This communication deals with the simulations of turbulent flow, mass transport and tertiary current distribution on the cathode of a rotating cylinder electrode reactor (RCE) in continuous mode of operation. The electrolyte inlet was located at the bottom and the electrolyte exit at the top. Silver electrodeposition (1300 ppm Ag(I) in 23000 ppm CN⁻ at pH 13) was employed as a model system. A 316-type stainless steel cylinder with a 3.8 cm diameter and a length of 11 cm was used as a cathode, while six Ti-IrO₂ plates were used as anodes. Electrolyzes were performed at holding potential of −1.2 V SCE, which guaranteed mass transport control. The volumetric inflow rate tested was 0.1 L min⁻¹ giving a mean flow rate of 0.037 cm s⁻¹ (performed at the inter-electrode gap). The rotational speeds at the RCE surface were 100, 200, 300, 400, and 600 rpm (peripheral velocity of 10.5, 20.9, 31.4, 41.9, and 62.8 cm s⁻¹; Re of 7600, 15100, 22700, 30200, and 45400, respectively). It is worth mentioning that the peripheral velocities predominate in two magnitude orders over the inflow electrolyte rate. Therefore, the mass transport is determined by the electrode rotation speed.¹ Simulations were obtained solving the RANS equations with the standard k−ε turbulence model. For mass transport simulations, the averaged diffusion-convection equation was solved. For the simulations of tertiary current distribution, wall functions were adapted. The current distribution along the RCE interface in the z-coordinate developed one edge effect near to the electrolyte inlet, afterwards, homogeneous current distribution was attained. The edge effect is formed by the abruptly silver concentration depletion at the electrolyte inlet. Excellent agreement between mass transport correlation and current distribution simulations with experimental data were obtained.

References

1. M. Rosales, and J.L. Nava, J. Electrochem. Soc., 164 (11), E3345 (2017).