The flotation separation of molybdenite from chalcopyrite using a polymer depressant and insights to its adsorption mechanism

[Display omitted] •A PAM-ATU polymer was introduced as the chalcopyrite depressant.•PAM-ATU showed a stronger depressing power to chalcopyrite than TGA.•A good separation efficiency was achieved when using diesel collector.•PAM-ATU chemisorbed on chalcopyrite surface via Cu sites and thiourea groups. In the present study, the poly(acrylamide-allyl thiourea) (PAM-ATU) with an average molecular weight of approximately 1.66 × 104 g/mol was introduced as the chalcopyrite depressant in the flotation separation of molybdenite and chalcopyrite. The effects of PAM-ATU on their flotation performances were evaluated by micro-flotation and bench-scale experiments, and its adsorption mechanism to chalcopyrite was investigated by Fourier transform infrared spectroscopy (FT-IR), zeta potential tests and X-ray Photoelectron Spectroscopy (XPS) measurements. The flotation experiments results demonstrated that PAM-ATU had a stronger depressing ability than the conventional depressant thioglycolic acid (TGA) for chalcopyrite. At pH around 10.5, a good separation efficiency for artificially mixed minerals could be achieved with a 78.2% Mo recovery and a 58.9% Mo grade in the froth products, in which, the Cu grade was only 1.68%. It was also found that nearly 80.0% of Cu was depressed effectively with 150 g/t PAM-ATU after one rougher flotation in bench-scale experiments with a Mo recovery of almost 80.0%. FT-IR, zeta potential tests and XPS analysis results provided strong evidence that PAM-ATU could adsorb on chalcopyrite surface. Further, FT-IR and XPS analysis suggested that PAM-ATU might mainly chemisorb on chalcopyrite via Cu sites on surface through S and N atoms in PAM-ATU polymer. This study indicated that the synthesized PAM-ATU polymer with low molecular weight could be a promising depressant for chalcopyrite in the flotation separation of Cu-Mo ores.