Extraction and adsorption of U(VI) from aqueous solution using affinity ligand-based technologies: an overview

In terms of energy resource recovery and environmental protection, the separation of U(VI) from aqueous solutions is vital. Adsorption and solvent extraction are the most common separation technologies, which are also widely used for uranium recovery or removal from aqueous solution. The linear structure of uranyl ion and its multiple coordination feasibilities offer great opportunities for its extractive and adsorptive separation. This review briefly summarized and analyzed the recent advances in the separation of uranyl ions from aqueous solutions, mainly focusing on the selective extraction and adsorption using affinity ligands-based technology, which is promising method due to the high selectivity, capable of recovering uranium at low concentration and complicate aqueous environment. The affinity ligands for uranyl ions, including organophosphorus, calixarenes, amidoxime, imidazole and other derivatives were introduced. These donor ligands for design of extraction solvents or adsorbents for the separation of uranyl ions were summarized. The further research on the coordination chemistry towards uranyl ions and removal mechanisms would provide vital information for the development of more effective ligands with higher affinity, stability and compatibility in various systems, which is still challenging.