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Adsorption isotherms of carbon dioxide on microporous active carbons have been obtained at 195 K. The adsorption isotherms were interpreted by means of the Dubinin-Astakhov (DA) and Dubinin-Radushkevich-Stoeckli (DRS) equations. The heterogeneity of micropore structure and the energetic heterogeneity of the active carbons were determined from the differential distribution of the micropore volume...
The heat of adsorption of toluene on Maxsorb AW20, a high surface area microporous activated carbon, has been determined by flow microcalorimetry (FMC) at pore fill fractions ranging from 0.5 to 0.95. Consistent determination of the integral molar heat of adsorption requires independent measurement of the equilibrium adsorption isotherm. Molar heats determined from FMC/isotherm data are in qualitative...
Mesoporous carbon xerogels were prepared from the sol-gel polymerization of resorcinol with formaldehyde (RF) followed by carbonization. The effect of the initial pH of the RF solution on the surface area, pore volume, pore size distribution and nanostructure was studied. A brief mechanism of polymerization is discussed. Typically, a lower initial pH yielded carbon xerogels with a higher surface...
Almond and pecan shells were chosen as hard, lignocellulosic precursors for the production of granular activated carbons (GACs) in order to create carbons for the adsorption of both organic compounds and metals. They were activated either chemically, with H 3 PO 4 , or physically, with CO 2 , under a variety of conditions. Following activation, a portion of the GACs were...
The performance of activated carbons in an environment containing two contaminants was evaluated theoretically. A mathematical model developed earlier was used to determine the effect of different parameters on the breakthrough curves of binary mixtures through activated carbon. Due to the difference between the adsorption capacity of carbon for the two components of a binary mixture, one of the...
The adsorption of binary vapour mixtures from air by active carbon beds can be predicted with a good accuracy by adapting a model developed earlier for single vapours. This model is based on a semi-implicit finite difference scheme. Multiple adsorption of vapours is described by the combined theories of Myers-Parusnitz and of Dubinin (MPD), which have already been applied successfully to static...
Isotropic pitch-based carbon fibres are activated by carbon dioxide and by steam at a temperature ranging from 850 to 1000°C. In both cases, a significant increase in micropore volume, as measured by physical adsorption of N 2 and CO 2 , is found. Fibre diameter steadily decreases during gasification by steam. In contrast, an intermediate diameter increase is observed during activation...
Physical and chemical properties of carbons previously used for air purification in sewage plants are investigated. The chosen samples are characterized by pH values (estimated according to ASTM D 3838) between 2 and 10. Their H 2 S breakthrough capacities are less than 0.01 g of H 2 S/cm 3 of carbon. The surface chemistry and porous structure are determined using sorption...
A model based on a new derivation of the equations derived by Amundson and by Bohart and Adams to describe flow in carbon filter beds is presented. A scaling argument is used to explain the discarding of the local time derivative of effluent concentration and it is rigorously shown that the Bohart and Adams model is a special case of the model derived by Amundson. The theoretical results are supported...
Pore size control of a series of activated carbon fibers was attempted by chemical vapor deposition (CVD) of benzene to clarify the influence of the pore distribution on the development of molecular sieving ability. Weight increase by CVD was found to saturate at a certain level respective to the fiber, reflecting their surface areas. However, when saturation was obtained, the molecular sieving...
Activated carbon honeycomb structures based on synthetic precursors are described. These strong, highly durable honeycombs are continuous interpenetrating structures of activated carbon and a ceramic with adjustable broad range of carbon percentage (5-95 wt%). Dynamic adsorption performance of a particular honeycomb structure containing 18 wt% carbon is described with respect to various adsorbates,...
The gas desorption properties of mixed graphite and water glass (K 2 SiO 3 + H 2 O) were investigated by thermal desorption spectroscopy. It was observed that mainly H 2 O and CO 2 were desorbed from the materials after a baking treatment in the atmosphere. The surface morphology became rough or smooth as the graphite content or the water glass increased,...
Monte Carlo computer simulations are reported for the sorption of Ar at 90K in several pores of different shapes. In all cases, the pore walls were modeled as perfectly flat graphitic planes that have been assembled to form pores with rectangular cross-sections characterized by having one dimension fixed at a value that allows four layers of argon in the full pore (with one exception). The second...
The ability of various alkanes to be intercalated into the second-stage cesium graphitide, CsC 24 , was investigated using the two-bulb technique. The structural changes occurring during intercalation were studied by real-time neutron diffraction. At moderate pressure, the intercalation of large molecules such as n-butane, n-pentane and n-hexane simultaneously leads to a mixture of a second-stage...
The present investigation was undertaken to determine the adsorption properties and evaluate the adsorption capacities of several coal- and wood-based chemically activated carbons using the Dubinin–Radushkevich (DR) characteristic adsorption analysis. Limiting micropore volumes (W 0 ), determined from CCl 4 and acetone adsorption isotherms at room temperature, were generally in good...
NH 3 and H 2 S adsorption studies on coal- and wood-based chemically activated carbons were carried out at room temperature using a gravimetric adsorption technique. The adsorption capacity of NH 3 and H 2 S in the very low relative pressure range was independent of the surface area development. Activated carbons with lower surface area generally adsorbed more of these...
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