Phase-Controlled Oxidation Modification for Simultaneous Recovery of Iron and Silicon from Copper Slag: Mechanism and Process Optimization

With the increasing depletion of mineral resources and growing environmental pressures, the resource utilization of industrial solid waste has become crucial for sustainable development. Aiming at copper slag, a typical metallurgical solid waste, a phase-controlled oxidation modification method using CaO-MgO as modifier under high temperature was proposed in this study, which realized the efficient separation and recovery of iron and silicon resources. Through the systematic investigation of key parameters including oxidation temperature, basicity, and holding time, combined with characterization techniques such as XRF, XRD, SEM-EDS, and XPS, the phase transformation mechanism during the oxidation modification process was elucidated. The results showed that the basicity determined the presence form of iron and silicon, the temperature regulated the ion diffusion conditions, and the holding time affected the crystalline integrity of (Mg,Fe 2+ )Fe 2 O 4 . Under optimal conditions (oxidation temperature: 1300 °C, basicity: 2.0, holding time: 60 min), the iron element was effectively enriched to (Mg,Fe 2+ )Fe 2 O 4 and silicon element was converted to Ca 2 SiO 4 , forming distinct phase boundaries favorable for separation. After magnetic separation, the iron recovery rate was 85.83%, the total iron of the concentrate was 46.18%, and the content of Si, P, and S was reduced. The concentrate is suitable for direct recycling as ironmaking raw material in steel plants, and the Ca 2 SiO 4 -rich tailings can be utilized as construction materials to achieve synergistic "waste reduction-resource recovery" treatment of copper slag. This study provides new insights for high value utilization of metallurgical wastes, while offering practical solutions to alleviate resource pressures and environmental risks.