Migration and Substitution Mechanism of Lead at the Matte–Slag Interface During Matte Converting

The migration of Pb in matte–slag interface and substitution behavior in slag are crucial for its efficient removal and solidification during copper smelting. This study investigated the migration behavior of PbS/PbO in matte–slag interface and substitution mechanism of PbO in fayalite. The results show that PbS is primarily incorporated into matte by forming solid solutions with Cu 5 FeS 4 and Cu 2 S. The enhanced interaction between PbS and FeO with rising temperature increases the Pb content in slag from 7.86 pct at 1100 °C to 9.66 pct at 1250 °C. Decreasing the Fe/SiO 2 of slag from 2.2 to 1.6 lowers PbO activity in slag, thereby increasing the Pb content in the migrated slag from 8.46 to 16.09 pct. While PbO migrates into slag for its higher solubility in oxide-based slag and combines with silicates such as fayalite. Regarding the substitution mechanism, the unit cell volume of Fe 2 SiO 4 decreases from 308.45 to 307.55 Å 3 with increasing PbO addition from 0 to 15 pct revealing the destructive role of PbO on the crystal structure. Mossbauer spectroscopy reveals that the Pb 2+ provided by PbO substitute for Fe (M2 sites) in the octahedral crystal structure of fayalite, resulting in lattice structural changes and forming Fe 2− x Pb x SiO 4 . The Fe 2+ released from the substitution is incorporated into Fe 3 O 4 along with O 2− from PbO and original Fe 3+ . The findings provide a theoretical basis for achieving Pb targeted removal and reducing environmental pollution, and offer insights for unstable Pb‑bearing phases solidification during copper slag resource recycling.