Download COMPLEXING ABILITY OF REE IMMOBILIZED IN A POLYMER

COMPLEXING ABILITY OF REE IMMOBILIZED IN A POLYMER MATRIX OF
POLYVINYL ALCOHOL
* Sh.К. Amerkhanova, **Azwan MatLazim, *** L.N. Siromakha, * А.S. Uali,
* G. Prnazarova, * N.Kurbanaliev
*E.A. Buketov Karaganda State University, Karaganda, Kazakhstan;
** National University of Malaysia, Kuala Lumpur, Malaysia;
*** Pavlodar State Pedagogical Institute, Pavlodar, Kazakhstan
e-mail: [email protected]
The effect of temperature and ionic strength on the immobilization process of rare earth elements
in the polyvinyl alcohol are investigated by the pH-metric method. The stability constants of complexes
are determined. It is shown that the interaction of metal ions with polymeric ligands occurs mainly due to
electrostatic effects.
The interest in the study of the interaction of rare earth elements’ salts (REE) with high-molecular
compounds (HMC) are increasing in recent years. These reactions play an important role in the selective
transport of metal ions through the membrane, solubilization of inorganic salts in organic solvents,
biological enzyme systems, etc. The researches aimed at clarifying the application of interaction products
of HMC with the rare earth elements as solid polymer electrolytes in solid-state batteries and
accumulators, fuel cells, chemical registration systems, sensors and displays are intensively developed
too. Ionic conductors based on polymeric materials have several advantages over existing and currently
used by solid electrolytes, such as silver iodide.
The action nonmetalocene organometallic derivatives of rare earth metals in the catalysis of
unsaturated substrates’ transformations are considered in /1/. Hydride complex of yttrium catalyzes the
polymerization of ethylene at 65°C and a pressure 4 atm in deyterobenzole /2,3/.
The complexation of REE with 2.2'- dipyridyl is studied by authors V.P. Smagin and others /4/.
From practical point of view, choice of rare earth elements as complexing ions due to their original
luminescent properties, which appear in the liquid and solid solutions. So investigation of complexing
ability of rare earth elements with polyvinyl alcohol in aqueous solutions is actually.
pH-metric measurements were performed at pH METER-pH 410 /5/ and the stability constants of
complexes of REE are determined by this method (Fig. 1). Thermodynamic parameters were calculated
base on the temperature dependence of stability constants of complexes.
lgβ
12
Y3+
11
10
Ce3+
9
ZrO2+
8
Rb +
7
Cs+
T, K
6
295
300
305
310
315
320
Fig. The stability constants of rare earth ions’ complexes with PVA under the influence of temperature, I
=0
It is established that the in stability constants’ decrease with increasing temperature is characteristic
for cerium (III) ions, zirconium ion, rubidium ion, and it is associated with destruction of hydrogen bonds
between water molecules and polymer mesh, as well as increasing the hydration’ degree of complex REE
with PVA /6/.
On the other hand, all the cations are hard Lewis acids according to C.B. Yatsimirskii classification
of donors and acceptors, so they predominantly form ionic bonds with ligands. In this case, they are
strongly polarized, as they have a noble gas electron configuration, and hence their formed bonds (M n+ O) are more polar and exposed to a greater extent influence of temperature.
Also it should be noted that the values of stability constants decrease at 318 K with in cation
charge, i.e. symbatically to ionic potential, which for these cations is Mn+ Ce3+>ZrO2+> Rb+. Thus,
according to /7/ the tendency to complexes’ formation is reduced in this line. However, the line changed
may happen at low temperatures due to the influence of the solvent. It is seen on the example of trivalent
yttrium, as well which at 298 K, more susceptible to hydration, and hence forms outer-sphere complexes
/6/.
At the same time the stability constants increase with increase the rise of temperature for the Y3+
and Cs+ ions; coordination number as CN ion and electron structure play an important role in the
formation of the complex. The trivalent yttrium ions have unfilled d-orbitals and also refer to the dcations, so their formed bond have not only ionic but also donor-acceptor character /8/.
The cesium ion is the most active among the alkali metals and the most electropositive element, but
it is less polarized than the rubidium ion, and it forms sufficiently labile bonds with the oxygen atom of
PVA’s hydroxo-group and water molecules.
Thus, the immobilization of rare earth cations into the polymer matrix requires high temperatures
to reduce the influence of solvent on the complexation process. These results can be used to develop
highly efficient catalytic systems based on rare-earth elements, which are used in fine organic synthesis.
1.
2.
References
Trifonov А.А. Uspekhi Khimii. 2007. -Vol. 76, № 11.- С. 1122-1144.
Duchateau R., Van Wee C. T., Meetsma A., Teuben J.H. J. Am. Chem. Soc., 1993.- 115:
4931.
3.
Duchateau R., Van Wee C.T., Teuben J.H. Organometallics, 1996.- 15: 2291.
4.
Smagin V.I., Yudina Е.V.//Russian Journal of inorganic chemistry.- 2005.- Vol. 50, № 2.С. 213-218.
5.
Amerkhanova Sh. K., Shlyapov R.M., Uali A. S. Solution thermodynamics of rare-earth
metal ions – physicochemical study// IUMRS-ICA 2008 Symposium «A. A. Rare-Earth Related Material
Processing and Functions” IOP Publishing IOP Conf. Series: Materials Scienceand Engineering, 2009.1.- P. 1-6.
6.
Bakeev M.I. Hydration theory and properties of electrolyte solutions.-Karagandy.Publ.house of KarSU.- 2007.- 221 p.
7.
Voskresenskaya О.О., Skorik N.А. Thermodynamic and kinetic aspects of formation and
redox-decomposition of cerium (IV) complexes with hydroxy organic ligands. Monograph.-Tomsk:
Publ.house NTL, 2011.- 220 p.
8.
Gromada J., le Pichon L., Mortreux A., Leising F., Crapentier J.-F.. J. Organomet.
Chem., 2003.- 44: 683.