Synergistic effects of ultrasonication on the flotation separation of galena from chalcopyrite using sulfuric acid as a depressant

The flotation separation of galena (PbS) and chalcopyrite (CuFeS2) with sulfuric acid (H2SO4) requires high temperatures (60-80 degrees C) and long treatment times (greater than25 min). In this paper, ultrasonication was applied to enhance PbS depression with H2SO4. Flotation and contact angle results revealed that PbS rather than CuFeS2 could be completely depressed by H2SO4 and ultrasonication without slurry heating. The reaction time for PbS depression could be shortened to 6 min. The synergistic effect of ultrasound occurred mainly due to the hot spots on the PbS surface, which introduced high levels of heat on the PbS surface. This ultrasound-assisted treatment produced PbSO4 species that coated the whole PbS surface and reduced its hydrophobicity. In contrast, new hydrophilic components barely formed on the CuFeS2 surface after ultrasonication. Therefore, the CuFeS2 remained hydrophobic and could be floated by air bubbles. These findings implied that ultrasound exhibited obvious synergistic effects on PbS depression using H2SO4. Therefore, the separation of PbS and CuFeS2 could be achieved in a short time. This work provided an energy-saving technique for separating PbS from CuFeS2.