High-temperature capture of CO2 by Li4SiO4 prepared with blast furnace slag and kinetic analysis

Blast furnace slag was leached using HCl to prepare lithium-based sorbents for CO2 capture, and chemical composition and phase of the acid leaching slag were determined by X-ray fluorescence analysis. The microstructure and morphology of both sorbents were characterized by scanning electron microscope and X-ray diffraction. The absorption capacity of both sorbents was observed non-isothermally and isothermally using thermogravimetric analysis, and 12 carbonation and calcination cycles were conducted to observe cycling stability. Controlling step of absorption process was determined by fitting the isothermal graphs using a double exponential model. The results show that 98.33% amorphous SiO2 can be obtained when the blast furnace slag was treated at 373 K for 10 h. Purified lithium-based sorbent by acid leaching slag (LBS-ALS) shows dense polyhedral particles with particle size between 25 and 120 mu m. LBS-ALS shows similar absorption capacity with pure Li4SiO4 (P-Li4SiO4), but narrower absorption temperature range at non-isothermal absorption condition. The double exponential model fits well with the isothermal graphs for LBS-ALS and P-Li4SiO4, and diffusion of CO2 is the controlling step of the absorption process at lower temperature. LBS-ALS shows different controlling mechanism for desorption process compared with P-Li4SiO4. LBS-ALS maintains higher absorption capacity after 12 cycles in 100% CO2 flow.