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Cyclic Performance of Waste-Derived SiO2 Stabilized, CaO-Based Sorbents for Fast CO2 Capture


Addition of waste-derived nanosilica significantly enhances the cyclic CO2 uptake and sorption rate of CaO-based sorbents through reuse of photovoltaic waste.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 ∼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.