Preparation of molten salt promoted MgO for efficient CO2 capture by microwave method: Performance evaluation and mechanism exploration

MgO’s great potential for capturing CO 2 has drawn a lot of attention, but the limited O 2– sites prevents its further development. This work proposed a microwave-induced method (microwave hydrothermal and microwave sintering) to produce high-performance MgO CO 2 adsorbent and was further modified using carbonates (K 2 CO 3 ) and nitrates of alkali metals (NaNO 3 , KNO 3 ). The outcomes demonstrated that the small particle size MgO nanocrystals (6.20 nm) with a CO 2 uptake of 1.8 mmol·g −1 could be produced by a unique method of microwave heating from the inside out. Among the modified samples, addition of 20 mol% NaNO 3 on the surface of MgO exhibited the highest CO 2 uptake (11.91 mmol·g −1 ), and the uptake was still 7.9 mmol·g −1 after 10 cycles. The addition of molten salt changed the adsorbent’s active sites, resulting in an increase in O 2– alkaline sites and the activation of MgO lattice defects, both of which improved the sample’s CO 2 adsorption performance. This work could offer a new idea for creating affordable and effective CO 2 solid adsorbents to capture CO 2 .