CaO-based sorbent derived from lime mud and bauxite tailings for cyclic CO2 capture

Using aluminum nitrate (AlN) and bauxite tailings (BTs) as different dopants, and lime mud (LM) as calcium source, a series of CaO-based sorbents were prepared for CO2 capture by dry mixing method; then, the carbonation conversions of multiple carbonation/calcination cycles were detected in a thermogravimetric analyzer (TGA). Effects of different dopants, dopant contents, precalcination conditions, and a long series of cycles on CO2 absorption properties were scrutinized, and the phase composition and morphologies were tested by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Durability studies show that the sample doped with AlN remains a higher absorption conversion (30.88%) after 30 carbonation/calcination cycles. In the meantime, the sorbent doped with BTs showed a lower conversion, which is probably resulted from the impurities from waste BTs. However, the sample BT has a better cyclic absorption stability. In addition, the incorporation of BTs, as a kind of solid waste, not only decreases the preparation cost but also is good for environment. The occurrence of Ca12Al14O33 phase is considered to provide a stable framework inhibiting inactivation of CaO, and improve the CO2 adsorption stability.