Hollow self-assembled hybrid framework based on phytic acid for U(VI) capture from highly acidic aqueous media

Efficient removing uranium (U(VI)) from highly acidic environment remain a great challenge for the adsorbent. Herein, a novel hollow phytic acid-based hybrid material (P(Cr)E-7) was synthesized by a mild facile one-pot self-assembly method without template choosing Cr3+, phytic acid (PA) and ethylenediamine (EDA) as the inorganic and two organic building blocks. P(Cr)E-7 was employed for U(VI) capture in highly acidic wastewater. Thanks to the flexible segment assembled from EDA and PA, and the strong affinity of PA to U(VI), the maximum adsorption capacity of P(Cr)E-7 for U(VI) reached 282.8 mg/g under the condition of pH = 1.0 in static adsorption experiment. Simultaneously, P(Cr)E-7 showed the selectivity efficiency of almost 100 % for An-Ln and pH-dependent selectivity efficiency of 60 % for U(VI) in multi-ions solution with pH = 1.0. Moreover, P(Cr)E-7 showed excellent stability in 0.1 M HNO3 and reusability after three cycles at pH = 1.0 benefiting from stable segment from coordination of Cr(III) and PA. Additionally, the SEM, XRD, FTIR, and XPS analysis revealed the adsorption mechanism that U(VI) exchanges with positively charged EDA+/EDA2+in P(Cr)E-7 to obtain preferred coordination geometry and ligand environment and further coordinates with P-OH/P = O in PA. This study addresses the practical application of effective adsorption of uranium in highly acidic nuclear industrial wastewater and illustrated a novel material design strategy of adsorbents for uranium extraction.