1070-4272/05/7811-1869+2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 11, 2005, pp. 1869!1871. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 11,
2005, pp. 1900!1902.
Original Russian Text Copyright + 2005 by Levichev, Lobacheva.
OF CHEMISTRY AND TECHNOLOGY
Foam Separation of Nickel and Copper Ions
from Dilute Aqueous Solutions
S. A. Levichev and O. L. Lobacheva
St. Petersburg State University, St. Petersburg, Russia
St. Petersburg State Mining Institute, St. Petersburg, Russia
Received June 3, 2005
Abstract-The minimal expenditure of anionic surfactant, sodium dodecyl sulfate, required for decreasing
concentrations of nickel and copper ions to the maximum permissible concentration was determined experi-
mentally. A possibility of selective recovery of nickel ions by foam separation with sodium dodecyl sulfate
under conditions of complex formation of copper cations with thiosulfate anions was studied.
The maximum permissible concentrations (MPCs)
for nickel and copper cations in water are steadily de-
creased. Fairly recently they were 0.1 mg l
nickel and 1.0 mg l
for copper . The problems
of recovery of salts of these metals from wastewaters
were solved by precipitation flotation , flotation
with a carrier , and foam separation .
Here we present the results of experiments on foam
separation of dilute aqueous solutions containing
copper and nickel salts both separately and in com-
bination, aimed to determine the expenditure of sur-
factant, sodium dodecyl sulfate (SDS), and assess the
possibility of separate recovery of these cations.
One of the mechanisms of foam recovery of ions
from dilute aqueous solutions is ion exchange [10,
11]. Due to adsorption on the bubble walls, a layer of
surface-active ions is formed. In the case of anionic
surfactants these are anions and in the case of cationic
surfactants, cations. These adsorption layers attract
counterions. As a result, diffusion layers of coun-
terions held by Coulomb interaction are formed.
The content of a certain type of counterion is gov-
erned by its valence and concentration in the solution.
The experimental data on the influence of ions on the
surface tension of aqueous solutions of SDS far from
critical micellization concentration (CMC) showed
that, with increasing valence of ion, the surface activ-
ity of cations increases . For ions of the same
valence, the activity is approximately the same. The
increase in the probability of penetration into the dif-
fusion layer due to a high concentration of SDS in
solution suggests that in foam separation it is neces-
sary to decrease the SDS concentration.
To check this assumption, the foam recovery of
copper and nickel cations was carried out as follows.
A glass vessel was charged with 700 ml of a 0.001 M
solution of copper or nickel sulfate or both salts.
The solutions were prepared gravimetrically from
crystal hydrates of analytically pure grade; the concen-
trations of the solutions were checked by EDTA titra-
tion. A disc-shaped bubbler presenting a porous plate
from microporous plastic with a pore size of 33 mm
was placed on the vessel bottom. Air (or nitrogen)
was passed through this plate into the solution; the
flow rate was controlled with a fine adjustment valve.
A 0.05 M SDS solution was fed into the solution
in 5-ml portions, so that the highest concentration of
surfactant in the solution to be treated did not exceed
0.005 M, i.e., it was lower than the CMC. The next
portion of SDS solution was added only after the
solution lost the ability to form stable foam as a result
of transition of the surfactant to the foam. The result-
ing foam was subjected to drainage in a glass vertical
tube 30 mm in diameter, to avoid the loss of the [out-
going] solution. Due to gravity drainage, the dry
transparent foam was withdrawn; in so doing, the
solution weight did not change noticeably. With de-
creasing foam-forming power of the solution, the
height of the drainage column was decreased remov-
ing its separate units. After addition of SDS to the
solution in the equimolar amount relative to the salt
in the solution, the solution was analyzed for content
of SDS and copper and nickel ions.
The SDS concentration was determined by poten-
tiometric titration with an ion-selective electrode for
ionic surfactants. A 1.2 0 10
M solution of a cation-
ic surfactant, cetyltrimethylammonium bromide of