Facile Preparation of Porous CaMgAl Hydrotalcite-Like Derived Mixed Oxides through Alkaline Etching of KOH for CO2 Capture

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Hydrotalcite-like compounds are effective adsorbents for adsorbing and separating CO2 from flue gas. However, this kind of adsorbents has the problems of poor dispersibility and low available specific surface area. In response to these problems, porous CaMgAl mixed oxides were obtained by KOH alkaline etching of CaMgAl hydrotalcite-like hydroxides prepared by one-pot hydrothermal method. The characterization results demonstrated that after alkaline etching, the Al species were partly removed and some mesopores were formed, along with the increase of the specific surface area. Correspondingly, the CO2 uptake of the alkaline-etched adsorbent was up to 380.7 mg/g, ascribed to the developed pore structure. The porous structure facilitated the exposure of alkaline adsorption active sites and made it easier to combine CO2 molecules with adsorption sites on the adsorbent surface. Besides, the alkaline-etched adsorbent had a good cyclic stability after 10 cycles with maintaining 78% of the initial CO2 uptake, which was potentially applied for CO2 capture.