Development of robust CaO-based sorbents from blast furnace slag for calcium looping CO2 capture

CaO-based calcium looping materials have received great interest for their use in thermochemical CO2 capture and energy storage, as well as CO2-related energy conversion processes. In this paper, the development of robust CaO-based CO2 sorbents using waste blast furnace slag (BFS) as a sustainable and environmentally benign feedstock is reported. Calcium and magnesium in the BFS can be facilely acquired through an acid extraction process, and appear in the form of CaO and MgO, which serve as a CO2 carrier and structural stabiliser, respectively, in the prepared CO2 sorbents. The BFS-derived sorbent prepared in this study exhibited a superior CO2 capture capacity of 0.37 g(co2)/g(sorbent) with an average cyclic deactivation rate as low as 2.3%, representing a balanced performance between CO2 uptake and cyclic stability as compared to most other waste-derived, CaO-based CO2 sorbents. This study demonstrated that CaO-stabiliser interaction largely determines the CO2 capture performance of CaO-based sorbents, and the Ca/Si ratio in the BFS-derived sorbent should be effectively controlled to allow the material to capture CO2 at a high performance.