High efficient removal of U(VI) by covalent organic frameworks fabricated by mechanochemical method: Adsorption process, mechanism and surface complexation modeling

Herein, covalent organic frameworks (i.e., TpBD) were fabricated by mechanical delamination of 1, 3, 5-triformylphloroglucinol (Tp) and benzidine (BD) using NaHCO3 as foaming agent. The batch characterizations revealed that flower-like TpBD nanosheets exhibited the large porosity, high BET specific area (139 m2/g), small pore size (∼ 14 Å), remarkable stability and keto form. The adsorption process of U(VI) removal by TpBD displayed the fast sorption rate (equilibrium within 0.5 h), high adsorption capacity (167 mg/g) and good re-usability (no significant difference after five cycles). According to analysis of X-ray photoelectron spectroscopy (XPS) and surface complexation modeling, the removal mechanism of U(VI) by TpBD was chemisorption and inner-sphere surface complexation. These findings are of great importance for the application of covalent organic frameworks fabricated with rapid and easy-to-operate mechanochemical method in actual environmental cleanup. [Display omitted] •Covalent organic frameworks (TpBD) were fabricated by mechanochemical delamination.•TpBD had high U(VI) sorption capacity, fast adsorption rate and good reusability.•Sorption mechanisms of U(VI) on TpBD were chemisorption and surface complexation.•TpBD is a promising candidate for U(VI) removal in actual environmental cleanup.