Description of electrolyte fluid dynamics in the electrode compartments by mathematical models can be a powerful tool in the development of redox flow batteries (RFBs) and other electrochemical reactors. In order to determine their predictive capability, turbulent Reynolds-averaged Navier-Stokes (RANS) and free flow plus porous media (Brinkman) models were applied to compute local fluid velocities taking place in a rectangular channel electrochemical flow cell used as the positive half-cell of a cerium-based RFB for laboratory studies. Two different platinized titanium electrodes were considered, a plate plus a turbulence promoter and an expanded metal mesh. Calculated pressure drop was validated against experimental data obtained with typical cerium electrolytes. It was found that the pressure drop values were better described by the RANS approach, whereas the validity of Brinkman equations was strongly dependent on porosity and permeability values of the porous media.

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Electrochemical technologies for the regeneration of spent pickling baths are feasible since they allow simultaneous metal deposition and acid production in the same process unit. In this work, the effect of Fe2+ concentrations on the electrochemical iron deposition from model spent pickling baths is analyzed by voltammetry switching potentials, Tafel plots and spectrum-electrochemistry studies. The analysis showed that the electrodeposition rate and potential decreased as Fe2+ concentration increased. Moreover, at higher Fe2+ concentrations, a decrease on the hydrogen evolution reaction was observed. Moreover, chemical Fe dissolution is present at all concentrations studied, due to the high corrosion rate of iron at low pH of the model bath. Thermodynamic diagrams and electrochemical tests coupled to UV-Vis analysis demonstrated the presence of iron sulfate complexes suggesting that iron deposit is conducted by an inner sphere layer mechanism.