Pyrite cinder (PyC) containing polymetallics is difficult
to use
due to the low grade of metals and complex mineral phase composition,
the low reutilized rate of which causes the wastage of resources.
In this paper, a novel approach based on mineral phase reconstruction
was proposed to recover Cu, Co, and Fe from PyC. A feasible reduction
roasting process was developed for mineral phase reconstruction, followed
by leaching with sulfuric acid to recover Cu and Co; finally, the
leaching residue was separated by a magnetic tube to recover Fe. The
maximum copper and cobalt extract rates of 86.15 and 79.61% were achieved
respectively under the optimized conditions of reduction roasting
for 30 min at 550 °C and 30% CO/N2 volume fraction,
followed by leaching for 4 h at a liquid–solid ratio of 4:1
(mL/g), a mass concentration of 160 g/L sulfuric acid, and a temperature
of 70 °C. The iron concentrate can be obtained with 63.08% Fe
grade and 98.91% recovery rate by magnetic separation at a magnetic
field strength of 28.26 kA/m. The mechanism analysis results of mineral
phase reconstruction revealed that the primary copper sulfide in PyC
was transformed into free copper oxide, combined copper oxide, and
secondary copper sulfide without changing the valence state of copper
by reduction roasting, resulting in a higher extraction rate of copper.
Meanwhile, cobaltosic oxide and cobalt ferrite in PyC were transformed
into cobalt sulfate and cobalt sulfide with the reduction of Co(III)
to Co(II), improving the extraction rate of cobalt.