Thermoconvective instability during electrodialysis

A laser interferometry method is proposed for studying the instability of concentration fields during electrodialysis. It is shown that exceeding the limiting diffusion current density first gives rise to alternating oscillations and then to oscillations at the membrane whose ionogenic groups exhibit the lowest catalytic activity towards the water dissociation reaction. Thereafter, the auto-oscillation process extends over the whole solution volume in the compartments, and dissipative chaos is observed with a further increase in the current density. This instability is presumably a consequence of unevenly distributed heat sources, namely, the Joule heat and the heat of dissociation and recombination of water molecules.