Physicochemical Studies on some Cross-linked Trivalent Metal-alginate Complexes especially the Electrical Conductivity and Chemical Equilibrium related to the Coordination Geometry

Abstract

The electrical conductivity of cross-linked lanthanum(III)- and cerium(III)-alginate complexes in the form of circular discs has been studied as a function of temperature. The Arrhenius plots of log σ versus 1/ T showed a sharp increase in the electrical conductivity values at elevated temperatures, whereas no changes in σ values were observed at lower temperatures (< 450 K). This behavior was explained by the degradation of the complexes at higher temperatures to give rise to metal oxide products at the final stages. The heterogeneous chemical equilibrium for exchange of La ³⁺ and Ce³⁺ metal ions by H⁺ ions has been investigated complexometrically and titrimetrically. The X-ray diffraction pattern indicated that these complexes are amorphous in nature. Infrared absorption spectra indicated the presence of chelated La³⁺ and Ce³⁺ metal ions with alginate macromolecular chains. A geometrical structure for chelation of lanthanum(III) and cerium(III) to the carboxylate and hydroxyl functional groups of the alginate macromolecule is suggested and discussed in terms of complex stability.