ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 5, pp. 815!819. + Pleiades Publishing, Ltd., 2008.
Original Russian Text + I.M. Lipatova, N.A. Kornilova, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 5, pp. 778!782.
PROCESSES AND EQUIPMENT
OF CHEMICAL INDUSTRY
Effect of Hydroacoustic Treatment on the Rate of Hydrolytic
Degradation of Chitosan in Acetic Acid Solutions
I. M. Lipatova and N. A. Kornilova
Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russia
Received November 15, 2007
Abstract-Effect of a hydroacoustic treatment in a rotary-pulsatory apparatus on the rate of hydrolytic
degradation of chitosan in acetic acid solutions was studied. The influence exerted on the rate of activated
hydrolysis of chitosan by its molecular weight and the process temperature was considered.
The permanent expansion of the possible applica-
tion fields of chitosan makes topical a search for
new methods for production of its chemical deriva-
tives and finely dispersed formulations based on this
polymer. One of new methods of this kind consists
in that the polymer is subjected to intensive mech-
anical treatments in the presence of chemical re-
agents or other modifying ingredients. The capabili-
ties of the solid-phase mechanochemical modifica-
tion of chitosan in devices creating high shear
stresses in strongly compressed solid substances are
being rather intensively studied [1, 2]. The liquid-
phase mechanochemical modification of dissolved
chitosans has not been studied. The liquid-phase
mechanochemical modification of polysaccharides
can be performed via hydroacoustic treatment in
rotary-pulsatory apparatus (RPA) [3, 4]. In ap-
paratus of this kind, the most important factors of
the activating effect on a substance dissolved or
dispersed in a liquid are ultrasonic vibrations and
the resulting cavitation, as well as strong uniaxial
stresses to which the liquid is subjected in the
narrow (0.130.5 mm) gaps between elements of the
rotor and stator [5, 6].
In this study, the effect of the hydroacoustic treat-
ment on the rate of chemical transformations in dis-
solved chitosan was analyzed for the example of the
hydrolytic degradation. It is known that chitosan,
a polyglucosamine of linear structure, dissolves only
in acid media, and, therefore, the acid-catalyzed
hydrolysis of glycoside bonds is the most character-
istic process occurring even in storage of solutions
at room temperature .
In this study we examined the effect of hydro-
acoustic treatment in a rotary-pulsatory apparatus
on the rate of the hydrolytic degradation of chitosan
in acetic acid solutions.
The study was performed with chitosan samples
of domestic manufacture (Bioprogress, Shchelkovo,
Moscow oblast) with molecular weights M =5010
(Kh-500), 3.6 010
(Kh-360), 1.2 010
(Kh-87) whose degrees of deacetylation
(DD) were 0.68, 0.73, 0.78, and 0.82, respectively.
Weighed portions of chitosans were dissolved in
aqueous solutions of 2% acetic acid under agitation
in the course of 435h.
Chitosan solutions were treated in a laboratory
rotary-pulsatory apparatus in the recycle mode.
The thermostated working chamber of the apparatus
is formed by a rotor and a stator whose cylindrical
rings have rectangular channels. In rotor rotation,
there occurs fast alternation of the coincidence and
noncoincidence of the rotor and stator channels,
which gives rise to mechanical vibrations in the
liquid in a wide frequency range, including ultra-
sonic vibrations. The average gap between the rotat-
ing and immobile elements of the working chamber
is 0.5 mm. The rotor rotation rate was 5000 rpm, to
which corresponds a shear rate gradient of 17.4 0
. The treatment duration was varied in the
range 4360 s.
The relative level of the cavitation appearing in
mechanically treated chitosan solutions of various
concentrations was evaluated by the degree of dis-