1070-4272/05/7810-1586 C 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 10, 2005, pp. 1586!1590. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 10, 2005,
Original Russian Text Copyright + 2005 by Grebennikov, Udal’tsova, Ustinov.
AND ION-EXCHANGE PROCESSES
Porous Structure of Activated Carbon Fibers
S. F. Grebennikov, N. N. Udal’tsova, and E. A. Ustinov
St. Petersburg State University of Technology and Design, St. Petersburg, Russia
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received February 14, 2005; in final form, July 2005
Abstract-The dependence of the microporous structure of activated carbon fibers on the carbonization
temperature of hydrate-cellulose fibers was studied by BET, TVFMP, and Horvath and Kawazoe techniques
and methods of the nonlocal density functional theory. The surface energy distribution function was obtained,
together with the micropore size distribution curves. It was shown that the effective micropore sizes calculated
by the TVFMP method are close to the maximum of the distribution function found in terms of the theory
of the density functional.
Activated carbon fibers (ACF) differ from the con-
ventional granulated adsorbents in that they make it
possible to create adsorbents in the form of nonwoven
structures, cardboard, fabrics, and other physical en-
tities. The small geometric dimensions of elementary
fibers lead to a substantial increase in the rate of
internal mass transfer. Both the last parameter and
the intensity of mass transfer in the course of ad-
sorption depend on the size of micropores [1, 2]. At
the same time, an objective analysis of the micropore
volume distribution by pore size (MVDPS) is re-
quired in various areas of chemical technology, be-
cause this function determines the applicability fields
and choice of an optimal adsorbent. Polymer pre-
cursors allow a sufficiently wide variation of the
MVDPS. This study is concerned with one of ways
to obtain ACF with various micropore volumes and
sizes, which makes it possible to control the MVDPS
in the existing industrial technology by somewhat
modifying the carbonization mode of the starting pre-
As objects of study served samples of activated
carbon fibers. A technical viscose thread was used
as a precursor. Samples ACF-450, ACF-600, ACF-
800, and ACF-1000 were obtained at different ther-
mal treatment (carbonization) temperatures of 450,
600, 800, and 1000oC, respectively. The carboniza-
tion was performed in an industrial installation in ni-
trogen at the temperatures specified above for 36 min.
Further, thermally treated carbon fibers were steam-
activated at 800oC in an industrial furnace for 6 min.
The resulting ACF had a mostly microporous structure
with small-volume mesopores.
Isotherms of nitrogen adsorption were measured
on a CAMO ERBA STRUMENTAZIONE MICRO-
STRUCTURE 85/02/04 instrument and SORTOMAT-
IC-1900 installation. This was done at a temperature
of 3195.8oC at relative nitrogen pressures p/p
the range from 1 0 10
to 0.85 (Fig. 1).
The adsorption isotherm reflects the porous struc-
ture of adsorbents and makes it possible to calculate
Fig. 1. Isotherms of nitrogen adsorption a (T = 3195oC)
on activated carbon fibers. ( p/p
) Relative pressure.
(1) ACF-450, (2) ACF-600, (3) ACF-800, and (4) ACF-
1000; the same for Fig. 234.