Response of Nd3+ and Sm3+ precipitating into rhabdophane and the leaching mechanism of associated monazite ceramics

Rhabdophane has been considered an important permeable reactive barrier to isolate groundwater radionuclides, and evaluating its precipitation response to different species of radionuclide in acid solutions is critical. In this work, the effects of pH values on the precipitation behavior of Nd³⁺ and Sm³⁺ into La-rhabdophane are systematically investigated. Some specific issues such as ions removal, precipitation reaction kinetics, and crystal growth affected ions incorporation are discussed in detail, along with uncovering the veil of the Ln (La, Nd, and Sm) leaching mechanism of associated La_0.666Nd_0.167Sm_0.167PO₄ monazite ceramic based on dissolution experiments and density functional theory. The results reveal that Nd³⁺ and Sm³⁺ can be removed more than 98% in pH = 1 solution within 12 h, whereas uneven precipitation process to form unexpected stoichiometric ratio of rhabdophane has been observed in 30–50 nm short crystal. Grain growth effects based on spark plasma sintering can contribute to homogenize the materials composition with obtaining La_0.666Nd_0.167Sm_0.167PO₄ monazite ceramics. Furthermore, the binding energy of Ln–O in (1 0 0) surface of monazite plays an important role in controlling the leaching stability of Ln³⁺, associated with the leaching activities are energetically favorable in the order of La > Nd > Sm for La_0.666Nd_0.167Sm_0.167PO₄ monazite.     

A theory of the formation of magnesium scales in sea water distillation plants,and means for their prevention

Some additives, which retard the formation of alkaline scale from sea water at temperatures up to 230°F, delay the precipitation of calcium carbonate but have no effect on the precipitation of magnesium hydroxide.Boiling aqueous solutions containing magnesium and bicarbonate ions or calcium/magnesium and bicarbonate ions produce an initial deposit of hydromagnesite (3MgCO₃·Mg(OH)₂·3H₂O) which converts on further heating to magnesium hydroxide. It is proposed that additives, to control magnesium scale formation, have to affect this intermediate.Crystals of calcite and hydromagnesite, produced in the presence of an additive which is effective in preventing alkaline scale formation, show marked distortion, tending to make the crystals larger and less regular in shape.     

ACIDS. PART 1. P,P"-DI(2-ETHYLHEXYL) METHANEDIPHOSPHONIC ACID

ABSTRACT

Two novel extractants, P,P'-di(2-ethylhexyl) methanediphosphonic acid (H2DEH[MDP]) and P.P'-dioctyl methanediphosphonic acid (H2DO[MDP]) have been synthesized at high purity and yield. H₂DEH[MDP] was selected for metal extraction studies because of its better physical properties. An investigation of the extraction of alkaline earth cations, Fe(III) and representative tri-, tetra- and hexavalent actinide ions from nitric acid solutions into o-xylene solutions of H₂DEH[MDP] at different concentrations was performed. With a few exceptions, the acid dependencies of the extraction of the above metal species strongly resembles those measured in the uptake of the same metals by the chelating ion exchange resin Diphonix®, which contains gem-diphosphonic acid groups chemically attached to a polymeric matrix. H₂DEH[MDP] exhibits practically no selectivity among the alkaline earth cations. The almost lack of acid dependency observed with Fe(lll) and tetra- and hexavalent actinides indicates that these ions are chelated by H₂DEH[MDP] mostly through the P=0 groups of the extractant. With Fe(lll) and the actinides, variable slopes of the extractant dependencies were measured, their values being strongly dependent on the acidity of the aqueous phase. Typically, the slope of the extractant dependency has a value of about two if the metal is extracted from high acidity solutions. This value becomes progressively lower as the aqueous acidity is reduced, tending to almost zero for acidities around 0.1 M. This phenomenon has been attributed to the formation of metal complexes having different stoichiometrics, ligand protonation and solubility in the aqueous phase.

H₂DEH[MDP] possesses an extraordinary affinity for actinides and Fe(III). In analogy with the Diphonix resin, this property can be exploited for actinide preconcentration and separation from complex matrices of analytical interest and from mixed waste solutions.     

