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For the adsorption and recovery of rare earth elements from aqueous nitric acid, solid-phase extraction resins were prepared by impregnating and immobilizing of bis(2-ethylhexyl)phosphoric acid extractant into the macroporous silica-based polymeric (SiO2-P) particles. It was found that bis(2-ethylhexyl)phosphoric acid/SiO2-P had higher adsorption distribution coefficient for heavy rare earth elements than for light rare earth elements. The adsorption capacity of Gd(III) was observed to be 0.315 mmol g-1 by bis(2-ethylhexyl)phosphoric acid/SiO2-P in 0.1M HNO3 at 298 K, which increased slightly when increasing temperature from 298 to 323 K. The adsorption isotherms of Gd(III) matched well with the Langmuir and Freundlich models. The obtained thermodynamic parameters (ΔH° and ΔG°) showed that the adsorption of Gd(III) by bis(2-ethylhexyl)phosphoric acid/SiO2-P was a spontaneous and exothermic process. This study also evaluated the chemical stability of bis(2-ethylhexyl)phosphoric acid/SiO2-P treated with nitric acid at different temperatures and demonstrated that bis(2-ethylhexyl)phosphoric acid/SiO2-P had considerable stability against nitric acid and heat. [ABSTRACT FROM AUTHOR]

Helium ion (He+) beam produced by a heavy ion linear accelerator was used to simulate α-rays for studying the radiation effect on 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid ([C4mim][NTf2]). The water-soluble radiolytic products of [C4mim][NTf2] under He+ beam irradiation were analysed, and it was found that they were similar to those by γ-ray irradiation, but their amount was much less than that by γ-ray irradiation, which was attributed to the recombination of [C4mim][NTf2] radical cations in track by high linear energy transfer (LET) radiations of the He+ beam. The extracting behaviour of Dy3+ using irradiated [C4mim][NTf2] in combination with alkylated bis-triazinyl-pyridine (CA-BTP) was assessed, and found that the influence of He+ beam on the extraction was less than that of γ-ray irradiation. In addition, radiolytic products have a different influence on Dy3+ extraction at different doses; Dy3+ partitioning decreases at 50 kGy due to the protonation of CA-BTP and the inhibition of cation exchange mechanism by radiation-formed hydrogen ions. The abnormal increase of Dy3+ partitioning at 100 kGy is mainly attributed to the precipitation formed between Dy3+ and radiolytic products (F- and SO3 2-). [ABSTRACT FROM AUTHOR]

Eu(III) was selectively reduced to Eu(II) at three-dimensional glassy carbon cathode in 0.01 mol · dm-3 hydrochloric acid medium. Eu(III) reduction took place after all the dissolved oxygen was reduced and then proceeded steadily. Separation of Eu(II) from trivalent rare earths (La, Ce, Sm, Gd, Er, Yb) was carried out using a novel impregnated resin based on bis(2-ethylhexy1)phosphoric acid. Eu(II) showed much lower affinity towards the resin than the trivalent rare earths and broke through the column readily. Eu of purity higher than 99.8% was yielded. The back-oxidation of Eu(II) was observed during the sorption and Eu(III) was absorbed onto the resin. Adsorbed light and middle rare earths could be stripped from the loaded resin by 3M hydrochloric acid. Stripping of heavy rare earths (Er, Yb) was problematic. [ABSTRACT FROM AUTHOR]

1,3-[(2,4-Diethyl-heptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) is a supramolecular compound exhibiting Cs ion recognition in high level liquid waste (HLLW). To separate effectively Cs(I) from HLLW, a novel silica-based Calix[4]arene-R14 polymeric material (Calix[4]arene-R14/SiO2-P) was prepared. It was done through impregnating a mixture of Calix[4]arene-R14 and tri-n-butyl phosphate (TBP), a molecular modifier, into the pores of macroporous SiO2-P particles utilizing a vacuum sucking technique. The sorption of some typical fission product (FP) elements Na(I), K(I), Cs(I), Rb(I), Sr(II), and La(III) towards Calix[4]arene-R14/SiO2-P was investigated by examining the influence of contact time and the HNO3 concentration. It was found that with an increase in the HNO3 concentration from 1.0 M to 4.0, the sorption of Cs(I) towards Calix[4]arene-R14/SiO2-P increased quickly and then decreased with further increase of HNO3 concentration to 5.0 M. At the optimum HNO3 concentration of 4.0 M HNO3, the Calix[4]arene-R14/SiO2-P adsorbent exhibited excellent sorption ability and selectivity for Cs(I) over all of the tested elements, which showed very weak or almost no sorption except Rb(I). The chromatographic separation of Cs(I) from a simulated HLLW containing ∼5 mM of the FP elements and 4.0 M HNO3 was performed by Calix[4]arene-R14/SiO2-P packed column at 298 K. Na(I), K(I), Sr(II), and La(III) were found to elute facilely and flowed into the effluent along with 4.0 M HNO3. Cs(I) and Rb(I), adsorbed strongly onto Calix[4]arene-R14/SiO2-P, were desorbed sufficiently by water. The leakage behavior of Calix[4]arene-R14 and TBP from Calix[4]arene-R14/SiO2-P was also investigated. [ABSTRACT FROM AUTHOR]

