A novel ion-imprinted amidoxime-functionalized UHMWPE fiber based on radiation-induced crosslinking for selective adsorption of uranium

A novel uranium-imprinted adsorbent (AO-Imp fiber) was prepared by radiation-induced crosslinking of amidoxime-functionalized ultra-high molecular weight polyethylene fiber (AO fiber). The porous structure was characterized by scanning electron microscopy (SEM) and positron annihilation lifetime (PAL) spectroscopy after ion imprinting. This ion-imprinted fiber exhibited enhanced adsorption selectivity for uranium in the form of both UO2 2- and [UO2(CO3)3]4- in batch experiments. Compared with AO fiber, the adsorption capacity of the AO-Imp(250) fiber for uranium increased from 0.36 mg g-1 to 1.00 mg g-1 in simulated seawater and from 5.02 mg g-1 to 12.03 mg g-1 in simulated acid effluent, while its adsorption capacities for other co-existing metal ions were particularly low. This study provides an approach to prepare ion-imprinted adsorbents without introducing crosslinking reagents, which may be a promising method for uranium extraction.

Highly Efficient Removal of Thorium in Strong HNO3 Media Using a Novel Polymer Adsorbent Bearing a Phosphonic Acid Ligand: A Combined Experimental and Density Functional Theory Study

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.