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 (PCO2 = 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.