Promotional effect of NaNO3/NaNO2 on CO2 adsorption performance of MgO sorbents

The magnesium oxide (MgO) sorbents doped with different NaNO 3 /NaNO 2 molar ratios were prepared to improve their stability over multiple cycles. Regulating the NaNO 3 /NaNO 2 molar ratio effectively improved the CO 2 adsorption performance of the sorbent. The MgO sorbent with the NaNO 3 /NaNO 2 molar ratio of 0.8 exhibited outstanding performance and stability. Characterization and density functional theory calculations confirmed the positive effects of the appropriate NaNO 3 amount in improving the adsorption activity, whereas the suitable NaNO 2 amount slowed the sintering step and improved stability. Notably, the molten salt remained stable during cycling and did not decompose even at high regeneration temperatures, guaranteeing the cyclic stability of the sorbent. Further characterization showed that the CO 2 sorption drop in the first few cycles was ascribed to the decline in the active surface owing to the aggregation of MgO particles, incomplete regeneration of sorbents, and segregation of molten salt on the sorbent surface.