Investigation of CaO-based sorbents derived from eggshells and red mud for CO^sub 2^ capture

A series of CaO-based sorbents, using low-cost eggshells and red mud (Rm) pretreated by the acid leaching process as raw materials, were synthesized by the dry mixing method. The effects of different sodium leaching ratios, Rm doping contents, and eggshells as calcium precursors on CO2 capture properties of the CaO-based sorbents are discussed in this paper. The cyclic carbonation/calcination performance of the as-prepared sorbents was evaluated by a thermogravimetric analyzer. The phase compositions and morphologies of the sorbents were characterized by XRD and SEM, respectively. The as-prepared sorbents doped with 10 wt% Rm3 (with a sodium leaching ratio of 99.91%) showed a superior cyclic conversion of 46.67% after 100 carbonation/calcination cycles. The existence of the Ca12Al14O33 phase was probably responsible for the excellent CO2 cyclic performance.