Purification of Cu–Zn melt based on the migration behavior of lead and bismuth under pulsed electric current

Abstract

The recovery and regeneration of waste brass can alleviate the pressure of ore resource demand, and can also obtain considerable economic profits from the regenerated alloy products. However, excessive lead and bismuth residues in brass will lead to severe high temperature brittleness of the alloy, and chemical separation will complicate the separation process due to the difference in activity between elements. In this study, the physical separation of Pb and Bi from brass was realized by applying pulse current based on the electrical conductivity difference between Pb, Bi and brass melt, overcoming the limitation of using metal activity difference for oxidation refining. For 10 kg melt, the distribution of current line is adjusted by designing current intensity, frequency and electrode position to explore the migration behavior of Pb and Bi in brass melt under the action of pulse current. After pulse current treatment, Pb and Bi accumulate on the surface of the melt, especially at the bottom of the melt, forming a region rich in Pb or Bi. Based on the numerical calculation, Pb and Bi migrate in the direction perpendicular to the current line driven by the current density gradient, and the migration direction is the direction of the current density gradient decreasing. Pulse current separation technology has the characteristics of shortening the recovery steps, green energy saving, which provides a new solution for the difficult recycling of scrap copper and has great commercial value.