Multi-promoters modified CaO-based sorbent derived from mixed waste slag for long-term CO2 cyclic capture

Calcium looping, a carbon dioxide (CO 2 ) capture technique, may provide an effective route to eliminate climate change brought by the steadily rising anthropogenic CO 2 emissions. However, the key challenge for calcium looping is the sintering-induced decay over the numerous cycles for CaO-based sorbents. Herein, multi-promoters modified CaO-based sorbents, derived from the mixed waste slag of marble waste powder (MWP) and rare earth polishing powder wet slag (REPP), are prepared by a simultaneous hydrating and calcining process. The cyclic CO 2 capture is explored by a thermogravimetric analyzer, and the promotion mechanism is investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, CO 2 temperature-programmed desorption, and reaction kinetics fitting. Results indicate that the multicomponent promoters from the REPP, including CeO 2 , Ca 12 Al 14 O 33, and LaPO 4 , enhance the carbonation cyclic activity of CaO from MWP. The best-performing MWP-REPP sorbent with 15 wt% REPP shows less than a 10 % drop decay and the CO 2 carbonation conversion remains at 75 % (0.46 g CO 2 /g sorbent) after 50 repeated cycles. The excellent cyclic capture performance is attributed to the synergistic interaction between the promoters and CaO, where the CeO 2 promoter owns abundant oxygen vacancies, and the Ca 12 Al 14 O 33 and LaPO 4 promoters provide the blocked effect, thus facilitating the CO 2 sorption and inhibiting the CaO from sintering. This work presents useful guidance for improving the cyclic sorption stability of CO 2 from waste slags.