Mm. Saleh et al., ELECTROWINNING OF NONNOBLE METALS WITH SIMULTANEOUS HYDROGEN EVOLUTION AT FLOW-THROUGH POROUS-ELECTRODES .2. EXPERIMENTAL, Journal of the Electrochemical Society, 142(12), 1995, pp. 4122-4128
This paper presents an interpretation of the experimental results obta
ined on the electrowinning of zinc at a flow-through porous electrode
in light of a mathematical model which was presented in Part I. The pr
ocess is accompanied by simultaneous hydrogen evolution within the ele
ctrode, which increases the pore electrolyte resistivity and decreases
the coulombic efficiency. We measured polarization curves, coulombic
efficiencies, and current distributions under various conditions of zi
ncate concentrations, flow rates, cell current, and electrode thicknes
s. Reasonable agreement between the measured and predicted current dis
tributions was obtained only under conditions of high electrolyte flow
rates, low cell currents, and thinner electrodes. The deviations obse
rved at low electrolyte flow rates and high cell currents are attribut
ed to the agitating effects of the hydrogen gas bubbles, which enhance
the local mass-transfer coefficient. This effect was not incorporated
in the model due to the absence of adequate correlations.