1070-4272/05/7812-2019 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 12, 2005, pp. 2019!2021. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 12, 2005,
Original Russian Text Copyright + 2005 by Alekseev, Arapov, Polovtsev, Charykov, Izotova, Potalitsin.
Methods for Purification of Carbon Nanotubes
Obtained from Fullerene Production Deposits
N. I. Alekseev, O. V. Arapov, S. V. Polovtsev, N. A. Charykov,
S. G. Izotova, and M. G. Potalitsin
Innovations of Leningrad Institutes and Enterprises Closed Joint-Stock Company, St. Petersburg, Russia
Ioffe Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, Russia
St. Petersburg State University, St. Petersburg, Russia
State Institute of Applied Chemistry, St. Petersburg, Russia
Received June 2, 2005
Abstract-Methods of preparation and purification of nanocarbon materials (nanotubes, nanobarrels, nano-
bulbs) from deposits formed in fullerene production were developed.
Since the beginning of extensive studies of carbon
nanotubes (CNTs) and other nanostructures in 1991
[1, 2], the separation of CNTs from concomitant prod-
ucts (amorphous carbon, graphite, and sometimes cat-
alyst metal particles) has become an increasingly top-
ical problem, strongly affecting the CNT cost.
At present, the purest CNTs (< 90%) are prepared
by their CVD growth in the presence of catalysts on
special supports [3, 4]. In this case, the amount of
amorphous carbon is relatively small, graphite is vir-
tually absent, and catalyst metal particles can be elim-
inated by comparatively brief treatment with an acid.
Various pathways of purification of CNTs prepared
by CVD are described in  and depend on CNT
type (single- or multiwalled). However, only small
CNT amounts can be prepared by CVD, and, therefore,
this method is not widely used today. Nevertheless,
a CVD method for preparation of single-walled nano-
tubes containing no impurities was described in .
The HIPCO method , which is essentially sim-
ilar to CVD and involves preliminary synthesis of
catalyst particles in the gas phase, gives CNTs with
a high content of excess catalyst, which requires a
complex purification procedure .
Very complex treatment is required for CNT-con-
taining raw material obtained by electric arc synthesis,
which is the most productive now [11, 12]. Accord-
ing to , the purification procedure in the arc
synthesis of single-walled CNT with a catalyst must
be multistep. However, this method (arc + catalyst) is
also inefficient and is claimed only when just single-
walled CNTs are required.
When multiwalled CNTs with varied size and ori-
entation are applicable (e.g., as catalysts, hydrogen
accumulators, etc.), a common noncatalytic arc meth-
od of CNT preparation is used . In this case, a de-
posit formed on the cathode during recrystallization
of the carbon evaporated from the anode surface is
the source of CNTs. An apparatus for fullerene gen-
eration, produces during continuous work for one day,
up to 1 kg of soot and 2003300 g of a deposit con-
taining up to 10 g of CNTs .
These amounts of the deposit require that strongly
different treatment procedures should be used to sep-
arate amorphous carbon and graphite constituents. For
example, it was shown in  that selective oxidation
in air at 700oC proceeds slowly. The deposit ground
to 503100-nm particles loses no more than 50% of
the initial weight upon a 12-h treatment. Other gaseous
oxidants were also ineffective. Rotation of the work-
ing volume of a tubular furnace substantially accel-
erates the treatment of the ground deposit . How-
ever, this technology is suitable only for a small vol-
ume of the material treated. Treatment with acids 
is only efficient at continuous addition of fresh por-
tions of the acid and small amounts of the deposit
(a few grams per 100 ml of working volume). Treat-
ment of larger amounts is possible in a countercurrent