Highly stable CO2 capture performance of binary doped carbide slag synthesized through liquid precipitation method

Calcium-based looping process plays a vital role in post-combustion CO capture, fossil fuel combustion and hydrogen production. Carbide slag (CS) is a typical high-calcium industrial waste with superior CO sorption capacity, which is an ideal calcium precursor. In this study, the highly stable calcium-based CO sorbents were innovatively synthesized via the liquid precipitation of carbide slag and binary doping materials (MgO, NiO and ZrO). The as-synthesized binary doped carbide slag (CS-MgO-ZrO) possessed an average CO uptake of 0.32 g-CO·g-sorbent during 20 cycles. Even under the most severe calcination conditions (at 900 °C in 100 vol% CO), it still maintained a stable capture capacity with a final CO uptake of 0.28 g-CO·g-sorbent after 20 cycles. Specially, the average decay rate of “CS-MgO-ZrO” under the severe calcination condition was merely 0.92% per cycle, highly decreased by 67.75% than carbide slag. The most likely stabilization mechanism of binary doping was studied based on various characterization techniques, which was concluded that MgO could improve the initial CO uptake, while NiO and ZrO could increase the cyclic stability. This strategy significantly enhances the cyclic stability of calcium-based sorbents via binary doping and realizes the high-value reuse of carbide slag, and is thus an effective approach to post-combustion CO capture.