ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 7, pp. 1140 !1144. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + S.B. Selyanina, N.V. Selivanova, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 7, pp. 1170 !1174.
AND POLYMERIC MATERIALS
Hydrophilic!Oleophilic Properties of Sulfate Lignin
S. B. Selyanina and N. V. Selivanova
Institute of Environmental Problems of the North, Ural Division, Russian Academy of Sciences,
Received October 2, 2006; in final form, December 2006
Abstract-Effects of extractive resinous substances, type of wood, and pH on the hydrophilic!oleophilic
behavior of solid lignin recovered from sulfate delignification liquors were evaluated.
Pulp industry is a primary consumer of wood, the
yield of the final product being as low as about 50%.
The sulfate cooking provides for total utilization of
spent cooking liquors. This process necessarily in-
volves recovery of sulfate soap as micellar aggregates,
followed by production of tall oil by acid treatment.
In this case, kraft lignin transferred into the soap
emulsion with black liquor forms an insoluble solid
product . In the presence of lignin, a stable
heterogeneous system (so-called lignotall emulsion or
lignin phase) is formed. According to the modern
views [4, 5], the lignin phase represents an oil-in-
water emulsion. Lignin tends to concentrate at the
interface, screening the surface of the oil droplets
distributed throughout the bulk of the liquid and thus
preventing their coalescence, i.e., stabilizing the emul-
sion. Therefore, the stability of such systems appears
to be controlled by the characteristics of the stabilizer
In this study, we examined the hydrophilic3oleo-
philic behavior of kraft lignins, as one of their most
important characteristics as emulsion stabilizers.
Generally, the hydrophilic3oleophilic properties
of surfaces are characterized by the ratio of the work
of adsorption of a substance from the hydrocarbon
(oil) and aqueous phases using the Bancroft rule ,
or by the conventional Rebinder relationship  for
saturated hydrocarbons and water.
The classical method for determination of the gas
adsorption on the surface of solid lignin is the gra-
vimetric method with the use of a McBain quartz
spring balance. This method is quite descriptive,
being, however, characterized by complex hardware
implementation and long time of analysis. The vacu-
um-static method is simpler and allows analysis of
several samples in parallel . This method is widely
used for characterization of various sorbents. How-
ever, we found no indications in the literature for its
use in analysis of lignin.
The lignin samples were allowed to stand in an ad-
sorption cell until saturation, i.e., to constant weight
of the sample. The final result was obtained as
an average of three replicate experiments; the data
scatter did not exceed 10% relative to arithmetic mean
(P = 0.95).
The degree of hydrophilicity a was estimated by
= = /
are the limiting adsorptions of water
vapor and hexane, respectively (mol g
The degree of oleophilicity b was estimated as
> =1!=. (2)
When the adsorption cell was not evacuated prior
to the experiment, the degree of oleophilicity es-
timated from the experimental specific adsorptions of
hexane and water was within 0.1330.16, while that
determined with the McBain balance was 0.5330.58
and 0.6530.70 in coniferous and deciduous lignins,
As seen from Fig. 1, preliminary evacuation of
the adsorption cell does not affect the specific adsorp-
tion of water vapor on the lignin surface, being, how-
ever, a crucial factor in adsorption of hexane, which is
probably due to the difference in the vapor pressure.
The specific adsorption of hexane vapor approaches
the equilibrium value at a residual pressure in the ad-