Development of CaO-based sorbent doped with mineral rejects-bauxite-tailings in cyclic CO2 capture

A highly efficient CaO-based sorbent, using inexpensive materials (CaCO3) and mineral rejects (bauxite-tailings) as reactants, was tested for carbonation conversions for 15 carbonation/calcination cycles in a thermogravimetric analyzer (TGA). The morphology was investigated by scanning electron microscopy (SEM) and the phase composition was determined by X-ray diffraction (XRD). Effects of different bauxite-tailings (BTs)/CaO ratios and thermal pretreatment temperatures on carbonation conversion were investigated in this study. The sorbent doped with 5% BTs (calcined at 900 °C for 3 h) showed superior cyclic stability during 50 carbonation/calcination cycles (being >42% conversions after 50 cycles). Mayenite (Ca12Al14O33) in the CaO-based sorbents doped with BTs is responsible for the favorable performance. It can provide a stable framework inhibiting sintering over multiple cycles. In addition, this study may offer the possibility of recycling the BTs from aluminum manufacture.