Use of Water-Insoluble Surfactants for the Removal
of Small Amounts of Transition Metal
Nitrates from Water
A. Zh. Ambartsumyan and Sh. A. Markaryan
Yerevan State University, Yerevan, Armenia
Received July 21, 2009
Abstract—The removal of small amounts of cobalt and nickel nitrates from water with the use of water-
insoluble surfactant, dioctadecyldimethylammonium bromide, was studied.
ISSN 1070-4272, Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 9, pp. 1668–1670. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.Zh. Ambartsumyan, Sh.A. Markaryan, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 9, pp. 1572–1574.
At present the removal of water from industrial
wastes is the major ecological problem. It also causes
the fact that, despite of the presence of numerous
refining procedures, searching for new technologies of
the extraction of metal ions from industrial waters is
still in progress.
Classical extraction methods, such as extraction in
a liquid–liquid system, are ineffective, especially when
it is necessary to remove small amounts of ions from
water, as in this case a certain part of an organic phase
is dissolved in water, and also a considerable amount
of water is consumed .
Recently a great attention is given to micellar
extraction, which is based on the formation and
following removal of surfactant-ion complexes from a
solution by means of ultrafiltration. This method is
interesting due to the fact that, depending on the
surfactant nature, a selective extraction of metal ions
from solutions becomes possible [2–4].
The new method of extraction of ions is presented
in this work. It is based on the property of water-
insoluble surfactants to form ordered monolayers on a
water surface, in which polar groups of surfactants are
oriented aside an aqueous phase and hydrophobic parts
of molecules, aside a gas phase. It has been shown that
the slightest amounts of cations of transition metals in
the form of the complex anions [CoBr
or mixed aquabromonitrate complexes can be removed
from a solution with the help of a monolayer of diocta-
decyldimethylammonium bromide (DODA) formed on
a water surface.
The major problem is the accurate calculation of
such concentration and volume of a DODA (Aldrich-
Sigma, 99.9%) solution (М
= 630 M) that would form
a saturated monolayer on a liquid surface after
chloroform evaporation. The surface area of a solution
in a funnel is 112 cm
. The calculation was based on
the plot of surface pressure against an area occupied by
one DODA molecule on the water surface. It was
shown earlier  that when the saturated monolayer is
formed each DODA molecule occupies an area of
about 60 Е
on a water surface. In view of these data
we have calculated the number of DODA molecules
necessary to form a monolayer with the area of
, in which the molecules are closely spaced.
The calculation has shown that 20 μl of an 1 M DODA
solution in chloroform form the required monolayer.
To extract Co
cations from aqueous
solutions of the Co(NО
O and Ni(NО
salts (REAKHIM, chemically-pure grade), 100 ml of a
M solution of a salt under study were poured in a
separatory funnel previously washed out in an H
mixture [70 ml of H
(98%) + 30 ml of H
(35%)]. Then an 1 M DODA chloroform solution
(20 μl) was placed on the liquid surface where it
spread instantaneously. After chloroform evaporation a
formed DODA monolayer remained on the liquid