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. In the present paper, effects of the concentrations of Cu2+ (10–50 g/L), Zn2+ (0–40 g/L) and free H2SO4 (1–5 N) in the electrolyte as well as cathodic current density (50–350 A/m2) and bath temperature (30–70 °C) have been studied on the macroscopic surface quality of copper deposits defined by their visual morphological characteristics as expressed by an innovative Deposit Morphology Index (DMI). A Central Composite Design of experiments has been used to develop a quadratic model correlating the key operating parameters to the DMI. Statistical analysis of the experimental results showed that the concentration of Cu2+ in the electrolyte and the cathodic current density are the most influential factors on the quality of the deposits. It was also found that these two parameters have statistically significant interaction on each other. A smooth and compact copper deposit could be obtained at high Cu2+ concentrations and high current densities (above 40 g/L and 250 A/m2, respectively) regardless of the level of other factors. However, when the electrolyte temperature is relatively high (60 °C), the optimum condition extends to low current densities (down to 50 A/m2) and mid Cu2+ concentrations (30–40 g/L).

Graphical AbstractFigure optionsDownload as PowerPoint slideHighlights
► Acceptable copper cathodes can be obtained via direct electrowinning of brass scrap.
► An innovative index was devised to quantify the surface quality of cathode product for modeling.
► Surface quality was mostly influenced by Cu2+ concentration and current density.
► Electrolyte temperature was found less influential, while H2SO4 concentration insignificant.
► Compact and smooth copper deposits were obtained despite high Zn2+ content in the electrolyte.