Phytic acid modified NH2-MIL-101 via Mannich reaction for highly efficient uranium (Ⅵ) extraction from seawater

An essential part of achieving sustainable uranium resource development was the search for a suitable adsorbent capable of efficiently capturing uranium (Ⅵ) from seawater. Here, a modified metal-organic framework (PA-MIL-101) was prepared by phosphorylation of NH2-MIL-101 with phytic acid (PA). PA-MIL-101 exhibited a specific surface area of 252 m2∙g−1 and proved exceptionally adept at extracting uranium (Ⅵ) from seawater. Batch experiments were conducted to examine how environmental conditions such as pH and natural seawater affect the uranium adsorption performance of the materials. The adsorption capacity of PA-MIL-101 exhibited a remarkable performance, showcasing a substantial 41.8% increase compared to NH2-MIL-101 (the adsorption capacity increased to 416.7 mg∙g−1 at pH = 7 in 100 mg∙L−1 U(Ⅵ) solution). Due to the fast adsorption kinetics, PA-MIL-101 achieves a saturation level of 72.1% within the first 5 min. The removal rate was further elevated to 88.48% in the more intricate natural seawater. The reusability of PA-MIL-101 was demonstrated through five recycling cycles. The porous material PA-MIL-101 has abundant P=O and P–OH active sites, which can strongly complex with uranium (Ⅵ). This feature makes PA-MIL-101 perform effective in natural seawater. Therefore, PA-MIL-101 is considered as a promising supersorbent for efficient removal of uranium (Ⅵ).