Self-locomotive composites based on asymmetric micromotors and covalently attached nanosorbents for selective uranium recovery

Nanosized sorbents are widely used for uranium (VI) recovery due to their high specific surface area, but the research on the integration of micromotors with nanosorbents to establish self-locomotive composites is still worth exploring. Thus, self-locomotive composites PS@PDA@Ag/SiO 2 -AO (PPA/SA) based on asymmetric micromotors and covalently attached nanosorbents were designed for selective uranium recovery. Pickering emulsion, as an important micro-reactor, was firstly adopted to prepare Janus microspheres with chemically distinct structure (PS@PDA@Ag), on which one hemisphere was loaded with catalytic silver (Ag) nanoparticles. Then, amidoxime (AO) decorated SiO 2 nanospheres were covalently attached onto another hemisphere of PS@PDA@Ag, anisotropic configuration of as-prepared PPA/SA avoided the overlap of catalytic and binding sites. The self-propelled motion of PPA/SA induced by asymmetrical bubble evolution by H 2 O 2 was observed, and the maximum speed was about 25 μm s −1 in case of 5 % H 2 O 2 . The uranium adsorption onto PPA/SA achieved 92 % of the equilibrium amount (29.31 mg g −1 ) in the first 20 min, and this value increased to 38.71 mg g −1 under the condition of H 2 O 2 , suggesting that autonomous movement achieves rapid mixing and mass transportation. The maximum adsorption amount ( Q m ) is 114.0 mg g −1 at 298 K according to the Langmuir model. In addition, PPA/SA exhibited remarkable selectivity for uranium even in the presence of large amounts of Na + , Mg 2+ , K 2+ , Ca 2+ and other ions in the simulated seawater solution.