AND POLYMERIC MATERIALS
Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 8, pp. 1275−1281.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © S.B. Selyanina, L.N. Parfenova, M.V. Trufanova, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 8, pp. 1341−1347.
A Comparative Study of Surfactant Properties of Aromatic
Macromolecular Compounds of Lignin and Humus Nature
S. B. Selyanina, L. N. Parfenova, and M. V. Trufanova
Institute of Environmental Problems of the North, Ural Branch, Russian Academy of Sciences, Arkhangelsk, Russia
Received June 26, 2012
Abstract—Solutions of macromolecular compounds of lignin and humus nature were studied by the methods of
surface tension and foaming. The kinetic parameters of the adsorption layer formation on the liquid–gas phase
boundary were determined. In the capability to decrease the surface tension of water, the compounds of lignin and
humus nature are comparable with classical low-molecular-weight surfactants.
Biopolymers of lignin and humus nature are charac-
terized by amphiphilic properties, polydispersity, and
heterogeneity of structural elements. Analysis of such
objects is complicated by the probability character of
their structure, lack of exhaustively studied reference
samples, and limitations in using commonly accepted
procedures [1, 2].
Many-year studies showed that humic compounds of
peat differ essentially from those extracted from other
natural sources [1, 3]. The main genetic feature of humic
substances of peat is the dependence of their composition
and properties on the chemical composition of plants from
which the peat has been formed, in particular, on their
lignin content, as lignin is the major source of aromatic
fragments of peat humus.
Different researchers have essentially different opin-
ions on the capability of humic substances to decrease the
surface tension of water. Ignoring the fact that long time is
required to attain the adsorption equilibrium in solutions
of macromolecular surfactants, the majority of authors
conclude that the surface activity of these substances is
low (10–15 mN m
) [4–10]. At the same time, separate
papers report higher values of the maximal depression
of the surface tension in aqueous solutions of humic
substances, 25–35 mN m
[11, 12]. Taking into account
similar character of compounds of lignin and humus
nature, their important role in biological processes, and
similar ﬁ elds of their application, in particular, as natural
surfactants, it seems appropriate to make a comparative
study of their surfactant properties.
As investigation objects we used lignosulfonates pre-
pared by bisulﬁ te cooking of wood, kraft lignin, and peat
polymers of humus nature in the salt form. The prepara-
tion and characteristics of kraft lignin and lignosulfonate
samples have been described in detail in [13, 14]. Sodium
humates were recovered by alkali extraction, preceded by
debitumenization with butyl acetate, from moss-type peat
samples (the main peat-producing plant was sphagnum)
taken in the region of the research site (Primorskii raion,
Arkhangelsk oblast). The degree of degradation of peat
was 15–20%, the ash residue was 5.7%, and the content
of polymers of humus nature (counting on humates) was
42.4%. The characteristics of the polymers (molecular
weights, functional group content) are given in Table 1.
The behavior in solutions and at the liquid–gas phase
boundary was characterized by variation of the surface
tension σ of the solutions, measured by Wilhelmy’s
method  allowing monitoring of the kinetics of the
surface adsorption layer formation and ensuring high ac-
curacy and reproducibility of the results, and also from the