Diffusion of Phosphate Ion in Xanthan Gum Solutions

Abstract

The diaphragm cell method was used in order to determine the diffusion coefficient of phosphate ion in xanthan gum solutions. The polymer concentration ranged from 0.125 to 2.5 kgm−3 and phosphate ion concentration from 12.5 to 50 mM. Potassium chloride solutions (0.01–5 M) were used in order to study the effect of ionic strength over the diffusion coefficients. All measurements were carried out at 29oC. An important decrease in the diffusional coefficients of phosphate was observed as the polymer concentration increased. Diffusion coefficients were influenced by the ion concentration. Phosphate diffusion coefficients in xanthan solution were a function of the phosphate concentration as well as of the ionic strength (modified by addition of KCl). The Ware model was employed successfully in order to describe the diffusion coefficients as a function of the polymer and salt concentrations.