Modulation of calcination conditions on the defluorination performance of nano Ce-based adsorbents: The key roles of Ce valence state and oxygen vacancy

Excessive fluoride (F − ) in water environment is a widespread concern, and economical and efficient adsorption is widely used defluorination technology. In this study, a series of cerium-based adsorbents (Ce@C) with different structural properties were synthetized by adjusting the calcination conditions to explore their effect on the F − adsorption capacity of Ce@C and intrinsic mechanism. Results indicated that the best performing Ce@C had the maximum adsorption capacity (340.71 mg/g) and a wide pH working range (2–12). The adsorption process of F − conformed to the pseudo-second-order model and the Temkin model, proving that F − adsorption onto Ce@C was mainly dominated by chemisorption. Different calcination conditions altered the content of Ce(III) and oxygen vacancies in Ce@C, and their contents exhibited a significant effect on the F − adsorption performance of Ce@C, which showed a strong positive correlation (R 2  = 0.982 and 0.933). Density functional theory (DFT) calculations further proved that the presence of Ce(III) and oxygen vacancies could provide richer coordination numbers to promote the complexation of F − and Ce@C. This work re-reveals the F − adsorption behavior and intrinsic mechanism onto cerium-based adsorbents, and also provides a theoretical basis for the subsequent design of cerium-based adsorbent materials for defluorination.