Fabrication of lithium silicate sorbents from dual waste precursors: Recycled lithium and glass powder for carbon dioxide capture.

Carbon capture and storage (CCS) is a vital strategy for mitigating global climate change, with the development of efficient and low-cost carbon dioxide (CO2) sorbents being central to its widespread implementation. Although lithium silicate (Li4SiO4) exhibits excellent cyclic stability as a high-temperature CO2 sorbent, its large-scale application is limited by the high cost of lithium precursors. This work proposes the low-cost strategy for CO2 capture by synthesizing Li4SiO4-based sorbents using spent LiMn2O4 batteries and waste glass powder. Four Li4SiO4 sorbents were synthesized using Li2CO3 extracted from spent LiMn2O4 batteries and waste glass powder. One sorbent was prepared with untreated glass powder at a Li2CO3/SiO2 molar ratio of 4.1:1 (L-UG1), while the other three were obtained from pre-treated glass powder with molar ratios of 4.1:1(L-ACG1), 5:1 (L-ACG2), and 6:1 (L-ACG3), respectively. Among them, L-ACG1 exhibited the best performance, achieving a stable CO2 uptake of 0.30 g/g over 20 cycles at 600 °C under 15vol%CO2. Kinetic analysis revealed that although L-UG1 had the lowest activation enthalpy, its uptake was limited by the formation of inactive Na2Si2O5. In contrast, L-ACG1 showed improved Li4SiO4 phase purity, higher CO2 uptake, and structural stability, largely due to the formation of LiAlO2, as confirmed by in situ X-ray diffraction (XRD) and situ Raman spectroscopy. Moreover, economic analysis showed that the cost of synthesizing L-ACG1 was only one-sixth that of commercial precursors, highlighting its industrial viability. These findings demonstrate a sustainable and effective strategy for CO2 capture by valorizing spent LiMn2O4 batteries and waste glass, and underscore the importance of precisely controlling the Li/Si ratio and impurity content during synthesis.