Flotation of auriferous arsenopyrite from pyrite using thionocarbamate

To provide an understanding of the preferential interaction and flotation of Cu-activated arsenopyrite compared to pyrite, Cu species adsorbed, extent of surface oxidation, nature of bond and coordination between donor atoms of IPETC, and Cu and As acceptor atoms on mineral surfaces was investigated using X-ray photoelectrons spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analysis. Adsorption of Cu (II) and concurrent reduction to Cu(I) ions, which was paramount for the formation Cu-IPETC chelate complex was apparent on the surface of both pyrite and arsenopyrite from the XPS analysis. IPETC adsorption did not lead to removal of surface oxidation product on either pyrite or arsenopyrite surface, with extent of ferric hydroxide coverage on arsenopyrite far exceling that of pyrite. Adsorbed Cu(I) on the surface of pyrite was higher than arsenopyrite and was irreconcilable to their flotation performance. Bonding of S occurred with Cu(I), and As coordination with deprotonated N was suggested with the strength of the bond increasing at pH 11 using enargite as surrogate mineral. Roughing and single stage flotation of a refractory ore using 200 mg/l CuSO4 and 300 mg/l IPETC at pH 11 gave an Au and As grade of 26.2 g/t and 1.35% respectively, at a mass pull of 6.9 wt% and 82.2% Au recovery.