Role of Nd3+ ions on the nucleation and growth of PbS quantum dots (QDs) in silicate glasses

The influence of Nd₂O₃ addition on the precipitation kinetics of lead chalcogenide (PbS) quantum dots (QDs) in silicate glasses was investigated. Energy dispersive X‐ray spectroscopy (EDS) indicated that the Nd³⁺ ions are preferentially located inside the PbS QDs rather than in the glass matrix. Changes in diameter (D) of PbS QDs exhibited smaller time dependencies (i.e., D≈t^{0.270‐0.286}) than that predicted by the classical Lifshitz–Slyozov–Wagner (LSW) theory. This is due to the limited concentrations of Pb²⁺ and S^2? ions and the large diffusion distance inside the glass matrix. In addition, extended X‐ray absorption fine structure (EXAFS) results indicated that the formation of PbS QDs was retarded due to the presence of Nd₂O₃ in the glasses, as the large NdO_x polyhedra interrupt the diffusion of Pb²⁺ and S^2? ions. We believe that these Nd³⁺ ions are primarily located in PbS QDs in the form of Nd–O clusters, and that the PbS QDs are built on top of these clusters.     

Direct Imaging of the Distribution of Nd3+ Ions in Glasses Containing PbS Quantum Dots

The influence of Nd³⁺ ions was investigated on the precipitation and optical properties of PbS quantum dots (QDs) inside silicate glasses. The diameters of the PbS QDs decreased as the concentration of Nd³⁺ in the glass increased as evidenced by blue shifts in the absorption and photoluminescence spectra. Electron energy loss spectroscopy shows that Nd³⁺ ions exist preferentially inside the PbS nanocrystals rather than in the glass matrix. We postulate that Nd–O clusters are preserved during heat treatment and serve as nucleation sites for PbS crystals. No change in the local bonding scheme of the Nd³⁺ ions was observed following heat treatment.     

Extraction of some Hexavalent Actinide Ions from Nitric Acid Medium using Several Substituted Diglycolamides

Several substituted diglycolamides, namely TPDGA, THDGA, TODGA, and TDDGA, were evaluated in a comparative study on the extraction of hexavalent actinide ions such as UO₂²⁺, NpO₂²⁺, and PuO₂²⁺ from nitric acid medium. The acid extraction constants (K_H) for the diglycolamides were determined to be 3.8 ± 0.6, 1.6 ± 0.1, 4.1 ± 0.4, and 1.4 ± 0.2 for TPDGA, THDGA, TODGA, and TDDGA, respectively. Though metal ion extraction generally increased with increasing the feed acid concentration, the nature of the extracted species changed with aqueous-phase acidity. While complexes of the type MO₂(NO₃)₂·nL (where L is the diglycolamide extractant and n is 1 and 2) were found to be extracted at 1 M HNO₃, the average number of ligand molecules associated with the complex decreased to ?1 when the nitric acid concentration increased to 3 M. These results have great significance from the actinide separation point of view, as the actinides ions can be made virtually inextractable by adjusting their oxidation state. The thermodynamic parameters were also calculated, which indicated spontaneous reactions with large exothermicities.     

Zirconia/garnet multiphase ceramics with high immobilization capacity for Nd confers better physical and chemical stability

Multiphase ceramics have a high application potential in the field of nuclear waste immobilization because of the efficient synergy between the individual phases. In this work, zirconia/garnet multiphase ceramics with high efficient and effective immobilization capacity of trivalent actinides were successfully prepared using conventional solid-phase sintering. ZrO₂ doping increases the lattice site available for nuclide substitution and advance the immobilization capacity of the ceramic substrate for nuclide. At the same time, the phase change of zirconia is used to tougher and improve the physical properties of the ceramic waste form. The feasibility of using multiphase ceramics for the efficient immobilization of trivalent actinides was assessed by studying the phase evolution, microstructure, Vickers hardness, and chemical stability of the multi-phase ceramics. Zr_1-xNd_xO_2-x/2/Ca_3-yNd_yZr_3-yFe_y-1Fe₃O₁₂ multiphase ceramics exhibited superior physical or chemical properties compared to most of the multiphase ceramics as well as the previously prepared single-phase calcium garnet ceramic waste forms. The Vickers hardness of all the multiphase ceramic samples ranged between 685 and 730 HV0.5. Under the condition of using simulate Bei Shan groundwater as leaching agent, the normalized leaching rates of Nd is approximately 10⁻6 g · m⁻² · day⁻¹, showing good chemical stability and achieving efficient and effective immobilization of trivalent actinides. The excellent chemical, as well as physical properties of Zr_1-xNd_xO_2-x/2/Ca_3-yNd_yZr_3-yFe_y-1Fe₃O₁₂ multiphase ceramics are expected to make them one of the substrates for more efficient and effective immobilizing of trivalent actinides.     

