Electrochemical hydrodynamics in magnetic fields with laser interferometry: Influence of paramagnetic ions

Abstract

The electrochemical reduction of Zn²⁺ was studied galvanostatically at current densities ranging from 0.10 to 7.0 mA cm⁻² by using the system Zn/ZnSO₄/Zn, and operating it at its natural pH, under the influence of imposed non-variant magnetic field strengths ranging from 0.09 to 0.50 T in the V-position, C/A-position and A/C-position. The convective contours were visibly defined in the V- and A/C positions. The extent of convection in the C/A-position was negligible in the presence of the applied magnetic field. The presence of a paramagnetic ion (Mn²⁺ or Cr³⁺) in the medium produced noticeable deviations in the concentration gradients. The mass transport coefficient for Zn²⁺ was evaluated in the presence of the applied magnetic field. The fluid flow velocities in the reduction of Zn²⁺ under the imposed magnetic field were estimated at 1–7 cm s⁻¹. The diffusion layer relaxation was followed by the fringe shift, after the electrolysis had terminated. The relaxation mechanism appears to be a slow rotational and translational movement of the paramagnetic fluid in the C/A-position. The exact mode of interaction between the magnetohydrodynamic effect, studied previously, and the paramagnetic effect studied in this work is not yet obvious. It is proposed that the mechanism by which energy dispersion is limited and momentum conserved is by suppression of microturbulence in the non-variant magnetic field.