Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 5, pp. 629−634.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © V.S. Erasov, A.Z. Galimova, T.S. Solov’eva, M.Yu. Pletnev, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 5,
AND INDUSTRIAL INORGANIC CHEMISTRY
The Structure and Adsorption Properties of Colloidal Silica
Used in Toothpastes
V. S. Erasov
A. Z. Galimova
T. S. Solov’eva
, and M. Yu. Pletnev
Moscow State University of Fine Chemical Technologies, Moscow, Russia
Splat-Kosmetika Limited Lability Company, Moscow, Russia
Received February 13, 2013
Abstract—The dispersity, speciﬁ c surface area, porosity, and pore size distribution are determined for samples
of colloidal silica and calcium o-phosphate, toothpaste constituents. The results obtained show that adsorbents
have the developed mesoporous structure. It was found that the adsorption of sodium lauryl sulfate and a nonionic
surfactant, glyceryl monocaprylate, at the aqueous surfactant solution–colloidal silica interface is small and has
the unusual character. The reasons for a low adsorption of surfactants and their mixtures on the surface of the
studied adsorbents are discussed.
Highly porous colloidal silica is used in industrial
processes and as medical, cosmetics, hygiene, and other
products. Toothpastes belong to highly ﬁ lled disperse
systems containing functional and active components
such as surfactant, abrasive ﬁ llers, thickeners, bactericide
additives, and food ﬂ avorings. Along with phosphates
and chalk, colloidal mesoporous silica having selective
sorption capacity and mild abrasive action on the tooth
enamel is increasingly used. Gel pastes containing this
biologically inactive and multifunctional component are
almost transparent and possess required structural and
mechanical properties .
The adsorption properties of colloidal silica have been
studied in detail [2–6]. At the same time, silica with a
highly developed mesoporous structure is studied to lesser
extent . It is suggested that anionic surfactants weakly
interact with the negatively charged silica particles. Silica
as adsorbent for binary surfactant mixtures from aque-
ous solutions is poorly studied. The above systems are
signiﬁ cant for practice and may exhibit the synergetic and
antagonistic effects, consisting in enhancing or reducing
of foaming, antibacterial, and other properties. Therefore,
their study is of interest.
The goal of the study was to determine the structural
and adsorption properties of some samples of colloidal
silica in comparison with calcium o-phosphate, which are
common abrasive components of gel toothpastes.
We studied the adsorption of surfactant mixtures of
different nature in order to determine the mutual enhance-
ment or reduction of the properties of the adsorbents
chosen. Test objects were anionic surfactant, sodium
lauryl sulfate (SLS) and nonionic surfactant, glyceryl
monocaprylate (GMC). The former is common foaming
and cleaning toothpaste ingridient and the latter, foam
stabilizer, hydrotrope, and preservative synergist.
Precipitated sorbosil colloidal silicas AS33 and AS39
from PQ Corporation were used. The samples differed in
the abrasions [a radioactive dentine abrasion (RDA)]: 180
and 50, respectively. According to the supplier, silica par-
ticles have nearly spherical shape and a developed porous
structure. Silica granules are 4–20 μm aggregates of sec-
ondary particles about 20–50 nm in size, the latter formed
by primary particles about 5 nm in size. The values of
the average particle size and RDA of the studied silica
samples are reported in . In addition to silica samples,
we also used Cafos FT calcium o-phosphate, Ca
from the Budenheim Chemische Fabrik (Germany).