Abstract

Simple and green synthesis of oxime or amidoxime functionalized hollow sorbents are critical for meeting the demands of highly efficient uranium extraction. To address this, a facile methodology using air bubbles generated from the “Ouzo-Like” effect as templates to synthesize oxime/amidoxime functionalized hollow PDA nanospheres (H-PDA-SO and H-PDA-AO) with fast and massive uranium extraction performances was reported. When 50 mL of Tris solution (0.6 mg mL−1) was mixed with n-propanol (6.25 mL) for 2.0 min, nanobubbles with the mean size of 56.7 nm spilled out, and uniformly sized H-PDA-SO nanospheres with oxime groups (about 250 nm) and H-PDA-AO nanospheres with amidoxime groups (about 150 nm) were simply obtained via self-assembled polydopamine and post-modification around the air/water interface. Owing to the accessible affinity sites and hollow structure, H-PDA-SO and H-PDA-AO displayed high maximum adsorption capacities (103.09 mg g−1 and 331.62 mg g−1 at 298 K) and fast adsorption rate (below 60 min) with high removal efficiency. Under the influence of coexisting ions, H-PDA-SO and H-PDA-AO showed not only a high uranium adsorption capacity but also a more predominant capacity than all the competing ions. Moreover, H-PDA-SO and H-PDA-AO exhibited high stability as well as excellent recyclability toward uranium capture after five regeneration cycles. Surface coordination of oxime/amidoxime sites with uranium was the main binding mechanism, and negative charged O-containing function groups enhance this affinity interactions.

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