Regulation of chain conformation and synergistic effect of auxiliary groups towards polyamidoxime for highly efficient uranium extraction from seawater

Amidoxime-based polymers have been widely regarded as ideal adsorbents for uranium extraction from seawater. However, significant challenges remain in the efficient utilization of amidoxime groups on the polymers which is closely related to the conformation of molecular chains in complex marine environments. Herein, by integrating multi-scale computational simulation with chain conformation regulation, three representative auxiliary group were designedly introduced to polyamidoxime (PAO) by grafting glycine, aminomethylsulfonic acid and aminomethylphosphonic acid. Firstly, the hydrophilicity of adsorbents was directly observed to increase significantly after modification by contact angle test and swelling test. Furthermore, the chain conformation was investigated by combined SAXS and MD simulation under real factors from seawater. Finally, uranium adsorption performance and mechanism were investigated by XPS and DFT calculation. The minimum contact angle reaches 26.9 degrees and the maximum swelling rate is above 153.4 %. The conformation of the modified PAO was much more stretched than the raw one, with a radius of gyration up to 161.5 nm for PAO-AMP. The uranium adsorption capacity of PAO was only 165.5 mg/g, while that of the modified adsorbents PAO-AMP went up to 375.0 mg/g. The above results indicate that auxiliary groups played a role not only in optimizing the chain conformation of adsorbents but also in enhancing coordination capacity with uranium, which is beneficial for uranium extraction from seawater. This study offers a new point of view to assess adsorption phenomena of polymers, bridging chain conformations in different environment at the mesoscopic level with metal-ligand interactions at the molecular level.