Preparation and characterization of Melamine-Formaldehyde (MF)-bound cyclen derivatives for efficient removal of uranium [U(VI)] ions from wastewater

Many studies have shown successful functionalization of a polymeric matrix with different chelating moieties for metal ion removal. Melamine-Formaldehyde (MF) resin is a highly porous and robust matrix. It has appropriate chemical and physical properties to serve as a basis for an adsorbent suitable for hazardous material removal e.g., uranium. In this work, we report the synthesis and characterization of new cyclen ligands AspDOTA, GlyDOTA and PropDOTA, which are derivatives of DOTA, a well-known chelating ligand for actinide ions, and the subsequent synthesis of cyclen ligands functionalized MF resins. All new compounds were characterized (¹H and ¹³C NMR for the ligands, MAS solid state ¹³C NMR for the final functionalized polymer). This study demonstrates that U(VI) extraction efficiency of the new MF-cyclen resins depends on the nature of the ligand attached to the polymeric skeleton. It is clear that the MF-AspDOTA resin is the most efficient resin for U(VI) extraction in aqueous solution at pH = 5. Therefore, it is recommended to further investigate the MF-AspDOTA system for wastewater treatment.