Effect of oxygen and sodium sulfide on flotation of cuprite and its modification mechanism

Effect of oxygen and Na2S on the flotation of cuprite was invested by flotation test, FESEM, EMPA and XPS. The micro-flotation experiments indicated that the flotation recovery of cuprite can be greatly increased by adding an appropriate amount of Na2S. FESEM showed that numerous fragments were covered on the cuprite surfaces after sulfidization, and the shapes of these fragments were more regular and complete with the Na2S concentration of 5.0x10-4 mol/L. EPMA and EDS analysis confirmed that these fragments were newly-formed copper sulfide species, which was the key to promoting the flotation of cuprite. XPS analysis revealed that the sulfidization process of cuprite was that Na2S first underwent an oxidation-reduction reaction with the CuO on its surface, which was due to the extremely easy oxidation of the surface of cuprite. The Cu2+ was reduced to Cu+, and S2- was mainly oxidized to (S2)2- and (Sn)2-.