SIMULTANEOUS ELECTRODEPOSITION OF LEAD AND LEAD DIOX

Results are reported of experiments and model领 of cathodic Pb and anodic PbO2 electrodeposition, aimed at developing a process using both reactions simultaneously for treating aqueous effluents from lead-acid battery plants. Pb(II) solubilities and equilibrium potentials were calculated as functions of pH and sulfate activities. Using kinetic parameters from the literature or determined experimentally, (illustrative) models were developed for current density-potential and current efficiency-potential relationships, together with the current density dependence of specific electrical energy consumptions for Pb(II) recovery. Experimental current density-potential and charge efficiency-potential relationships were in broad agreement with model predictions, with near unity current efficiencies for mass transport controlled PbO2 deposition from electrolytes containing 1 mol Pb(II) m-3 at pH 0.7 or 12. However, charge efficiencies for cathodic deposition of lead were typically 0.2 for 1 mol Pb(II) m-3 + 1 mol O2 (aq) m-3; removal of dissolved oxygen was predicted and determined to increase current efficiencies to near unity. Simultaneous cathodic Pb and anodic PbO2 electrodeposition was predicted to be feasible, with tight control of current densities being required to minimise specific electrical energy consumptions.