Valorization of Metallurgical Slags into High-Performance Lithium Ferrite for Efficient CO₂ Capture

Copper slag was used as a raw material to prepare lithium ferrite by the solid-state reaction method at different Li:Fe molar ratios. The obtained materials were characterized by XRD, SEM, and N₂ adsorption-desorption, and their CO₂ capture behavior was evaluated using thermogravimetric and temperature-programmed techniques. A 7:1 Li:Fe molar ratio allowed to obtain Li₅FeO₄, as well as Li₄SiO₄, due to the high silicon content in the slag. CO₂ sorption tests showed that, as temperature increases, CO₂ capture increases up to 675 °C. Slag-ferrite achieved a maximum CO₂ capture of 20 wt% at 675 °C (P_CO2 = 0.2), equivalent to 62.5% of the CO₂ sorption of reagent-grade ferrite (32 wt%). Kinetic analysis of CO₂ capture using the Avrami-Erofeev model indicated that bulk diffusion is the rate-controlling step. These results provide quantitative evidence on the use of copper slag in the preparation of lithium ferrites, with potential application in a high-temperature CO₂ capture process.