Spatially isolated magnetic-mesoporous units in one anisotropic Janus nanoparticle for rapid and selective extraction of uranium

Iron oxide with superparamagnetic property and mesoporous silica with large surface areas are both important to design multifunctional sorbents, and magnetic-mesoporous nanoparticles of asymmetric morphology may make full use of their advantages. To address this, spatially isolated magnetic-mesoporous units in one anisotropic Janus nanoparticle with abundant amidoxime (AO) groups (AO-Fe 3 O 4 @C&mSiO 2 ) was synthesized for rapid and selective extraction of uranium. Chemically and structurally anisotropic AO-Fe 3 O 4 @C&mSiO 2 was composed of one AO functionalized mesoporous silica nanorods and a carbon coated Fe 3 O 4 nanoparticle, which displayed excellent surface area (139.9 m 2 g −1 ) and saturation magnetization (28.79 emu g −1 ). Thus, AO-Fe 3 O 4 @C&mSiO 2 showed fast adsorption kinetics for reaching adsorption equilibrium within 30 min, and then they were able to be collected in 3.0 s under an external magnetic field. The maximum and spontaneous adsorption capacity for uranyl ions was obtained by fitting thermodynamic data through Langmuir model at 298 K was 62.12 mg g −1 , and AO-Fe 3 O 4 @C&mSiO 2 achieved the highest uptake amount and removal rate of almost 100% towards uranium in the presence of competitive ions. Meanwhile, the results from ten regeneration cycles confirmed the high service lifetime of AO-Fe 3 O 4 @C&mSiO 2 . This work not only demonstrates a strategy for preparing multifunctional sorbents with anisotropic structure but also provides a method for selective uranium extraction.