Density Tuning in Conjunction with Pelletizing of Reductants for Enhanced Recovery from Copper Smelting Slag

High-efficiency reduction of Fe 3 O 4 particles in molten copper slag is the key for recovering slag-entrained copper, although restrained by the sluggish reaction kinetics of commercial powdery reductants with low density. Here, a new strategy by density tuning in conjunction with pelletizing of the powdery reductants is suggested, greatly enhancing the Fe 3 O 4 reduction kinetics and resulting in remarkably facilitating the recovery of slag-entrained copper. Specifically, by replacing the industrially used coal powder with FeS 2 -C pellets at optimized density, the efficiency of Fe 3 O 4 reduction is significantly increased from 18% to 51%, with the copper content in the low-layer slag being correspondingly enriched from 1.37% to 4.53%. The SEM-EDS characterizations and finite element analytical results all reveal that the enhanced reduction of Fe 3 O 4 by the as-designed reductant contributes to the decrease of slag viscosity and copper exposure, as well as to the size growth of copper matte droplets, resulting in promoted settling of copper-containing components for copper–slag separation in the molten state. Additionally, the full exposure and size growth of copper matte in the molten state facilitate copper reclamation during the subsequent grinding–flotation process of the solidified slag, which increases the copper recovery from 23.3% to 85.3%, with the concentrate grade being correspondingly improved from 2.8% to 6.45% after one-stage flotation. The results can provide new insights into enhancing the recovery of slag-entrained copper.