Lithium based high temperature sorbent from copper slag: Synthesis and CO2 capture performance

Using high temperature CO2 sorbent for carbon capture is an effective approach to reduce carbon footprint. Copper slag, as an abundant metallurgical waste containing substantial amount of Si and Fe resources, was being explored as cheap raw material for the preparation of lithium-based sorbent. The results shows that the lithiation is initiated at 450–600 °C, where fayalite and magnetite in slag are firstly oxidized by released water vapor from the decomposition of LiOH, then further react with Li2O to form Li4SiO4 and LiFeO2. As the temperature rises, the conversion of LiFeO2 to Li5FeO4 and incorporation of Fe3+, Al3+ into Li4SiO4 lattice occur in parallel. The resulting sorbent exhibited excellent CO2 chemisorption ability with a capture capacity of 420 mg/gmaterial at 725 °C. Particularly, even in the gas stream containing 5 vol% CO2, it showed a CO2 uptake capacity of 383 mg/gmaterial. In the CO2 cycling tests, the sorbent suffered a decay in sorption capacity, which was ascribed to the poor regeneration ability of Li5FeO4. Comparatively, it possesses a relatively high capacity of 241 mg/gmaterial in 20 vol% CO2 after 20 cycles, which is higher than those of previously reported Li-silicate sorbents derived from wastes.