It is still a great challenge to develop magnetic adsorbents for the highly efficient entrapment of uranium from aqueous solution. Herein, a novel magnetic adsorbent (denoted as Fe 3 O 4 /P (AA-MMA-DVP)) bearing phosphine oxide ligand was designed and synthesized via a DPE (1,1-diphenylethylene) method based on DPE as radical controlling agent, showing an excellent adsorption capacity for uranium at pH 4.5 and outstanding selectivity in aqueous media including 14 coexisting ions. The magnetic adsorbent showed a q max value of 413.2 mg g −1 at 298 K and pH 4.5, which was higher than that of most of other magnetic adsorbents. The outstanding selectivity (S u = 95.8%) for uranium was reasonably ascribed to the strong complexation between UO 22+ and PO groups anchored on the polymer skeletion, which was evidenced by experimental results. Furthermore, the magnetic adsorbent could be isolated by magnetic force and be recycled at least five times without significant loss in adsorption capacity. This work provided a convenient synthetic route to develop a novel magnetic adsorbent with high capacity and strong selectivity for the entrapment of uranium from aqueous solution.

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It is an important task to develop the technologies for the extraction of thorium from strong HNO3 media with high efficiency. In this work, solvothermal polymerization of trimethylolpropane trimethacrylate (TRIM) and vinylphosphonic acid (VPA) has been used to synthesize a novel polymer material P (TRIM-VPA) bearing a phosphonic acid ligand for thorium entrapment in strong HNO3 media. Under the current experiment condition, the polymer adsorbents showed a record-breaking maximum adsorption capacity for thorium (403.2 mg g–1) with an excellent selectivity for thorium over Gd­(III), Nd­(III), Ce­(III), Sr­(III), Sm­(III), and La­(III) in 4 mol L−1 HNO3 media at 298 K. The content of PO ligands existing on P (TRIM-VPA) has an obvious influence on the adsorption capacities for thorium. Increasing the content of PO ligands would result in higher adsorption capacity of thorium. The isothermal data fitted well the Langmuir model, and the sorption kinetics fitted the pseudo-second-order model. The adsorption behavior was not only spontaneous but also endothermic in reality. Both XPS and FTIR studies revealed that the adsorption interaction for thorium extraction was acquired only via the coordination of PO groups anchored on P (TRIM-VPA) with thorium. Moreover, P (TRIM-VPA) still had high adsorption capacity after five sorption–desorption cycles in 4 M HNO3 media. DFT calculation suggested that a 1:2 ratio of Th­(IV) with the PO group on the same graft chain validated the experimental findings. Thus, the solvothermal polymerization method might be a promising way for the synthesis of the adsorbents for the highly efficient extraction of thorium from strong HNO3 media.

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