Diethylenetriaminepentaacetic acid (DTPA), a multi-dentate acidic chelating agent containing five carboxyl and three amine groups all capable of protonation, is a pentabasic acid. To separate minor actinide [MA(III)] and rare earth [RE(III)] elements effectively from a HNO3 solution containing DTPA generated in the MAREC process, a functional polymeric composite impregnated with a novel macroporous silica-based diglycolamide compound, N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA), was prepared. Thus, the impregnated functional polymeric composite (TODGA/SiO2-P) was obtained by impregnating and immobilizing TODGA molecules in the pores of the SiO2-polymer (SiO2-P) particles (ca. 50 μm diameter) via a vacuum sucking technique. The effects of H+ ions within the concentration range 0.01-3.0 M and of NO3- ions within the range 0.1-3.115 M on the adsorption of RE(III) ions onto TODGA/SiO2-P were investigated at 298 K. It was found that in the presence of 0.05 M DTPA, the DTPA species strongly affected the adsorption of RE(III) ions. The adsorption capability of TODGA/SiO2-P depended on the competitive reactions of RE(III) ions with two species, viz. H4DTPA- and H2DTPA3-. The distribution coefficient (Kd) for RE(III) ions increased with increasing NO3- concentration, with one RE(III) ion reacting with two NO3- ions. The adsorption mechanism of RE(III) ions towards the TODGA/SiO2-P polymeric composite in HNO3 solution containing 0.05 M DTPA was suggested as: RE3+ H4DTPA- + 2NO3- + 3TODGA/SiO2-P ⇌ RE(H4DTPA)(NO3)2•3TODGA/SiO2 The formation of H4DTPA- and RE(H4DTPA)(NO3)2 which are both capable of adsorbing with TODGA/SiO2-P was the main reason why RE(III) ions exhibited such significant adsorption in the presence of 0.05 M DTPA. [ABSTRACT FROM AUTHOR]

Electro‐oxidation of Ce(III) to Ce(IV) in nitric acid media at different anode materials with high oxygen evolution overpotential was carried out. Ce(IV) nitrato complexes were adsorbed on a novel resin, based on porous silica beads with immobilized polystyrene/DVB copolymer, that was impregnated with tri‐n‐butyl phosphate (TBP). Under the studied conditions, Ce(IV) sorption increased with increasing nitric acid concentration (0.5–6 mol · dm -3 ). Oxidation of sorbent by adsorbed Ce(IV) species resulting in Ce(III) release to the solution was observed and thoroughly evaluated. In spite of problems with TBP leakage (12%), column separation of pure Ce(IV) from Y(III) and La(III) was achieved in 6 mol · dm -3 HNO 3 at 288 K. Ce(IV) breakthrough capacity was 0.48 mol · kg -1 ‐TBP. Column regeneration with 0.1 mol · dm -3 nitric acid yielded Ce solution with purity higher than 99.99 wt.% with respect to La and Y impurities. [ABSTRACT FROM AUTHOR]

The ERIX process consists of electroreduction and anion exchange for reprocessing spent nuclear fuels, in which Pd removal from spent fuel solution is necessary in the first step, since Pd can deposit at the electrode in the metallic state and interfere with the electroreduction. In the present work, the possibility in selective removal of Pd using a porous silica‐supported anion exchanger, SiPyR‐N3, containing a pyridine group has been studied. Adsorption behavior of Pd(II) from a simulated solution using a SiPyR‐N3 packed column has been investigated. The elution of Pd(II) using 0.05 M DTPA and 0.2 M thiourea was examined and compared. The SiPyR‐N3 resin showed a significantly strong adsorption for Pd(II) from HNO 3 solution. The unique adsorption was considered to result from the complex formation between Pd(II) and the resin which contains the soft‐atom N with a lone pair of electrons. U(VI) and some typical simulated fission products, La(III), Pr(III), and Sr(II), showed almost no or very weak adverse impact on the Pd(II) separation, except for Re(VII) and Ru(III). The results of column experiments demonstrated that the Pd can be selectively removed from the nuclear spent fuel solution, though further work is needed to improve Pd elution. [ABSTRACT FROM AUTHOR]