Applications of porous flow through electrodes. II. Hydrogen evolution and metal ion removal at packed metal wool electrodes

Abstract

Packed metal wool electrodes have been used for producing hydrogen electrolytically and for removal of Cu2+ ions from a flowing electrolyte stream. Current-potential relations for the two reactions were measured under various operating conditions. The polarization behaviour of the packed wool electrodes has been characterised and interpreted. The effects of pore electrolyte resistance and bed thickness on the polarization of the hydrogen evolution reaction were evaluated and interpreted in terms of an existing model. The effect of the generated gas bubbles on the pore electrolyte resistance is the underlying reason for the measured excessive ohmic potential drops. It has been shown that wool-packed electrodes perform better than, or at least as well as, particle-packed electrodes (turnings, wirelets, small cylinders). The weight of metal wool needed to achieve these results is only about 10% of the weight of the metal particles. The mass transfer at the packed wool electrode has been analysed.