Texture Changes After Oxidative Modification
TEXTURE CHANGES AFTER OXIDATIVE MODIFICATION
OF ACTIVE CARBON GRANULES
B. Buczek, A. Świątkowski
Cracow University of Economics, Faculty of Commodity Science,
31-510 Cracow, Poland
Military Technical Academy, 00-908 Warsaw, Poland
During the oxidative modification of active carbon, the oxidising agent penetrates carbon granules as results of diffusion accompanied by chemical reactions. The process can lead to differentiation of textural and chemical properties inside active carbon depending on the distance from the centre of granule [1,2].
Texture and adsorptive properties of commercial active carbon (Norit 3ex), before and after oxidation using concentrated HNO3, were investigated. Initial active carbon and the oxidised one were separately subjected to abrasion in a spouted bed, thus obtaining core samples with different degrees of external layers removed [3]. For characterisation of porous structure of the carbons, the adsorption and desorption isotherms of benzene were determined. On the basis of benzene adsorption data, the values of Dubinin-Radushkevich equation parameters, total micropore volume (W0) and characteristics energy (E0), as well as the areas mesopores (Sme) and the geometrical surface area (Sg) were calculated [4,5].
Both the active carbon and oxidised one shoved radial differentiation in micro-, meso-, and macropores structure. A changes of the properties throughout the granules is experimental proof that the nitric acid oxidation process occurred in the conditions characterised by the resistance to heat and mass transfer.
References
1. Buczek B., Świątkowski A., COPS-V, 5th International Symposium on the Characterisation of Porous Solids, Heidelberg, Germany, May 30-June 2, 1999, Book of Abstracts P. 322.
2. Buczek B., Biniak S., Świątkowski A., Fuel, 78, 1443 (1999)
3. Buczek B., Langmuir, 9, 2509 (1993)
4. Dubinin M. M., Polyakov N. S. and Kataeva L.T., Carbon, 29, 481 (1991)
5. Bansel R. C., Donnet J. B., and Stoecli , Active Carbon, Marcel Dekker, New York (1991).
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