Synthesis of Amidoxime Functionalized Core-Shell Magnetic Composites for the Highly Efficient Removal of Uranium from Simulated and Real Wastewater

Abstract

The employment of magnetic nanomaterials to treat uranium-containing wastewater is highly desirable but maintains an enormous challenge. To overcome the challenge, herein, a series of amidoxime functionalized core-shell adsorbents AO-Fe3O4/P (MBA-AN) with magnetically separation character were developed by introducing high concentration of amidoxime to Fe3O4/P (MBA-AN) prepared via distill-precipitation polymerization of N, N'-methylene diacrylamide (MBA) with acrylonitrile (AN). By optimizing the polymerization system, abundant amidoxime ligands which served as sorption sites to supply the strong affinity for uranium could be ushered onto the sorbent. Thus, the maximum sorption capacity (qmax) of AO-Fe3O4/P (MBA-AN) at pH of 4.5 can run to 429.5 mg g-1, which outperformed most reported magnetic materials. The as-constructed core-shell structure could enhance the sterling acid resistibility, and the morphology, chemical structure and adsorption performance nearly maintained immutable even after immersed at pH 1.0 for 12 h. Due to its superparamagnetic character, the composite could also be magnetically reclaimed within 20 s, and be used repeatedly for leastways six times without palpable loss of sorption amount. The satisfactory uranium removal was principally ascribed to the interaction of uranium with amino and hydroxyl of amidoxime ligand, evidenced by XPS and DFT method. The DFT outcome revealed the geometric structure of 1:1 of UO22+ with amidoxime group could depict the binding model of uranium and the sorbent well. More importantly, in real wastewater containing uranium, the uranium removal efficiency obtained by the sorbent could reach up to 99.0 %, and the separation factor (SU/M) value regarding all competing cations surpassed 658.1, resulting in the concentration of treated wastewater meet discharge standards set by World Health Organization (WHO). This work brings a prospective hereafter for magnetic nanomaterials in the disposal of real uranium-containing wastewater.

Keywords: Magnetic composite, Uranium capture, Amidoxime, Distillation-precipitation polymerization, core-shell structure