What Anodes are Used for Electrowinning of Metals

What Anodes are Used for Electrowinning of Metals?

The anode material in the electrowinning of metals from sulfuric acid solution has traditionally been lead because of its high corrosion resistance. During use, the lead surface is oxidized resulting in an electrochemically active PbO2 layer. This layer prevents further oxidation and provides an electrochemically active and conductive material passing the anodic current.

Most of the oxygen evolving anodes for electrowinning have focused on lead anodes since 1990s. Electrowinning from chloride-based solutions is primarily used at certain plants to recover nickel, cobalt, and copper. In these electrolytes, lead-based anodes are not as efficient as in sulfuric acid solutions. The anodes are usually different metal oxide anodes.

The mixed metal oxide anodes are more energy-efficient than lead anodes. The operation of lead anodes is well known as they have been used for decades. The activity and operating time of the oxide anodes in sulfate-based electrolytes is still an open question. IrO2-Ta2O5 coated titanium anode has been used in sulfuric acid solutions for electrowinning of copper, nickel, zinc, and iron.