Microwave‐assisted Hydrothermal Synthesis of Single‐crystal Nanorods of Rhabdophane‐type Sr‐doped LaPO4·nH2O

A novel, simple, soft, and fast microwave‐assisted hydrothermal method was used for the preparation of single‐crystal nanorods of hexagonal rhabdophane‐type La_1?xSr_xPO_4?x/2·nH₂O (x = 0 or 0.02) from commercially available La(NO₃)₃·6H₂O, Sr(NO₃)₂, and H₃PO₄. The synthesis was conducted at 130°C for 20 min in a sealed‐vessel microwave reactor specifically designed for synthetic applications, and the resulting products were characterized using a wide battery of analytical techniques. Highly uniform, well‐shaped nanorods of LaPO₄·nH₂O and La_0.98Sr_0.02PO_3.99·nH₂O were readily obtained, with average length of 213 ± 41 nm and 102 ± 25 nm, average aspect ratio (ratio between length and diameter) of 21 ± 9 and 12 ± 5, and specific surface area of 45 ± 2 and 51 ± 1 m²/g, respectively. In both cases, the single‐crystal nanorods grew anisotropically along their c crystallographic‐axis direction. At 700°C, the hexagonal rhabdophane‐type phase has already transformed into the monoclinic monazite‐type structure, although the undoped and Sr‐doped nanorods retain their morphological features and specific surface area during calcination.     

Synthesis,crystal structures and NIR luminescence properties of binuclear lanthanide Schiff Base complexes

Three binuclear lanthanide complexes [Nd₂(L¹)₃(MeOH)]·MeOH·H₂O (1) and [Ln₂(H₂L²)₂(OAc)₄]·2(CF₃SO₃)·MeOH·EtOH (Ln = Nd (2) and Ho (3)) were prepared using two Schiff base ligands. Interestingly, 1 has a triple-decker structure with two lanthanide ions enclosed by three rigid conjugated Schiff base ligands (H₂L¹), while 2 and 3 show nanoscale ring structures (8 × 12 × 12 Å) formed by flexible long-chain Schiff base ligands (H₂L², ~ 23 Å) with the lanthanide ions located in the center. Upon excitation of the ligand-centered absorption bands, 1–2 and 3 show typical NIR emission spectra for Nd^3 + and Ho^3 + ions, respectively. In 1, the Nd(III) centers are shielded within the decker-like structure and surrounded by chromogenic Schiff base ligands (energy transfer donors). Luminescence studies show that the NIR emission lifetime of 1 is longer than that of 2 in solution.     

Ligand‐field splitting of the energy levels of Nd3+ (4f3) in 2‐hydroxyethyl methacrylate polymer (HEMA)

Detailed absorption spectra of trivalent neodymium (Nd³⁺) in 2‐hydroxyethyl methacrylate polymer (HEMA) are reported at cryogenic temperatures and at wavelengths between 440 and 900 nm. The Nd³⁺ spectra are confirmed by comparison with spectra of HEMA samples prepared without inclusion of the rare earth ion. The structure observed on the absorption bands can be interpreted in terms of the ligand‐field (crystal‐field) splitting of the energy levels of Nd³⁺ (4f³) for multiplet manifolds, ⁴F_3/2, ⁴F_5/2, ²H_9/2, ⁴F_7/2, ⁴S_3/2, ⁴F_9/2, ²H_11/2, ⁴G_5/2, ²G_7/2, ⁴G_7/2, and ²K_13/2. The Nd³⁺ ions are complexed as species made up of nitrate anions and H₂O molecules that come from the neodymium nitrate hydrate salt used in the preparation of the doped HEMA sample. The local symmetry of the Nd³⁺ ion in HEMA is very low (possibly C_S), and a number of different environments are likely for the neodymium species in the HEMA structure. We have calculated the ligand‐field splitting of the Nd³⁺ energy levels using a point charge/dipole model for one such possible species, Nd(NO₃)₃ · xH₂O^? (x = 5–6). The results of the model give an agreement of 10 cm^?1 (rms) between 43 observed‐to‐calculated ligand‐field (Stark) levels. Comparisons between these same calculated levels and observed levels obtained for Nd³⁺ in crystalline hydrated nitrate salts and certain Nd³⁺‐doped glasses also give good agreement and support a better understanding of the environment of Nd³⁺ in a polymeric structure. Copyright © 2006 Society of Chemical Industry     

