Integrated conversion of β-spodumene into Li4SiO4-based sorbents for high-temperature CO2 capture

Li 4 SiO 4 -based sorbents are promising candidates for high-temperature CO 2 capture, but their conventional synthesis usually requires separately supplied lithium and silicon precursors, limiting resource efficiency. Herein, an integrated strategy was proposed to convert β-spodumene into Li 4 SiO 4 -based CO 2 sorbents by coupling lithium recovery with the utilization of silicon-rich extraction residues. Three lithium extraction methods using NaOH, CaCl 2 , and Na 2 CO 3 were evaluated at different Na/Ca:Li molar ratios, with 2:1 identified as a suitable ratio for balancing lithium recovery and impurity control. The recovered Li 2 CO 3 precursors were then used to synthesize Li 4 SiO 4 -based sorbents with fumed silica, among which the Na 2 CO 3 -derived Li 4 SiO 4 -NC2 exhibited the best CO 2 sorption performance, achieving 0.28 g/g at 620 °C over 20 cycles. Together with its 90.3% lithium recovery, the Na 2 CO 3 route was identified as the optimal extraction pathway in this work. The silicon-rich lithium slag from the same route was further adopted as an alternative silicon source, used directly or after water/acid washing. Li 4 SiO 4 -LAL prepared from acid-washed lithium slag reached the highest CO 2 uptake of 0.31 g/g at 620 °C over 20 cycles, outperforming the fumed-silica-derived reference, although with slightly lower cyclic stability. Structure-performance analysis indicated that surface morphology mainly controlled CO 2 uptake, whereas pore structure was more closely related to cyclic stability in Li 4 SiO 4 -based sorbents. This work demonstrates a practical pathway for integrating lithium recovery and silicon-rich residue utilization into the preparation of mineral-derived Li 4 SiO 4 -based sorbents for high-temperature CO 2 capture.