Journal of Nuclear and Radiochemical Sciences, Vol. 6, No. 3, pp. 221-222, 2005

Sorption of Rhenium on Carbon Fibrous Materials Modified with Chitosan
L. A. Zemskova,a A. V. Voit,a Yu. M. Nikolenko,a V. I. Sergienko,a I. D. Troshkina,*, bA. V. Plevaka,b S. B. Maiboroda,b and A. M. Chekmarevb
aInstitute of Chemistry, Far Eastern Branch of Russian Academy of Sciences, 159, pr. 100- letiya Vladivostoka,690022, Vladivostok, Russia
bD.Mendeleyev University of Chemical Technology, 9, Miusskaya Sq., 125047, Moscow, RussiaReceived: July 31, 2005; In Final Form: September 30, 2005
Sorption behavior of rhenium with respect to new sorption materials was the object of this study in order to define
the possibility of its extraction and concentration from dilute solutions. The sorption materials were prepared bymodifying of high-area carbon cloth with a natural biopolymer – chitosan. The three types of sorption materials
with different degree of amino groups protonation were obtained. Modified materials have higher sorption capacity as compared to initial carbon cloth. Sorption behavior of the materials was found to be conditioned by thenumber of the protonated amino groups. We propose that electrostatic interaction of perrhenate ion ReO4 − withthe protonated amino groups –NH3+ takes place.

Nitrogen containing anionites and complexing ionites aswell as amino containing impregnates are used for sorption ofrhenium, one of the least distributed rare metals. Chitosan, anatural organic polymer containing amino groups can adsorb
ReO4 − and sorption depends on the ionic strength and pH of its
solutions. Specifically, chitosan has primary amino groups
with pK a values close to 6.3. At pH below pK a most of theamino groups are protonated making chitosan a water-soluble
cationic polyelectrolyte. At pH above the pKa chitosan’s aminogroups are deprotonated, and this polymer becomes insoluble1.
These properties of chitosan were used for obtaining of new
sorption materials. It is known that for adsorption of some pollutants (such as organic compounds, metals) from water somehigh-area carbon cloth samples which have the advantage of
having large specific area are used.2, 3 It was also reported4 that
adsorbate could be almost quantitatively desorbed by anodic or
cathodic polarization of C-cloth configured as a porous electrode.
The C-cloth used as initial material for preparing of the sorbents was received from Svetlogorsk PC “Khimvolokno” andcoded as Busofit-T having specific area ~700 –800 m2 /g. It was
modified with chitosan by means of electrochemical process
and adsorption on C-cloth. Thus, the three types of the sorption materials were obtained by the following ways: by cathodicand anodic polarization (in potentiostatic regime) and at opencircuit condition in electrolyte solutions. The amount of precipitated chitosan depends on the treatment method at the sameconcentration. To determine the types of nitrogen containing
groups we used the X-ray photoelectron spectra. X-ray photoelectron N 1s spectra of some samples are presented in Figure
1. Deconvolution of these spectra gives two peaks with a difference in energy of 2.6 eV corresponding to amino groups –NH 2 and protonated amino groups –NH3 +. It was found thatthe chitosan film precipitated at the negative electrode hadmuch less amount of protonated amino groups.
Comparison of the sorption properties of the three series ofsorption materials as regards to rhenium was carried out.
Rhenium sorption from neutral solutions with phase ratio
1:1000 was studied. Figure 2 compares kinetic characteristicsof the sorption materials obtained. All the samples modified*Corresponding author. E-mail: tid@rctu.ru. FAX: +7-095-4907523.

400.0

N(E)
10000

8000

6000

4000

2000a)

Eb, eV
0397

398

399

N(E)

400

401

402403

404

399.7

4000

3000

2000

1000b)

0397

402.3
Eb, eV398

399

400

401

402403404

Figure 1. X-Ray photoelectron N 1s spectra after smoothing andbackground subtraction of carbon-fibers modified with chitosan bycathodic (a) and anodic (b) polarization.

with chitosan under various conditions have higher sorption
capacity as compared to the initial C-cloth. Thus, sorbent
samples prepared by anodic polarization have better kineticfeatures (curve c). This difference helps us to understand therole of amino groups in rhenium sorption. We suppose thatsorption behavior of materials is conditioned by the number ofprotonated groups.

© 2005 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 12/28/2005

222 J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005

Zemskovac)d)

1.0 ΦD (%)100b)
800.8a)0.6600.440a)b)200.20.0t, min020406080

100120−Figure 2. The kinetics of ReO4 sorption on original C-cloth (a) andC-cloth modified with chitosan by cathodic (b) and anodic (c) polarization and at open-circuit potential (d). Here Φ is the degree of thesorption against the equilibrium sorption.
0.5a, mmole/g0.40.3a)b)

0.20.1C, mmole/L
0.0
0.0

0.1

0.2

0.3

0.4

0.5

0.6

−

Figure 3. The isotherm of ReO4 sorption on C-cloth modified withchitosan by anodic polarization and its approximation by Langmur(a) and Freundlich (b) isotherms. Here a is the sorption and C is theequilibrium concentration.

Figure 3 shows the adsorption isotherm of rhenium on thesorbent sample prepared by anodic polarization. The experimental data were fitted using both Langmuir and Freundlichisotherms. The best correlation between experimental data andfit-line as obtained for Langmuir isotherm with the following
parameters – the constant value 13.6 ± 1.5 L/mmole, the maximum capacity – 0.46 ± 0.01 mmole/g. We propose that inadsorption process the protonated amino groups can interact
with the negatively charged perrhenate anion ReO 4 − via electrostatic interaction as in Reference 5. Rhenium desorption
from the sorbent in result of change of its charge may confirm
this proposal. In order to desorb previously adsorbed rheniumt, min0050100150200250−Figure 4. The kinetics of ReO4 desorption at 0 mV (a) and at –100mV (b). Here D is the degree of desorption.

the modified sorbent was negatively polarized with the rate 0.1
mV/sec up to potentials 0 and 100 mV (Ag/AgCl reference electrode) and then was exposed to these potentials. The time ofthe electrode charging since stationary potential up to desorption one was about 1 hour (Figure 4). Exposure to desorption
potentials lets to desorb up to 80% of rhenium. Some decreaseof amount of rhenium desorbed may be due to pH increase at
the electrode layer in the end of the desorption process.
Electrodesorption has some advantages as compared to usual
desorption: it does not require complex reagents, large volumesof solutions or additional equipment. Desorption of ReO4 − ionsby means of polarization is of significance for application, i.e.
for accumulation of ReO4 − ions from dilute solutions with thesubsequent charge desorption into a small volume. Behavior ofReO 4 − ions is similar to that other oxy-ions, such as Mo(VI)and V(V), in the process of their extraction from industrial sewages by means of adsorption and electrosorption at high-areacarbon cloth.
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