Self-propagating high-temperature synthesis,phase composition and aqueous durability of Nd–Al bearing zirconolite-rich composites as nuclear waste form

ABSTRACT

In this study, the zirconolite-rich composite was rapidly synthesised from self-propagating high-temperature synthesis plus quick pressing using MoO₃ as the oxidant and Ti as the reductant. As a surrogate of trivalent actinides, Nd was introduced to substitute the Ca site of zirconolite and Al was employed as the charge compensator to replace the Ti site (nominally Ca_1?xNd_xZrTi_2?xAl_xO₇). The phase composition and Nd occupancy were analysed after Nd₂O₃ addition. Nd-bearing zirconolite was produced as the major ceramic phase. Nd mostly substitutes the Ca sites of zirconolite, which results in waste loading higher than 8.6?wt-% Nd. The aqueous durability of Nd–Al codoped sample (with 15?at.-% Nd substitutes the Ca site of zirconolite) was evaluated at 90°C as well. The 42 days normalised leaching rates of Mo, Ca and Nd were measured to be 3.70, 1.90?×?10^?2 and 3.46?×?10^?4?g?m^?2?d^?1.     

Diffraction Studies on Concentrated Aqueous Hydrochloric Acid Solutions

X-ray diffraction and neutron diffraction experiments with H/D isotopically substituted aqueous 21 mol% hydrochloric acid solutions were carried out in order to obtain detailed features concerning the intermolecular hydrogen-bonded structure in highly concentrated aqueous acidic solutions. Structure parameters, namely, intermolecular distance, root-mean-square amplitude, and coordination number, for the nearest neighbor H₃O⁺···H₂O interaction were determined from the least-squares-fitting analysis of the observed X-ray interference term. These were, respectively, r(H₃O⁺···H₂O) = 2.45(1) Å; l(H₃O⁺···H₂O) = 0.11(1) Å; and n(H₃O⁺···H₂O) = 1.8(1). The intermolecular nearest neighbor distances, r(H···H) = 2.02(5) Å and r(O···H) = 1.69(2) Å, were determined from the least-squares fit to partial structure factors, a_ij (Q), derived from the observed neutron intermolecular interference terms for sample solutions with different H/D isotopic ratios. The present values of intermolecular distances are significantly shorter than those for pure liquid water, implying that extremely strong hydrogen bonds exist in concentrated aqueous acidic solutions.     

Structural,morphological and optomagnetic properties of GO/Nd/Cu-Mn ferrite ternary nanocomposite

Graphene oxide (GO)/neodymium (Nd)/Cu_0·5Mn_0·5Fe₂O₄ ternary nanocomposite was prepared by sonochemical method and modified Hummer's method. The crystal structure and structural parameter of Cu_0·5Mn_0·5Fe₂O₄ (CMF) nanoferrites were changed with the addition of Nd³⁺ and GO. Raman active modes of the GO and ferrite system were observed from Raman spectra. The surface oxidation state (C 1s, O 1s, Cu 2p, Mn 2p, Fe 2p, and Nd 3 d) and their respective binding energies of the prepared nanocomposite were discussed. Different surface morphologies were acquired for CMF, Cu_0·5Mn_0·5Fe_1.85Nd_0.15O₄ (CMNF), GO, and GO/Cu_0·5Mn_0·5Fe_1.85Nd_0.15O₄ (GCMNF) ferrite nanocomposites. The absorption of the Cu-Mn nanoferrite (red region) shifted into the blue region with the addition of Nd³⁺ and GO. The magnetic parameters were changed with doping of Nd into CMF and GO in CMNF nanoferrite. It was found that the high anisotropy energy values of the CMNF and GCMNF ferrite nanocomposites could be used for electromagnetic wave-absorbing application.     

Effects of Nd Content on Structure and Chemical Durability of Zirconolite–Barium Borosilicate Glass‐Ceramics

