Sorption of CO2 on NaBr co-doped Li4SiO4 ceramics: Structural and kinetic analysis
Structurally modified and improved NaBr-co-doped Li 4 SiO 4 ceramics were developed for CO 2 absorption in low-CO 2 -concentration atmospheres. Pure and NaCl-doped Li 4 SiO 4 ceramics were also prepared for comparison. The samples were analyzed by X-ray diffraction, Scanning Electron Microscopy, N 2 adsorption, X-ray photoelectron spectroscopy, differential scanning calorimetry , and thermogravimetric analyses (dynamic and isothermal). The sorption kinetics were obtained using a double exponential model. The results showed that both Na and Br can be introduced into the Li 4 SiO 4 structure and doped on Li and oxygen sites, respectively. The doped sample presented a Li 2 O-enriched surface, guaranteeing abundant Li O sites and are significantly different from previous anionic (CO 3 , F and Cl) doping of Li 4 SiO 4 , Br doping also generated macroporous features with small particle size, these favorable characteristics promoted the surface chemisorption kinetics. Moreover, DSC analysis confirmed the formation of the molten phases during CO 2 absorption, which helps improve the lithium diffusion kinetics . Here, 0.1 mol NaBr doping was used to reach a maximum absorption capacity (>30.0 wt%) in 15 vol% CO 2, suggesting that NaBr-doped Li 4 SiO 4 ceramics have great potential for CO 2 capture at high temperature.
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