Concentration Profiles and Reaction Fronts in A + B -> C Type Processes: Effect of Background Ions

TL;DR

This paper investigates how background ions influence diffusion, reaction fronts, and pattern formation in ion reactions, revealing that background ions significantly alter reaction front properties and pattern development.

Contribution

It introduces a reaction-diffusion model incorporating background ions and analyzes their impact on reaction front dynamics and pattern formation.

Findings

Background ions affect the effective diffusion constant of reaction fronts.

Unequal ion mobility leads to nontrivial concentration profiles.

Background ions influence Liesegang pattern formation.

Abstract

Diffusion and reaction of initially separated ions A- and B+ in the presence of counter ions A'+ and B'- is studied. The dynamics is described in terms of reaction-diffusion equations obeying local electroneutrality, and the time-evolution of ion-concentrations is determined. We find that, in the absence of reactions, unequal mobility of ions generate nontrivial features in the macroscopically observable concentration profiles. Switching on the reaction (A-) + (B+) -> C leads to the formation of a localized, diffusive reaction front and one finds that the properties of the front (e.g. effective diffusion constant) are affected by the background ions. The consequences of this effect on the formation of Liesegang patterns is discussed.