Raman Spectroscopic Study of the Ion Association of Lithium Sulfate Aqueous Solutions

Abstract

A Raman spectroscopic study of Li2SO4aqueous solutions as function of concentration and temperature was performed. The dynamic properties of the sulfate ions were studied by a band profile analysis of their internal modes using Fourier transform methods. This analysis reveals the perturbation of the SO42-vibrations due to ionic interactions. From the v1 (SO4−2) band profile the spectroscopic ionic association constant was calculated in the range from 5 to 80 °C. The large difference found between the values thus obtained for the association constant and the values obtained from macroscopic measurements is interpreted, assuming that Raman spectra reflect only the short-range forces acting on the ions. Using the Bjerrum equation to calculate the contribution for the long-range forces, good agreement is found between the spectroscopic and macroscopic results. © - Verlag der Zeitschrift für Naturforschung