Diffusion of Fe3+ Ions in Agar Gel Medium Containing Zinc Sulfate: Obstruction effect and Activation Energy

Abstract

The paper presents a study on the diffusion behaviour of ferric ions within an agar gel medium containing zinc sulfate electrolyte. Investigations for various aspects, including the obstruction effect introduced by the agar gel, the validation of Wang's diffusion model, and the suitability of applying transition state theory to the diffusion of Fe3+ ions in an agar gel medium with zinc sulfate were made. This investigation involved optimising the gel concentration, electrolyte concentration, and system temperature. The diffusion coefficients are determined by the zone diffusion technique. The results reveal that the activation energy (E) decreases as the electrolyte concentration increases, aligning with Wang's model. This decrease is attributed to the disruption of the water structure induced by ions and agar molecules. Additionally, for a fixed electrolyte concentration, the activation energy decreases with the cubic root of the weight percent of agar (W1/3), while the diffusion coefficient (Do) decreases with the square of the reciprocal of the weight percent of agar (W-2/3). This behaviour is consistent with the principles of the transition state theory of diffusion.