The effects of Nd₂O₃ content (0–12 wt %) on crystalline phases, microstructure, and chemical durability of barium borosilicate glass‐ceramics belonging to SiO₂–B₂O₃–Na₂O–BaO–CaO–TiO₂–ZrO₂–Nd₂O₃ system were studied. The results show that the glass‐ceramics with 2–6 wt% of Nd₂O₃ possess mainly zirconolite and titanite phases along with a small amount baddeleyite phase in the bulk. Calcium titanate appears when the Nd₂O₃ content increases to 8 wt%, and the amount of quadrate calcium titanate crystals increases with further increasing content of Nd₂O₃. For the glass‐ceramics with 6 wt% Nd₂O₃ (Nd‐6), Nd elements homogeneously distribute in zirconolite, titanite, and residual glass phases. There is a strong enrichment of Nd in calcium titanate crystals for the sample with 10 wt% Nd₂O₃. The viscosity of Nd‐6 glass is about 49 dPa·s at 1150°C. Moreover, Nd‐6 glass‐ceramics show the lower normalized leaching rates of B (LR_B), Ca (LR_Ca), and Nd (LR_Nd) when compared to that of the sample with 8 wt% Nd₂O₃. After 42 days, LR_B, LR_Ca, and LR_Nd of the Nd‐6 glass‐ceramics are about 6.8 × 10^?3, 1.6 × 10^?3, and 4.4 × 10^?6 g·m^?2·d^?1, respectively.     

A novel three dimensional 3d–4f heterometallic coordination framework with 2, 2′-bipyridine-3-carboxylate and oxalate ligands

The 3D heterometallic polymeric complex 1 {[Nd₂Cu₂(L)₂ (OXA)₄·2(2H₂O)]·2(3H₂O)}_n (HL = 2, 2′-bipyridine-3-carboxyic acid, OXA = oxalate) was obtained from hydrothermal reaction of Nd₂O₃, Cu(ClO₄)₂, HL and oxalic acid in the presence of ethanol and water. X-ray single crystal diffraction investigation of the polymeric complexes {[Nd₂Cu₂(L)₂(OXA)₄·2(2H₂O)]·2(3H₂O)}_n exhibits an interesting and novel topological structure.     

The effect of Nd3+ concentration on fabrication,microstructure, and luminescent properties of anisotropic S-FAP ceramics

Nd³⁺ doped strontium fluorophosphate (S-FAP), with chemical formula Sr₅(PO₄)₃F, nanopowders were prepared using the co-precipitation method. The prepared powders had no impurity phase with a grain size of about 30 nm and the doping limit of Nd³⁺ ions in strontium fluorophosphate is about 9 at.%. The morphology and particle size were determined by the doping concentration of Nd³⁺. Anisotropic Nd: S-FAP transparent ceramics with different Nd³⁺ doping concentrations were fabricated successfully by the simple hot-pressing method. The grain size of prepared S-FAP transparent ceramics decreased first and then increased with the increase of Nd³⁺ concentration. The 2 at.% Nd: S-FAP ceramic presented the highest optical transmittance at all wavelengths range. The characteristic transitions from the ground state to the excited states of Nd³⁺ ions were observed from the absorption spectra, and the absorption cross-section was calculated at 3.71 × 10^–20 cm². The influence of Nd³⁺ ion concentration on luminescence intensity and fluorescence lifetime was studied under 796 nm excitation. The strong emission of ⁴F_3/2→⁴I_9/2 transition in Nd: S-FAP was calculated by Judd–Ofelt (J-O) theory.     

High capacity synergistic immobilization of simulated trivalent actinides by zirconia/zircon multiphase ceramics

Zircon (ZrSiO₄) ceramics are candidate waste form for immobilizing actinides. However, ZrSiO₄ with single phase suffers from the low actinides solubility. Herein, 0.2Zr_1-aNd_aO_2-a/2/Zr_1-bNd_bSiO_4-b/2 (0≤a+b ≤ 0.3) multiphase ceramics were fabricated and their actinides immobilization ability and aqueous stability were evaluated. The evolutions of phase and microstructure affected by Nd doping were investigated. 0.2Zr_1-aNd_aO_2-a/2/Zr_1-bNd_bSiO_4-b/2 ceramics with 0≤a+b?0.1 exhibited monoclinic ZrO₂, tetragonal ZrO₂ and ZrSiO₄ mixed phases, while monoclinic ZrO₂, tetragonal ZrO₂, ZrSiO₄ and Nd₂Si₂O₇ phases with 0.1≤a+b ≤ 0.3. The increase of lattice volume revealed the successful lattice immobilization of Nd by ZrO₂/ZrSiO₄. Due to synergistic immobilization effect, the Nd immobilization capacity of ZrO₂/ZrSiO₄ is up to 10 at%, which is higher than that of single-phase ZrSiO₄ (4 at%). Furthermore, the obtained ceramics waste form exhibited good compactness and excellent aqueous stability. The results indicated that zirconia/zircon multiphase ceramics can be a potential candidate waste form for actinides.     

