Adherent anode slimes can cause anode passivation in copper electrorefining and lower the efficiency of copper electrorefining. Declining concentrate grades cause larger impurity levels in anodes, thus creating larger quantities of slimes in the refining process. In order to investigate the characterization methods for adherent anode slimes in copper electrorefining, experiments were conducted for the Boliden Harjavalta Pori refinery material. Methods such as particle size determination, chemical (ICP) analysis, settling rate determination, XRD, SEM-SE, SEM-BSE and SEM-EDS were applied. In addition, adherent anode slime samples were compared to optical micrograph and SEM-BSE images of respective anode copper samples. It was shown that SEM-EDS and SEM-BSE provided precise information about phases formed during electrorefining. The settling rate and particle size had a correlation only with a copper content of anode slime. The main phases in the anode slime were copper and lead sulphates as well as copper-silver selenides. NiO was shown to be the major Ni-bearing phase in the adherent slime. Nickel, tellurium and lead had the strongest, whereas arsenic, selenium and antimony had the weakest tendency to report to the anode slime.

Peer reviewed