The behaviour of lead in anode during electrolysis was investigated in terms of impurity level in anode and concentration of dissolved oxygen and H₂SO₄ in electrolyte.
The metallic granular forms of lead were found in the anode at the lower lead level of less than 5, 000 ppm. However, the higher lead level anode exhibited a mesh-like shape in copper matrix. The anode potential-time curves show discontinuous steps based on the falling of slime from anode surface during electrolysis, and then the passivation were not observed. The slimes obtained in this work were falling and adhering slimes. The adhering slimes were dark-brown color mostly consisted of PbSO₄and copper powder. The ratio of PbSO₄to copper powder in the adhering slimes increased with increasing lead level in anode, and it ranged 50-80 wt%. The PbSO₄characteristically deposited around the undissolved metallic lead. This is because the lead was dissolved in the electrolyte and immediately reacted with SO₄ions in electrolyte to form PbSO₄.
On the electrolysis with the Cu-As-Pb-O anode composition of slime obtained was mainly shown to be PbSO₄and Cu₃As. Trace amount of As₂0₃and PbO were detected in the slime. Undissolved lead was also present in it.