Recovery of metallic copper by integrated chemical reduction and high gradient magnetic separation

Abstract

The recovery of metals from waste effluents is necessary for pollution prevention and sustainable practice. High gradient magnetic separation (HGMS) is seen as a viable method. We investigated the capture of valence copper from aqueous copper ion by HGMS in combination with a chemical reduction process. When a copper solution (3.9 or 15.6 mM) was exposed to excess of dithionite (mole ratio of 1:3) in the presence of ammonia (mole ratio of 4) and amended with MnCl₂ (2.5 g/L) and the mixture passed through a flow reactor under a strong magnetic field (10000 Gauss), valence copper was obtained and captured in the reactor with well over 95% yields. The chemical reduction reactions were unaffected by the presence of MnCl₂ while the amount of MnCl₂ (0, 20 and 32 mM) has significantly varied the copper recovery efficiency, especially in the case of high initial copper ion concentration (15.6 mM). Formation of MnO₂ flocs was found to have a detrimental effect on copper removal efficiency. The HGMS method offers a tool of resource recovery for copper from waste effluents.

Keywords:

• high gradient magnetic separation
• copper
• chemical reduction