PROCESSES DURING THE ELECTROREFINING AND ELECTROWINNING OF LEAD

The anodic and cathodic processes in the fluorosilicate electrolytes d uring galvanostatic deposition under (DC) and polarity reversal curren t (PRC) regimes were investigated. It was established that, during the process of lead electrorefining from concentrated electrolyte without applying PRC, at c.d. i = 300 A/m(2) (3 A/dm(2)), after 60-80 h of th e 95 h operation cycle, a limiting anodic polarization barrier value ( Delta phi(A)cr = 200 mV) is attained. In this case bismuth and antimon y start to dissolve actively from the anodes and are deposited onto th e cathode, while under PRC conditions Delta phi(A)cr is not reached ev en after 95 h. The cathodic deposits are rounded crystal grains and di splay pronounced epitaxial growth. Spectral analysis shows that Sb is the main impurity of cathodic lead instead of Bi. During the electrowi nning of the lead, without using H3PO4 as an inhibitor of beta-PbO2 pa rasitic deposition onto the inert graphite anodes, it was established that a critical value of the anodic potential phi(A)cr = 1430-1500 mV/ SCE) exists, under which beta-PbO2 is not deposited. If H3PO4 is prese nt, beta-PbO2 is not deposited onto the graphite anodes at any values of the anodic potential.