Surface properties and flotation inhibition mechanism of air oxidation on pyrite and arsenopyrite

• The oxidation and floatability of pyrite and arsenopyrite in air was studied. • The oxidation products change the surface morphology of both minerals. • Pyrite and arsenopyrite have similar surface atomic arrangements. • Hydroxyiron compounds are stably adsorbed on the surface. • The hydroxyl iron on the surface prevents the adsorption of xanthates. It is critical to study the surface properties of pyrite and arsenopyrite by oxidation and its effect on flotation behavior. The recovery of pyrite and arsenopyrite reduced with increasing pH but remained flotation-competent, whereas both minerals were non-flotation-competent after oxidation at pH > 6. XPS revealed that the surface of oxidized pyrite was rich in SO2- 4 and FeOOH, but arsenopyrite had some FeAsO 4 in addition to these two oxidation products, and arsenopyrite showed a higher oxidation degree than pyrite for same oxidation period. In the AFM scan results, the roughness of the oxidized pyrite surface and the distribution rate of oxidation products were lower than in arsenopyrite. Calculation results showed that the most stable surfaces of pyrite and arsenopyrite were S-exposed surfaces with similar S-atom arrangement patterns. The bonding between Fe(OH)- 2, the main component of the oxidation products at pH = 6, and Fe atoms on the surfaces of pyrite and arsenopyrite, as well as the exothermic and favourable adsorption process, indicated that oxidised mineral surfaces adsorbed large amounts of hydroxylated iron compounds, and thus the trap xanthic acid appeared to be unable to adsorb on the oxidised surfaces. This study adds to our understanding of the surface oxidation of pyrite and arsenopyrite and the mechanisms by which they affect flotation behaviour.