Processes during the electrorefining and electrowinning of lead

The anodic and cathodic processes in the fluorosilicate electrolytes during galvanostatic deposition under (DC) and polarity reversal current (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 the 95 h operation cycle, a limiting anodic polarization barrier value ( Δϕ Acr = 200 mV) is attained. In this case bismuth and antimony start to dissolve actively from the anodes and are deposited onto the cathode, while under PRC conditions Δϕ Acr is not reached even after 95 h. The cathodic deposits are rounded crystal grains and display pronounced epitaxial growth. Spectral analysis shows that Sb is the main impurity of cathodic lead instead of Bi. During the electrowinning of the lead, without using H 3PO 4 as an inhibitor of β-PbO 2 parasitic deposition onto the inert graphite anodes, it was established that a critical value of the anodic potential ϕ Acr = 1430–1500 mV/SCE) exists, under which β-PbO 2 is not deposited. If H 3PO 4 is present, β-PbO 2 is not deposited onto the graphite anodes at any values of the anodic potential.