Templating synthesis of oxime/amidoxime functionalized hollow nanospheres by air bubbles generated from “Ouzo-Like” effect for fast and massive uranium uptake

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.