Copper electrowinning from dilute cyanide solution in a membrane cell using graphite felt

The direct electrowinning of copper from dilute cyanide solutions was conducted in a membrane cell using graphite felt. The accumulation of deposited copper on the graphite felt as the plating proceeds significantly improves the conductivity of the graphite felt, increases the specific surface area and benefits copper deposition. The deposition current efficiency decreases with the increasing CN/Cu mole ratio. Copper can be deposited efficiently on the graphite felt from low concentration solutions (1–2 g L−1 Cu and CN/Cu mole ratio=3–9) with 50–80% current efficiency and with the removal of around 40% Cu. The energy consumption was 1–2 kW h/kg Cu in the current superficial density range 30–100 A m−2 at ambient temperature.