Dynamic Intermediate-Temperature CO₂ Adsorption Performance of K₂CO₃-Promoted Layered Double Hydroxide-Derived Adsorbents

The dynamic adsorption characteristics of K₂CO₃-promoted layered double hydroxides (LDHs)-based adsorbent, with organic and inorganic anion intercalation, were studied. MgAl–LDH, K₂CO₃/MgAl–LDH, and K₂CO₃/MgAl–LDH(C16) with varying K₂CO₃ loads were prepared and used for intermediate-temperature CO₂ sequestration. The adsorbent was thoroughly characterized using X-ray diffraction, Brunauer–Emmett–Teller, scanning electron microscopy, and Fourier Transform Infrared Spectroscopy techniques, which revealed enhanced adsorption properties of MgAl–LDH, due to K₂CO₃ promotion. Thermogravimetric CO₂ adsorption tests on the constructed adsorbent materials showed that the 12.5 wt% K₂CO₃/MgAl–LDH(C16) adsorbent with organic anion intercalation exhibited optimal adsorption activity, achieving an adsorption capacity of 1.12 mmol/g at 100% CO₂ and 350 °C. However, fixed-bed dynamic adsorption tests yielded different results; the 25 wt% K₂CO₃/MgAl–LDH prepared through inorganic anion intercalation exhibited the best adsorption performance in low-concentration CO₂ penetration tests. The recorded penetration time was 93.1 s, accompanied by an adsorption capacity of 0.722 mmol/g. This can be attributed to the faster adsorption kinetics exhibited by the 25 wt% K₂CO₃/MgAl–LDH adsorbent during the early stages of adsorption, thereby facilitating efficient CO₂ capture in low-concentration CO₂ streams. This is a conclusion that differs from previous reports. Earlier reports indicated that LDHs with organic anion intercalation exhibited higher CO₂ adsorption activity in thermogravimetric analyzer tests. However, this study found that for the fixed-bed dynamic adsorption process, K₂CO₃-modified inorganic anion-intercalated LDHs perform better, indicating their greater potential in practical applications.