Cyclic performance of waste-derived SiO2 stabilized, CaO-based sorbents for fast CO2 capture

Calcium-looping technology has been identified as one of the most favorable CO₂ capture techniques for the implementation of carbon capture, utilization, and storage (CCUS); however, the rapid deactivation of CaO sorbents due to sintering is currently a major barrier of this technology. We report for the first time an environmentally benign and cost-effective strategy to reduce sintering by adding waste-derived nanosilica, synthesized from photovoltaic waste (SiCl₄), into Cao-based sorbents through a simple dry mixing procedure. The as-synthesized sorbent (90% CaCO₃-W) resulted in final CO₂ uptake of 0.32 g(CO₂) g(CaO)^-1 within 5 min of carbonation. Even under the most severe calcination conditions (at 920 °C in pure CO₂), it still maintained a stable capture capacity, with CO2 uptake of 0.23 g(CO₂) g(CaO)^-1 after 30 cycles. Additionally, the CO₂ uptake percentage reached similar to 90% in the fast carbonation stage (~20 s), which is of great significance for real applications. The most likely stabilization mechanism was considered on the basis of N₂ physisorption isotherms and X-ray diffraction patterns. It was concluded that stable and refractory larnite (Ca₂SiO₄) particles were formed during 2-h thermal pretreatment at 900 °C, leading to sintering resistance. This strategy significantly enhanced the cyclic stability and carbonation rate of CaO-based sorbents through the reuse of SiCl₄ and is thus a green technology for scaled-up fast CO₂ capture.