OF SYSTEMS AND PROCESSES
Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 2, pp. 202−217.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © S.N. Yashkin, A.A. Svetlov, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 2, pp. 213−228.
Adsorption Properties of Surface of Carbon Materials
at Extremely Low Coverages
S. N. Yashkin and A. A. Svetlov
Samara State Technical University, Samara, Russia
Received January 18, 2011
Abstract—Adsorption properties of blacks and their graphitized analogues were examined by the inverse gas
chromatography at extremely low surface coverage.
Most of the known techniques of static and dynamic
adsorption are not suitable for examination of a state of
surface of adsorbents distinguished by their structure and
chemical nature in extremely low surface coverages .
This hampers research of the most active surface sites
whose amount is generally low but their contribution
to adsorption properties as a whole is signiﬁ cant. The
inverse gas chromatography (IGC) in the case of inﬁ nite
dilution makes possible a direct examination of adsorp-
tion properties and parameters of the most active surface
sites in a region of adsorption isotherm close to the zero
surface coverage . The reported surface sites can vary
greatly in the chemical and phase composition that is
simultaneously reﬂ ected through values of their potential
adsorption energy. These differences determine a degree of
energy heterogeneity of the adsorbent surface . Nowa-
days, IGC takes leading position among the contemporary
physicochemical methods for investigation of solid surface
, solutions of low- and high-molecular compounds [5,
6], catalysts  etc. owing to possibility of the rigorous
thermodynamic substantiation of the found quantities,
varying of external conditions (temperature, pressure), and
virtually unbounded range of reference adsorbates
Various types of carbon black applied in a manufacture
as ﬁ llers of polymeric materials and coloring pigments
 are of great interest for the study of the adsorption
activity and energy heterogeneity of the surface. There-
with the properties of the most active sites of the carbon
material surface and associated with them of different
allotropic modiﬁ cations (including nanoscale formations)
are practically not studied. A set of unique properties of
these formations are directly dependent on the structure
and energy state of the surface.
The study is devoted to the examination of adsorption
chromatographic properties of the carbon black surface
with the help of an analysis of thermodynamic parameters
of adsorption (TPA) of molecule probes at the extremely
low surface coverages.
Main physicochemical parameters of the carbon
blacks under study are listed in Table 1.
Experimental values of TPA of the molecule probes
capable of intermolecular interactions of various types
[n-pentane (dispersion), benzene (induction), acetonitrile
(orientation)] were determined under conditions of gas
adsorption chromatography by a Tsvet chromatograph
in the isothermal mode with a ﬂ ame ionization detector.
Samples of the carbon blacks were subjected to prelimi-
nary extraction with different solvents in a Soxhlet ap-
paratus [toluene 36 h, the mixture of CH
O (1 :
1) 36 h]. Figure 1 shows a typical chromatogram of the
separation of the extract in toluene for an N660 carbon
Adsorbents for the study were kindly provided by employees of the
German Institute for Rubber Technology (Hannover, Germany) and
the ﬁ rm Degussa (Germany).