Abstract
With the increasing demand of nuclear power plant, the depleted uranium is inevitably emitted and causes environmental risk, hence it is crucial to develop new methods to efficiently eliminate uranium compounds from water. In this work, a bifunctional material core-shell-shell layered double hydroxide (LDH) decorated hollow magnetic polydopamine (MP) microspheres (defined as MPL) were synthesized and evaluated for the cleanup of uranium (VI) from aqueous solutions through specific adsorption. The experimental results showed that the adsorption was significantly affected by pH value rather than ionic strength, reflecting that the interaction was mainly governed by inner-sphere surface complexation owing to the multiple functional groups including imine, catechol, amine, and hydroxyl groups. The adsorption kinetics can be perfectly depicted by the pseudo-second-order model with high uptake percentage of 94.8%, which was superior to the previously reported materials. Interestingly, the maximum adsorption performance can be tuned by changing the thickness of polydopamine shell and the content of LDH, in the order of MP2L2 (344 mg/g) > MP2L3 (291 mg/g) > MP3L2 (245 mg/g) > MP2L1 (211 mg/g) > ML2 (142 mg/g) > MP1L2 (141 mg/g) > MP2 (71 mg/g) > Fe3O4 (34 mg/g) at 298.15 K and pH 5.0. The adsorption mechanism has been thoroughly investigated with techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), thermo-gravimetric analyses (TGA), Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). In summary, the bifunctional material could be applied as promising building block for the enrichment and recovery of uranium (VI) from aqueous solutions in environmental pollution cleanup.
A novel bifunctional material (MP2L2) synthesized by a facile and green method was applied for removal of U(VI). [Display omitted]
•A novel bi-functional layered double hydroxide (LDH) decorated hollow magnetic polydopamine (MP) microspheres were synthesized.•The as-prepared functional materials can be applied for efficient remove U(VI) from aqueous solutions, with high uptake percentage of 94.8%.•The adsorption of U(VI) and interaction were mainly governed by inner-sphere surface complexation owing to the multiple functional groups.•Adsorption kinetics can be perfectly simulated by the pseudo-second-order model, the maximum adsorption performance can be tuned.