Solano, A., Methane storage in activated carbon fibres. Carbon, 1997, 35(2), 291 297. 

Choi J, Hirai M, Shoda M. 1991. Catalytic oxidation of hydrogen sulphide by air over an activated carbon fibre. Applied Catalysis A General 79 241-248. 

L. Agiii, A. Guzman, P. Yanez-Sedeno and J.M. Pingarron, Voltammetric determination of chloramphenicol in milk at electrochemically activated carbon fibre microelectrodes, Anal. Chim. Acta, 461 (2002) 65-73. 

Guillot A, Stoeckli F, and Bauguil Y. The microporosity of activated carbon fibre KF1500 assessed by combined C02 adsorption and calorimetry techniques and by immersion calorimetry. Adsorpt. Sci. Technol., 2000 18(1) 1-14. 

The [Au(en)2]3+ cation has also been used to deposit gold onto activated carbon fibres by ion exchange of protons in acidic (phenolic) surface groups 101 reduction in hydrogen gave 2-5 nm particles (see also Section 4.5.4). 

Modifying activated carbon fibres (ACF) by ferric oxide improved the gold dispersion and their activity at room temperature, but they deactivated quickly.111... 

Agui, L., Vega-Montenegro, D., Yanez-Sedeno, P. and Pingarron, J. M. (2005), Rapid voltam-metric determination of nitroaromatic explosives at electrochemically activated carbon-fibre electrodes. Anal. Bioanal. Chem., 382(2) 381-387. 

Activated charcoal was originally regarded as a relatively inexpensive adsorbent with an assortment of pores of ill-defined size and shape. However, in recent years considerable progress has been made in the development of tailor-made porous carbons such as molecular sieves, activated carbon fibres and carbon composites (Marsh et al., 1997). Superactive carbons are now made on a commercial scale with BET areas of around 3000 m2g-1. Activated carbons can be manufactured as fine particles or granules or in the form of a cloth, felt or consolidated membrane. The properties of some of these special types of activated carbon are discussed in Chapter 12. 

A study of the hydrophilic sites on the surface of activated carbon fibres has been made recently by Kaneko et al. (1995) with the aid of X-ray photoelectron spectroscopy (XPS). In this work cellulose (CEL)- and polyacrylonitrile (PAN)-based activated carbon fibres were used and samples were either chemically treated with H202 or heated in H2 at 1000°C. As expected, surface oxidation by the H202 treatment increased the initial uptake of water, while the H2 reduction caused a marked decrease in the amount of water adsorbed at low p/p°. Measurement of the peak areas of the XPS spectra provided a means of determining the fractional surface coverage by the hydrophilic sites. In this way a linear relationship was found between the low-pressure adsorption of water vapour and the number of hydrophilic sites (mainly —COOH). 

It was not long before the first activated carbon fibres (ACFs) were developed. In the work of Economy and Lin (1971, 1976) highly porous carbon fibres were prepared from Kynol, a fibrous phenolic precursor. Carbonization was carried out in nitrogen at 800°C and activation occurred in steam at 750-1000°C. The products appeared to be predominantly microporous and were found to be effective for the removal of low levels of certain pollutants (e.g. phenol and pesticides) from air or aqueous solutions. 

In recent years, extensive studies have been undertaken by Kaneko and his coworkers of the properties of activated carbon fibres (ACFs) produced from cellulose, polyacrylonitrile (PAN) and pitch. X-ray diffraction and electron microscopy revealed that the PAN-based and pitch-based fibres had a more homogeneous pore structure than that of the cellulose-based material, although the latter had the largest surface area and pore volume (Kakei et al., 1990). 

Similarly, there is a great potential in the use of water vapour for the analysis of the porous texture, because it has considerable potential due to both the easy experimental conditions (at room temperature the whole range of relative pressures can be covered) and the characteristics of the molecule itself (polar molecule and small kinetic diameter-0.28 nm). This vapour is widely used in the characterisation of inorganic porous solids, such as zeolites, silicas, and clays. However, its interaction with carbon materials (microporous carbons coals, activated carbon fibres, carbon molecular sieves and porous carbons activated carbons), is more complex than the interaction of non-polar molecules [8]. 

In previous studies, we have investigated water adsorption in activated carbon fibres (ACFs), which are mainly microporous solids with a well-defined pore structure, and some activated carbons (AC) containing micro, meso and macroporosity [9,10]. On all these materials, we were able to show that water adsoiption in micropores depends on the micropore size, taking place gradually according to the pore size. It was concluded that adsorbed water in microporosity is in a solid, ice-like phase, with a density around 0.92 g.cm The present paper presents the results corresponding to the extension of this research to CMS, studying both the mechanism of water adsorption in carbonaceous solids and the suitability of water adsorption to characterise CMS. 

Waste air cleaning using activated carbon fibre cloths regenerable by direct electric heating... 

Accurate information on the isotherm trends of various VOC groups (in relation to the individual boiling points of low, medium and high boilers) was essential in order to describe the entire process and to elaborate a suitable design for the plant. The isotherms of various VOCs were measured on a commercial microporous ACC using the equilibrium apparatus previously described. The specific surface of this activated carbon fibre cloth was 1000 mVg, pore diameter was between 1 and 2 nm and the specific pore volume for solvents was 0.45 cmVg. 

Isotherms of various microporous solids (activated carbons, zeolites, ACF s), involving different adsorbates (N2, CO2, Ar), have been measured Norit R1 Extra (N2, CO2), Norit RBI (N2), Norit C Granular (N2), Chemviron BPL-HA (N2), Chemviron ASC-TEDA (N2), an experimental activated carbon AC 147 (N2), a pitch-based activated carbon fibre (P3200-C02/900°C) manufactured at DSTL-Porton Down (N2), zeolite 13X14H (N2) and zeolite 13X12L (Ar). The last one was copied from the reference isotherms provided with the Mi-cromeritics ASAP 2010 poresizer that was used to measure the different isotherms. 

Recently, both the fundamentals of CO2 adsorption and its applicability are gaining interest [9-13]. From studies conducted with activated carbons and activated carbon fibres [9,10], CO2 adsorption at 273K and at sub-atmospheric pressures has been proposed as an appropriate alternative to assess the ultramicroporosity [10,11]. Despite that N2 and CO2 have similar critical dimensions, since CO2 adsorption is carried out at a temperature higher than its boiling point the gas molecules can enter the narrowest porosity of the solid [4,8-13]. 

Fig. 4.14. SANS of oriented activated carbon fibres, (a) Schematic representation of a sample of carbon fibres oriented with their axes parallel to the incident neutron beam (b) corresponding anisotropic scattering along the two axes of the 2D detector, (i) SANS along the vertical axis, (ii) SANS along the horizontal axis of the detector [101].

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