Physicochemical studies on cross-linked thorium(IV)–alginate complex especially the electrical conductivity and chemical equilibrium related to the coordination geometry

Abstract

The electrical conductivity of cross-linked thorium(IV)–alginate complex in the form of circular disc has been investigated as a function of temperature. The Arrhenius plot of logσ vs. 1/T showed a simple parabolic shape at the early stages, followed by a sharply increase in o values with raising the temperature at the final stages. This behaviour was interpreted by the formation of free-radicals at the initial stages, followed by the degradation of the complex at elevated temperatures to give rise to thorium oxide product. The heterogeneous chemical equilibrium for exchange of Th4+ counter ions in the complex by H+ ions has been investigated by titrimetric and complexometric techniques. The thermodynamic equilibrium constant was found to be 26±0.25 dm9mol−3 at 25°C. The X-ray diffraction pattern indicated that thorium(IV)–alginate complex is amorphous in nature. Infrared absorption spectra indicated that Th4+ is chelated to alginate macromolecular chains and displayed υs OCO− and υas OCO− in the ranges of 1419 and 1635cm−1, respectively. A geometrical structure for chelation of thorium(IV) to the functional groups of alginate macromolecule is suggested and discussed in terms of complex stability.