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Ion-absorbed rare earth ores radioactive residues (IREORR) are a class of waste residue from the production of rare earth elements (REEs). Because of its radioactive dose, IREORR are usually stored in waste warehouses. IREORR are difficult to be disposed of. However, it contains relatively high concentrations of REEs, which can be considered as a valuable secondary resource. In this paper, a novel process is developed for the separation of thorium (Th) and recovery of REEs from IREORR hydrochloric acid leachate with primary amine N1923 and Cyanex® 572, respectively. The effects of sulfate concentration, extractant concentration and pH on N1923 extraction in hydrochloric acid solution were investigated in detail. The results show that the extraction capacity of N1923 can be improved by adding sulfate to the solution and increasing the concentration of N1923. Acidity has little effect on the extraction of Th when pH is higher than 1. As for the stripping, REEs are more easily stripped from loaded organic phase than Th, and nitric acid is a better stripping agent than hydrochloric acid. Combined with the extraction of Cyanex® 572 for REEs, a fractional extraction experiment for separating Th and enriching of REEs was performed. The yield of Th is higher than 99.9% and the concentration of REEs is enriched to 183.84 g/L.

In this paper, a series of high performance near-infrared reflective pigments based on Bi3YO6 doped with Fe2O3 and Tb4O7 were prepared by high-temperature calcination method. The pigments were characterized by some analytic techniques, such as XRD, Particle size analyzer, SEM, EDS, UV–vis–NIR spectrophotometer, CIE L*a*b* (1976) color space and infrared thermal imaging. Experimental results showed that the Fe2O3 doping in Bi3YO6 could change the color from bright yellow to ochre red. The substitution of Tb (IV)-doped pigments changed the color to dark orange. The doping of Fe (III) and Tb (IV) contributed to enriching the color diversities of pigments. Among the synthesized pigments, Bi3-xFexYO6 and Bi3Y1-xTbxO6+δ displayed a disordered defective fluorite-type structure. The effect of doping Fe (III) and Tb (IV) reduced the near-infrared reflectance of the pigment. Excepting for Bi3-xFexYO6 (x = 0.8), the near infrared reflectance of some other pigments were higher than the China National standard (CNs). Chemical resistance tests showed that the pigments had excellent acid and alkali resistance. Finally, the application practical of traditional iron oxide yellow pigment and three prepared pigments, i.e., Bi3YO6, Bi3-xFexYO6 (x = 0.4) and Bi3Y1-xTbxO6+δ (x = 0.05) were studied and compared by infrared thermal imaging. The test results showed that Bi3YO6 still had a strong near-infrared reflection effect after being painted. Compared with traditional iron yellow pigment, Bi3YO6 could reduce the surface temperature of galvanized sheet by 20 °C under the illumination of infrared light. The series of Fe (III) and Tb (IV) doped pigments prepared in this paper have revealed some promising application values.

Herein we report a new 4-fold interpenetrated metal–organic framework (MOF) functionalized with O− groups for selective Th(IV) capture, the activated samples 1a exhibited a high adsorption capacity for pure Th(IV) ions (Kd = 3.16 × 105 mL g−1) and the amount of metal ions adsorbed on the adsorbent was 165.61 mg g−1. A high removal efficiency of 99.75% was achieved within 10 min with an initial Th(IV) concentration of 100 mg L−1 and the adsorption data followed the pseudo-second-order model. In addition, the separation coefficient (S) of Th(IV) to metal ions with different valence states such as Th(IV)/La(III), Th(IV)/Sm(III), Th(IV)/Ho(III), Th(IV)/Cd(II) and Th(IV)/K(I) achieved values of 19.66, 26.83, 16.90, 11.26 and 255.79, respectively. Even given the fact that MOFs with O− groups showed high affinity for Pb(II) ions, our adsorption studies for compound 1a revealed a separation coefficient (STh(IV)/Pb(II)) of 4.36. Further, the adsorption of Th(IV) ions to compound 1a was investigated by FT-IR, SEM-EDS and XPS.

An uncoordinated salen-containing metal-organic framework (MOF) obtained through postsynthesis removal of Mn(III) ions from a metallosalen-containing MOF material has been used for selective separation of Th(IV) ion from Ln(III) ions in methanol solutions for the first time. This material exhibited an adsorption capacity of 46.345 mg of Th/g. The separation factors (β) of Th(IV)/La(III), Th(IV)/Eu(III), and Th(IV)/Lu(III) were 10.7, 16.4, and 10.3, respectively.

In this article, a new family of rare earth (RE) complexes with formula of [RE2(EPOA)6(H2O)3]·H2O, where RE = La, Nd, Er, Y and the HEPOA = 4-ethyl phenoxyacetic acid was synthesized. Their structures were characterized by single-crystal X-ray diffraction, FT-IR, and elemental analysis. The four complexes are isostructural and consist of two-dimensional networks. The decrease in Ln–O bond lengths reflects the lanthanide contraction. The structures of HEPOA ligand, the resulting dimer formed by hydrogen bond and their hydrogen binding energy were studied by density functional theory (DFT). In addition, atoms in molecules (AIMs) analysis revealed the presence of partial closed shell interactions between REs and oxygen atoms of HEPOA ligand in the four complexes. The values of bond degree (BD) have been calculated to evaluate the strength of interactions, suggesting that HEPOA ligand interacts more strongly with La and Nd than Er and Y. Investigations of the complexation of REs with phenoxyacetic acid-relate...

Thorium (Th) is a promising element that can be converted to fissile uranium for nuclear energy. A large amount of slag containing Th need to be effectively treated and stacked in rare earth (RE) industry. It is of importance to develop some novel processes for separating Th from REs using solvent extraction. The amide group was considered to have good selectivity for Th separation from REs. In order to solve the problem of RE entrainment during Th separation together with primary amine (N1923, (CnH2n+1)2CHNH2 n = 9–11) does not extract Th in hydrochloric acid system, three oxamic acid type extractants have been designed and synthesized in this paper. Among the extractants, the separation performance of 2-(dibenzylamino)-2-oxoacetic acid (DBOA) was indicated to be the best. As for the effective separation, the electron affinity of Th was larger, it was more preferred to coordinate with the extractant. The hydrogen ions released by the extractant could inhibit the extraction of REs rather than Th. Accordingly, Th could be separated from REs. Saponification process of oxamic acid extractant could be omitted in this separation process. By extracting Th using a lower concentration of oxamic acid selectively, not only the loss of RE could be reduced, but also a higher purity of Th could be obtained. Using a simplified fractional extraction experiment, the purity of RE in aqueous phase was increased to be 99.92% or higher, and the purity of obtained Th after stripping from loaded organic phase was increased to be 99.5%.