Application and electrochemical depression mechanism of sodium sulfite on the flotation separation of galena–pyrite mixed concentrate in Yiliang typical high‑sulfur lead–zinc deposit

The high content of pyrite in high‑sulfur lead–zinc sulfide resources affects the electrochemical properties and floatability of galena and sphalerite, which results in difficult flotation separation. In this study, the negative effects of a high-alkaline process were weakened by introducing an efficient mixed depressant CaO + Na₂SO₃ in selective flotation separation of galena from pyrite. Flotation separation tests of real ore samples showed that the mixed depressant was more efficient than single CaO (5000 g/t), and the best process conditions of Pb grade 64.01 % and Pb recovery 88.45 % were obtained. The effects of Na₂SO₃ on the electrochemical interaction between the two minerals were studied by micro-flotation tests, electrochemical, ion dissolution, UV–Vis measurements, zeta potential measurements, and X-ray photoelectron spectroscopy (XPS) detections. Results indicated that Na₂SO₃ could weaken the galvanic interaction between galena–pyrite and reduce the Pb²⁺ dissolution from the galena surface. Na₂SO₃ could desorb the collector ethyl xanthate pre-adsorbed on the pyrite surface.