ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 7, pp. 1078!1081. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + L.A. Kupchik, M.P. Kupchik, O.L. Alekseev, E.S. Bogdanov, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 7,
AND ION-EXCHANGE PROCESSES
Effect of Electrosurface Properties of Pectin Substances
on Their Sorption Capacity for Water and Heavy Metals
L. A. Kupchik, M. P. Kupchik, O. L. Alekseev, and E. S. Bogdanov
Institute of Sorption and Endoecological Problems, National Academy of Science of Ukraine, Kiev, Ukraine
National University of Alimentary Technologies, Kiev, Ukraine
Ovcharenko Institute of Biocolloid Chemistry, National Academy of Science of Ukraine, Kiev, Ukraine
Received July 11, 2006; in final form, March 2007
Abstract-Three industrial pectins, viz., citrus, apple, and beet pectins were examined for the chemical com-
position, sorption, and electroosmotic transfer. The gelation concentrations, charge, and binding of the pectins
to water and heavy metals were determined.
Pectins are natural components of plant tissues.
They are commercially produced from various kinds
of wastes from the food industry such as pomace,
citrus peel, beet pulp, and sunflower heads .
The application of pectins as therapeutic, prophyl-
actic, and detoxicant agents is based on their ability to
form hydrogels and insoluble complexes with heavy
metals . These properties of pectin depend on
such factors as the source, preparation route, and
physicochemical characteristics of pectin itself. How-
ever, in the literature we found no systematic data on
the relationship between the physicochemical and per-
formance (hydrophilic, sorption, and electrosurface)
characteristics of industrial pectins, which makes it
difficult to optimize the dosage and therapeutic ap-
proach for these promising natural detoxicants in
prophylactic and medical practice.
In this study we examined correlations between
the chemical, sorption, and electrosurface properties
of various industrial pectins.
We used tree kinds of pectins: PEKTOWIN citrus
pectin (type NEC-A2), PEKTOWIN apple pectin
(type NEJ-A2), and lab-made beet pectin. The charac-
teristics of these pectins obtained by the standard
analytical methods  are summarized in Table 1.
Particularly, the uronic fraction, total carboxy group
concentration, and free and methoxylated carboxy
group concentrations were determined titrimetrically.
The electrosurface characteristics of pectins (maxi-
mal electroosmotic transfer, z potential, and charge of
pectin molecules) were determined according to the
procedures described in . The gelling and sorption
properties (sol/gel point, bound water, and sorption
capacity for water and heavy metals) were charac-
terized using the methods described in .
In all the experiments we observed the transport of
the fluid across the pectin gel toward the cathode,
suggesting a positive charge of the counterions, and,
correspondingly, a negative charge on the pectin
macromolecules. The experimental dependence of the
electroosmotic transfer rate (ETR) on the pectin con-
centration in a gel membrane represents a curve with
a maximum (Fig. 1, curves 133), the initial section of
which characterizes the increase in ETR with decreas-
ing concentration of the dispersed phase. However,
with further dilution, the disperse system passes into
the free-disperse state. In this case, ETR abruptly de-
creases ((Fig. 1, curves 133, the left branch of the
curves). Therefore, the maximum point corresponds to
the transition from the bound-disperse to the free-dis-
perse state (sol/gel transition). This dependence can be
described by Eq. (1):
kk(1 + b)
P = ÄÄÄÄ 3 ÄÄÄÄÄÄÄ, (1)
where P is ETR (cm
, pectin concentration
(wt %); a, specific charge of the pectin particles
); b, specific concentration of pectin-bound
water (g g
); d, density of the dispersion medium
); and k, coefficient reflecting the ratio bet-
ween the speeds of the fluid and counterions (it is
close to unity in our case).