MASS-TRANSFER AT THE GAS EVOLVING INNER ELECTRODE OF A CONCENTRIC CYLINDRICAL REACTOR

Mass transfer coefficients for an oxygen evolving vertical PbO2 coated cylinder electrode were measured for the anodic oxidation of acidified ferrous sulphate above the limiting current. Variables studied included the ferrous sulphate concentration, the anode height, the oxygen discharge rate and the anode surface roughness. The mass transfer coefficient was found to increase with increasing O2 discharge rate, V, and electrode height, h, according to the proportionality expression K proportional-to V0.34h0.2. Surface roughness with a peak to valley height up to 2.6 mm was found to increase the rate of mass transfer by a modest amount which ranged from 33.3 to 50.8% depending on the degree of roughness and oxygen discharge rate. The present data, as well as previous data at vertical oxygen evolving electrodes where bubble coalescence is negligible, were correlated by the equation J = 7.63 (Re.Fr)-0.12, where J is the mass transfer J factor (St.Sc0.66).