Selective fluoride removal from wastewater with unsaturated aluminum/carbon-encapsulated core-shell adsorbent: Performance, mechanism and application.

Selective adsorption of fluoride (F-) is an efficient and feasible technology for the remediation of F- contamination in wastewater. However, there are scientific difficulties unsolved regarding low adsorption capacity and selectivity, restricting its extensive engineering applications, especially in industrial wastewater. In this work, selective F- removal from wastewater was achieved through functional groups interaction and ligand with a core-shell structure material (aAlOx@C). This material offered higher adsorption capacity (26.77 mg/g) and superior performance for F- removal (95.73%) under initial concentration of 9.5 mg/L. Both groups interaction and ligand (C-F and Al-F bond) were contributed to the higher adsorption capacity and selectivity for F-. Density functional theory showed that the decrease of overlapping energy bands between Al 3p and F 2p and the increase of ΔE (1.72 eV) between C-F and Al-F facilitated the conversion of C-F into Al-F bond. The constructed unsaturated Al not only promoted the group exchange between -OH and F-, but also served as a host for selective F- removal via Al-F bond. Impressively, such material established excellent adsorption capacity (16.24∼24.19 mg/g) for different industrial wastewater treatment with discharge standard (3 mg/L) in continuous-flow mode.