Characterisation and recovery of non-ferrous metals met in a copper-slag processed by flotation

Detailed process oriented characterisation on representative samples from plant survey of the slag
flotation plant belonging to Aurubis, Bulgaria has been realised in order to evaluate the mineralogical
occurrences of Cu, Ni, Mo and Co bearing phases. The slag subjected to flotation consisted in majority
of fayalite, magnetite-iron oxides and a glass-like phase. Ni and Mo have been found to be closely
associated to magnetite and fayalite. The tailing from the slag flotation has been subjected to sulphation
roasting followed by water leaching as a hydrometallurgical means to recover the remaining Cu, Mo,
Ni and Co. Based on the various sulphation roasting conditions (acid dosage, duration, temperature)
copper, nickel and cobalt were brought to solution to a different extent. Molybdenum was the most
difficult to be rendered soluble due to its close association with iron, suspected to form an insoluble
compound with it. Sulphation roasting performed at 350ºC has secured the best extraction degree for
Cu, Mo and Co, while maximum recovery of Ni has been documented when roasting was done at 150°C.