Modeling and optimization of surface quality of copper deposits recovered from brass scrap by direct electrowinning

A research study has been undertaken to develop the fundamentals of a method for the direct recovery of copper from brass (Cu–30 wt.% Zn) scrap based on simultaneous electrolytic dissolution of the scrap at the anode and electrodeposition of copper at the cathode in an acidified sulfate electrolyte. The objective was to explore the effects of key factors such as concentrations of Cu2+ (10–50 g/L), Zn2+ (0–40 g/L) and free H2SO4 (1–5 N), cathodic current density (50–350 A/m2), and bath temperature (30–70 °C) on the surface quality of copper deposits. A Central Composite Design was applied to create a quadratic model correlating the operating parameters to the Deposit Morphology Index (DMI). The statistical analysis revealed that the concentration of Cu2+ and cathodic current density were the most influential factors impacting the deposit quality. It was found that optimal conditions for a smooth and compact copper deposit were achieved at high Cu2+ concentrations (above 40 g/L) and current densities (over 250 A/m2). However, with elevated electrolyte temperatures (60 °C), optimum conditions shifted to lower current densities (down to 50 A/m2) and mid-range Cu2+ levels (30–40 g/L).