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- PublicationAccès libreOn the determination of surface areas in activated carbons(2005)
;Centeno, Teresa A.The paper examines the validity of two approaches frequently used to determine surface areas in activated carbons, namely the BET method and the use of immersion calorimetry. The study is based on 21 well characterized carbons, whose external and microporous surface areas, Se and Smi, have been determined by a variety of independent techniques. It appears clearly that SBET and the real surface area Smi + Se are in agreement only for carbons with average pore widths Lo around 0.8–1.1 nm. Beyond, SBET increases rapidly and SBET− Se is practically the monolayer equivalent of the micropore volume Wo. This confirms that a characterization of surface properties based on SBET is, a priori, not reliable. The study of the enthalpy of immersion of the carbons into benzene at 293 K, based on Dubinin’s theory, shows that ΔiH consists of three contributions, namely from the interactions with the micropore walls (−0.136 J m−2), the external surface (−0.114 J m−2), and from the volume W*o of liquid found between the surface layers in the micropores (−141 J cm−3). It appears that for carbons where Lo> 1 nm, the real surface area cannot be determined in a reliable way from the enthalpy of immersion and a specific heat of wetting alone.
- PublicationAccès libreCharacterization of industrial activated carbons by adsorption and immersion techniques and by STM(1995)
; ;Centeno, Teresa A. ;Donnet, Jean-Baptiste ;Pusset, NadiaPapirer, EugéneThe results obtained from a variety of techniques (vapour adsorption, selective adsorption of caffeine and immersion calorimetry) used to characterize activated carbons of industrial origin are compared. It is shown that gate effects due to constrictions, and often overlooked, can be revealed by simple experiments with larger molecular probles. Immersion calorimetry appears to be a simple and efficient technique, as illustrated by an activation series. Complementary information is also provided by scanning tunnelling microscopy (STM).