Functionalized Covalent Organic Frameworks for Rapid and Selective Extraction of Uranium from Wastewater Through Experimental and Theoretical Studies

Abstract

Selective extraction of uranium from aqueous solutions is crucial for the remediation of radioactive contamination and the recovery of uranium from seawater. Herein, carboxyl (-COOH) groups were introduced during the preparation of LZU-COF (LZU represents Lanzhou University) using the static synthesis method at room temperature. Owing to the excellent structural, thermal stability as well as effective functional groups, the removal capacity of U(VI) by LZU-COF-COOH significantly higher than that of the original LZU-COF. Furthermore, LZU-COF-COOH exhibited impressive reaction kinetics with the removal process reached equilibrium within 1 h, and significant adsorption selectivity for uranium over coexisting metal ions. Spectroscopic analysis and theoretical calculations demonstrated that UO22+ ions were bound to the carbonyl groups through coordination interaction and electrostatic interactions. DFT calculations further demonstrated that the optimized LZU-COF-COOH had smaller bond lengths and bond angles with UO22+, as well as larger binding energies and abundant binding sites, confirming the great potential of LZU-COF-COOH for radionuclide removal. This work paves the way for the rational development of functionalized COFs and highlights their potential in the remediation of radioactive pollution.

Keywords: covalent organic frameworks, uranium, spectroscopic analysis, theoretical calculations