Direct copper electrowinning from iron-rich e-waste leachates without prior iron removal

Electronic waste bioleaching generates leachates rich in copper and ferrous iron, which conventionally require iron removal before copper electrowinning because Fe²⁺ impairs current efficiency and deposit purity. A systematic investigation confirmed that direct-current electrowinning of copper from such iron-rich leachates is feasible without any iron-removal step, thereby simplifying the hydrometallurgical process. Key operational parameters (0 – 26.4 g L⁻¹ Fe²⁺, 5 – 15 g L⁻¹ Cu²⁺, current density 25 – 275 A m², temperature 25 – 55 °C, flow rate 1 – 3 min⁻¹) were systematically varied in a Taguchi design to assess their effects on copper deposition rate, current efficiency, deposit morphology, and cathode purity. Increasing Fe²⁺ content drastically lowered current efficiency (from 80 – 95% to 15 – 60%) and slowed the copper deposition rate. However, high copper purity (≈ 99.9%) and a uniform sheet morphology were preserved as long as continuous cathode sheet growth was favored. A predictive model was developed to define the operating boundaries for copper sheet formation as a function of current density and Cu²⁺ concentration, and it was experimentally validated. In a 25 L pilot electrowinning test, 100% cathode sheet coverage was achieved at 75 A m⁻² and 25 °C using a leachate containing 15 g L⁻¹ Cu²⁺ and 26.4 g L Fe²⁺, yielding a deposit with 99.9% Cu purity and only 0.01% Fe. These results confirm that high-purity copper can be directly electrowon from highly ferrous solutions under optimized low-current-density conditions. By eliminating the iron-removal step, this approach significantly simplifies the hydrometallurgical process.