Low charge compensator (Mg2+) causing a new REE-end 3O structure (REE=Rare Earth Element) and a different phase transformation in Nd3+ Co-doped zirconolite: Investigation by X-ray structural analysis

Zirconolite-derived structures have shown promising applications for the immobilization of high-level radioactive wastes, especially for minor actinides. This study evaluated the effect of magnesium (Mg, one of the main impurities in natural zirconolites) incorporation into zirconolite on structural evolution and neodymium (Nd, surrogates to minor actinides) solubility in the designed zirconolite matrix. X-ray diffraction results showed the phase transformation from zirconolite-2M to zirconolite-3O with increasing Mg²⁺ incorporated into the target structure. The lattice parameters of zirconolites, Ca_(0.99-2x)Nd_2xZrTi_(2-x)Mg_xO₇, also showed a linear relationship with the amount of Mg²⁺ being substituted. The Rietveld refinement results showed that Nd³⁺ preferred occupying the Ca sites, while Mg²⁺ substituted the Ti sites in 5-fold coordination (TiO₅). X-ray adsorption near edge spectroscopy further revealed that the ratio of TiO₅ and TiO₆ in the zirconolites decreased and less distortions of TiO₆ polyhedra were induced with increasing Mg²⁺ concentration in the zirconolites. Moreover, a new mineral phase (REE-end zirconolite-3O) with the chemical formula of NdZrTi_1.5Mg_0.5O₇ was reported in this study, and the single target phase was synthesized without the coexistence of perovskite. The combination of selected area electronic diffraction and Rietveld refinement revealed that the structure of NdZrTi_1.5Mg_0.5O₇ was similar with zirconolite-3O - Nd dominated Ca in the 8-fold coordinated site, and Mg occupied the Ti sites in both 4-fold and 5-fold coordination. This study demonstrates that the new crystalline structure explored from the process of magnesium incorporation into zirconolites can provide insights about the design and optimization of reliable waste forms for the immobilization of nuclear wastes.     

Synthesis,crystal structure and desulfurization properties of zig-zag 1D coordination polymer of copper(II) containing 4-methoxybenzoic acid ligand

ABSTRACT

Combustion of fuels containing organosulfur compounds has resulted in the emission of sulfur oxides (SO_x) into the atmosphere, therefore, causing serious environmental and health hazards. Herein, slightly distorted octahedral zig-zag 1D coordination polymer of copper(II) [Cu(4-mba)₂(H₂O)₃] was synthesized by reacting copper sulfate pentahydrate with a carboxylate-containing ligand (H-4mba?=?4-methoxybenzoic acid) and employed for sulfur compound uptake. The ligand coordinates to the copper(II) atom via two pairs of deprotonated ligating atoms (carboxylate oxygens) and two water molecules. Structural characterization also reveals that interplay of O–H···O, N–H···O, C-H···O and C–H···π interactions between lattice and coordinated water and ligands significantly contribute to the crystal packing leading to the formation and strengthening of three-dimensional supramolecular assembly. The complex, [Cu(4-mba)₂(H₂O)₃], show potential for desulfurization of fuel with an observed adsorption capacity of 9.6?mg/g at 32°C for 6?h. DFT calculations further revealed a transfer of electron sulfur-containing compounds and the complex, [Cu(4-mba)₂(H₂O)₃], thus leading to a stronger pi–pi interaction.     

UPTAKE OF METAL IONS BY A NEW CHELATING ION-EXCHANGE RESIN. PART 1: ACID DEPENDENCIES OF ACTINIDE IONS*

ABSTRACT

The uptake of several actinide ions [U(VI), Pu(IV), Np(IV), Th(IV] and Am(DI)) from nitric and hydrochloric acid solutions, and of U(VI) from near-neutral solutions by the new chelating ion-exchange resin, Diphonix^TM, has been investigated. Diphonix is a polyfunctional resin containing sulfonic and gem-diphosphonic acid groups chemically bonded in a styrene-divinylbenzene polymeric network. Comparison of the acid dependencies of the actinide ions uptake measured with Diphonix with those obtained using a commercial sulfonic -type resin and a resin containing both sulfonic and monophosphonic aCid groups, hat Shown that Diphonix binds the actinides via a different kind of chemical interaction, involving the.formation of chelate complexes through the phosphoryl groups of the gem-diphosphonic acids. As a consequence, Diphonix is superior to other resins in extracting actinide ions from very acidic solutions. A better performance of Diphonix is also observed with the uptake of uranium from neutral solutions. Conditions for efficient stripping of actinide species from the resin have been found.