Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 10, pp. 1781−1784.
Pleiades Publishing, Ltd., 2010.
Original Russian Text
T.E. Nikiforova, V.A. Kozlov, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 10, pp. 1642−1645.
OF SYSTEMS AND PROCESSES
Speciﬁ c Features of Sorption of Heavy Metal Ions
by a Cellulose-containing Sorbent
from Aqueous Media
T. E. Nikiforova and V. A. Kozlov
Ivanovo State University of Chemical Engineering, Ivanovo, Russia
Received November 9, 2009
Abstract—Sorption of Cd
, and Zb
ions by a polysaccharide biosorbent was studied. The
effect of the pH of the medium on the process of distribution of metal cations in a heterophase system constituted
by an aqueous solution of a metal sulfate and a cellulose-containing sorbent was determined.
A topical task is to determine the sorption, ion-
exchange, and complexation properties of various
natural materials and ﬁ nd fundamental aspects of
sorption processes involving these substances in order
to expand the assortment of sorption materials used
for puriﬁ cation of aqueous solutions of varied origin,
including food systems, and enterosorbens, food and
biologically active additives.
Promising sorbents for extraction of heavy metal
ions from aqueous media are various phytogenous
substances, produced from renewable raw materials,
such as wood, ﬂ ax, cotton, and formed as wastes in
the agricultural sector and in pulp-and-paper, wood-
processing, and food industries, which all are readily
available and inexpensive [1–3]. Recently, interest has
been expressed in analysis of the sorption properties of
water-insoluble biopolymeric sorbents of polysaccharide
nature (cellulose, chitin, etc.), also named “food ﬁ bers, ”
which exhibit a high binding capacity toward a number
of heavy metals and are contained on products of plant
origin (cereals, legumes, vegetables, fruits, berries,
algae, and fungi) .
Despite difﬁ culties in studies of the relevant sorption
mechanisms, sorbents based on cellulose-containing
materials of plant origin are of indubitable practical and
scientiﬁ c interest and can be regarded as sufﬁ ciently
effective absorbing agents in molecular and ion-
exchange sorption processes.
It is known that the sorption capacity of a cellulose-
based sorbent strongly depends on the acidity of the
aqueous phase, because cellulose-containing polymers
are weakly acid ion exchangers (pK
≈ 9.2). Lowering the concentration of
hydrogen ions in an equilibrium solution leads to an
increase in the degree of dissociation of acid groups of
a polymer, its swelling, and, consequently, to a larger
active surface area of the polymer . Changing the
acidity of a solution will affect the process of metal ion
binding by functional groups of the sorbent, because the
energy of the coordination bond L → H
binding energy L → M (L and M are, correspondingly,
the ligand and metal).
There is no common opinion about the possible
mechanism by which metal ions are sorbed by
cellulose-containing materials: among those reported
in the literature are ion-exchange processes on –COOH
groups, complexation via interaction with –OH groups,
and complexation involving all oxygen atoms of the
elementary unit of cellulose [7–9].
The goal of our study was to examine speciﬁ c features
of sorption of Cu(II), Fe(II), Zn(II), Ni(II), and Cd(II)
ions in a system constituted by an aqueous solution of
metal sulfates and a cellulose sorbent in relation to the
acidity of the medium.