Refractory dopant-incorporated CaO from waste eggshell as sustainable sorbent for CO2 capture: Experimental and kinetic studies

• Dopant-stabilized CaO-based sorbents were prepared from waste eggshell for CO2 capture.
• Ti, Cu, Al and Zr were incorporated within the CaO matrix to obtain robust sorbents.
• Zr-doped CaO showed superior performance with conversion of 88% in 20 cycles.
• Chemical reaction and product layer diffusion contributed to the rate controlling step.
• Intrinsic and diffusional activation energies were calculated as 39.4 and 46.5 kJ/mol.

This work investigates the development of dopant-stabilized CaO-based sorbents for CO2 capture and studies the kinetics of the carbonation reaction. Eggshell as biogenesis calcium waste was calcined to obtain low cost CaO powder. Several refractory dopants (Ti, Al, Cu and Zi) were then incorporated within the CaO matrix to prepare robust sorbents. The CO2 capture performance of the developed sorbents was assessed in some calcination–carbonation cycles performed in Thermogravimetric analyzer (TGA). Among the developed sorbents, Zr-doped CaO exhibited superior performance and durability, where a conversion of around 88% could be sustained within 20 cycles. To have an insight into the rate controlling mechanism and fundamental concept of activation energy, kinetic study was performed on the carbonation reaction of the Zr-doped CaO sorbent. Kinetic results based on the shrinking core model suggested that the carbonation mechanism was controlled by a combination of resistances arising from diffusion of CO2 through the carbonate layer and its chemical reaction at the CaO–CaCO3 interface. The intrinsic and diffusional activation energies were obtained as 39.4 and 46.5 kJ/mol, respectively.

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