1. Conclusions Ca-Al bimetallic oxides enriched with C 3 A and C 12 A 7 were successfully synthesized by CaO and alumina at Ca/Al ratio of 2 and 1 by a solid-state sintering method for Clremoval from saline wastewater. Ca-Al-based sorbents prepared by ?-Al 2 O 3 obtained much higher Cl -removal efficiency than those prepared by Al 2 O 3 . Higher calcination temperature improved the crystallinity of bimetallic oxides. C 3 A and C 12 A 7 -rich sorbents prepared at 1200 and 1100 �C achieved the highest Cl -removal of 83.3% and 73.1%, and the former had a higher AUR of 45.2%. XRD and XPS analyses revealed that sorbents synthesized using ?-Al 2 O 3 had higher atomic density, higher ratio of absorbed oxygen to lattice oxygen, and higher 4 Al/ 6 Al ratio than that using Al 2 O 3 , resulting in enhanced reactivity and superior Cl -removal performance. The sorption isotherms and thermodynamic studies confirmed that the sorption of Cl -on Ca-Al oxides was spontaneous and exothermic, and ?-CA-2-1200 exhibited a maximum sorption capacity of 243.7 mg/g. The removal mechanism of Cl -by Ca-Al oxides involved the hydration-induced mineral phase transformation and structural reconstruction, leading to the formation of AFm-Cl phases accompanied by surface electrostatic attraction. The intense competition between Cl -and OH -during the hydration of C 12 A 7 -rich sorbent produces more complex products;Methodology
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