Charcoal nitrogen adsorption

Qadeer, R. Hanif, J., and Majeed, A., Characterisation of metal-impregnated charcoal Nitrogen adsorption, Adsorpt. Sci. Technol., 12(2), 101-108(1995). 

Fig. 5.13 Adsorption isotherms on graphitized and on ungraphitized charcoal, (a) Adsorption of water vapour (fc) adsorption of nitrogen at — 195°C. The adsorption values are expressed in cm of liquid adsorbate per gram of adsorbent. (Courtesy Kiselev. )...

The area per gram of activated charcoal as determined by nitrogen adsorption is typically in the range 300-1000 m /g. Why is this value different from that determined in this experiment ... 

Figure 2.2 Illustration of pore volume distribution curves for charcoal as obtained from a nitrogen adsorption isotherm (solid curve) and from a mercury porosimeter (broken curve). From data in Adamson [15].

Figure 9.13. Nitrogen adsorption isotherms ar 77 K (a) and corresponding as plots (b) for charcoal cloth JF012 after prc-adsoiption of nonane followed by outgassing at indicated temperature (after Carrott etal., 1989).

Reference data for the adsorption of benzene, dichloromethane and methanol have been used to construct as plots for the adsorption of these vapoius on Carbosieve, Takeda molecular sieve carbons, Maxsorb superactivated carbons and a charcoal cloth. It is shown that the as method can give satisfactory results when applied to organic adsorptives provided that good quality adsorption data at higher pressures is available. It is also shown how analysis of the as plots can lead to useful information about the pore structure of the different types of carbon, and some of the difficulties associated with the use of nitrogen adsorption at 77K for the characterisation of microporous carbons are discussed. 

Denoyel, R., Femandez-Colinas, J., Grillet, Y., and Rouquerol, J. (1993). Assessment of the surface area and microporosity of activated charcoals from immersion calorimetry and nitrogen adsorption data. Langmuir, 9, 515-18. 

Four commercial samples of activated charcoals were used in most of the work, the specific surface areas ranging from 3.5 X 10 to 1.3 X 10 cm.Vg., as measured by nitrogen adsorption. It must, however, be made clear that the data on surface coverage quoted in the paper are based on effective areas determined by the use of the adsorbate used in the experiment. These effective areas were always less than the areas determined by nitrogen ad-... 

Surface Areas of Polymer Charcoals by Adsorption Of Nitrogen and Carbon Dioxide... 

The two sets of activated charcoals studied here, were already characterized by gas adsorption (8) and immersion microcalorimetry into pure liquids (methanol, benzene, cyclohexane, n-hexane and a-pinene) (9). The main results from nitrogen adsorption are summarized in Table I. 

The effects of dyeing on the porosity of samples of charcoal cloth and cotton fabric have been examined from nitrogen adsorption isotherms. So too has the effect on the cotton fabric of mercerisation, a treatment which causes dimensional changes to the constituent fibres. On application from 1% sodium chloride solution, increased contents of dye in the charcoal cloth progressively block the micropores and reduce mesopore area but treatment with sodium chloride solution alone increases microporosity. Mercerlsation of the cotton fabric enhances the mesoporous nature of the surface. The effect on porosity of treatment with a reactive dye is less clear-cut it is tentatively suggested that application of the dye narrows the mesopores. 

Fig. 1. (a) Nitrogen adsorption isotherms and (b) corresponding dt. plots for samples of charcoal cloths. Open points - adsorption Filled points-desorption. A, cloth exposed to 1% sodium chloride solution B, untreated cloth C, cloth containing 10.0% dye. 

For other adsorptives the experimental evidence, though less plentiful than with nitrogen, supports the view that at a given temperature the lower closure point is never situated below a critical relative pressure which is characteristic of the adsorptive. Thus, for benzene at 298 K Dubinin noted a value of 017 on active carbons, and on active charcoals Everett and Whitton found 0-19 other values, at 298 K, are 0-20 on alumina xerogel, 0-20-0-22 on titania xerogel and 017-0-20 on ammonium silicomolybdate. Carbon tetrachloride at 298 K gives indication of a minimum closure point at 0-20-0-25 on a number of solids including... 

Fig. 5.14 Adsorption isotherms of water on carbon in (a) to f) with corresponding isotherms of nitrogen in (a), (c) and (J), and of benzene in (f>). (a) Charcoal (b) active carbon AY8 (c) charcoal A (J) charcoal (e) a coal tar pitch kilned at 1200°C (/) a charcoal (S600H). (Redrawn from the diagrams in the original papers.)...

Massonne, J. et al., Angew. Chem. (Intern. Ed.), 1966, 5, 317 Adsorption of nitrogen trifluoride on to activated granular charcoal at — 100°C caused an explosion, attributed to the heat of adsorption not being dissipated on the porous solid and causing decomposition to nitrogen and carbon tetrafluoride. No reaction occurs at +100°C in a flow system, but incandescence occurs at 150°C. 

J. Dewar Found selective adsorption of oxygen from a mixture with nitrogen, during the uptake of air by charcoal 1904... 

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