N-benzoyl-n-phenylhydroxylamine impregnated Amberlite XAD-4 beads for selective removal of thorium

Selective Capture Mechanism of Radioactive Thorium from Highly Acidic Solution by a Layered Metal Sulfide

Thorium as a potential nuclear fuel for the next-generation thorium-based molten salt reactors holds significant environmental and economic promise over the current uranium-based nuclear reactors. However, because thorium (Th⁴⁺) usually coexists with other rare earth elements, alkali or alkaline earth metals in minerals, or highly acidic radioactive waste, seeking acid-resistant sorbents with excellent selectivity, high capacity, and fast removal rate for Th⁴⁺ is still a challenging task. In this work, we investigated a robust layered metal sulfide (KInSn₂S₆, KMS-5) for Th⁴⁺ removal from strong acidic solutions. We report that KMS-5 could capture Th⁴⁺ from a 0.1 M HNO₃ solution with extremely high efficiency (∼99.9%), fast sorption kinetics (equilibrium time < 10 min), and large distribution coefficient (up to 1.5 × 10⁶ mL/g). Furthermore, KMS-5 exhibited excellent sorption selectivity towards Th⁴⁺ in the presence of large amounts of competitive metal ions like Eu³⁺, Na⁺, and Ca²⁺. This extraordinary capture property for Th⁴⁺ is attributed to the facile ion exchange of Th⁴⁺ with K⁺ in the interlayers and subsequent formation of a stable coordination complex via Th-S bonds. These results indicate that KMS-5 is a promising functional sorbent for the effective capture of Th⁴⁺ from highly acidic solutions.

Solvent impregnated resins for the treatment of aqueous solutions containing different compounds: a review

In this review paper, a complete study and analysis of the research articles dealing with the removal of various organic and inorganic pollutants using solvent impregnated resins (SIR) is carried out. The method of impregnation, characterizations of prepared resin, and regeneration techniques of different SIRs for batch and continuous fixed bed columns are presented. The effects of different operating parameters (e.g., loading of solvent on the resin, dosage of adsorbent, initial solute concentration, pH, temperature, time, ionic strength) on the separation efficiency of SIR in the batch mode are discussed. Thermodynamic parameters (change in Gibbs free energy, enthalpy, and entropy) are tabulated from the data available in the literature, and if not given, then their values are calculated and presented. The influence of parameters (flow rate, bed height, pH, concentration of the solution, etc.) on the fixed bed column performance is analyzed. Design aspects of the column are also discussed, and the dimensions of fixed bed columns for industrial applications are proposed.

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.