A novel porous Pb–Ag anode for energy-saving in zinc electro-winning: Part I: Laboratory preparation and properties

A novel porous Pb–Ag (0.8wt.%) anode was investigated for zinc electro-winning and six kinds of porous anodes with different controlled pore size and homogeneous pore structure were prepared by negative pressure infiltration. Their electrochemical properties were studied by chrono-potentiometry in the electrolyte of ZnSO4–H2SO4 and ZnSO4–MnSO4–H2SO4, respectively, and the results compared with the traditional flat plate anode. The results show that with the decrease of pore size, the anodic potential first decreases and then increases in ZnSO4–H2SO4 electrolyte. The lowest value was 1.729 V when the pore size was 1.25–1.60 mm, which is 106 mV lower than that of the flat plate anode. The anodic corrosion rate reaches the lowest value at the pore size of 1.60–2.00 mm. In the electrolyte of ZnSO4–MnSO4–H2SO4, the formation of dense PbO2/MnO2 protective layer leads to a further decrease of the anodic potential and corrosion rate while manganese impurity has little effect on cathode current efficiency. Furthermore, the porous anode is beneficial in decreasing the precipitation of Mn2+ from solution as MnO2. Compared with the flat plate anode, the behavior of the porous anode is similar to a flat plate anode operating under a lower current density.