Studies on the radiolytic stability of N,N,N′,N′-tetra-2-ethylhexyl diglycolamide in n-dodecane solution containing different phase modifiers

The radiolytic stability of a branched diglycolamide extractant, namely N,N,N′,N′-tetra-2-ethylhexyl diglycolamide (T2EHDGA) dissolved in n-dodecane containing several phase modifiers, viz. N,N-dihexyloctanamide (DHOA), tri-n-butyl phosphate (TBP), 1-decanol and iso-decanol has been investigated. The distribution ratio of Am(III) decreased with increased radiation dose studied up to 1000 kGy. Nevertheless, all the composition of extractants showed satisfactory results up to 500 kGy, beyond which the extractants degraded drastically. The stripping behaviour of Am(III) with 0.2 M HNO₃ was found to be unaffected even with the ligand solution irradiated up to 1000 kGy. Extraction of fission product and structural elements was also investigated using the irradiated solvents and was found to be not significantly affected with increasing absorbed dose with the exception of Mo which showed sharp rise in the distribution coefficient values. Loading of Nd in the organic phase decreased with the irradiated solvent due to degradation of the carrier. The effect of the absorbed dose on physical parameters such as density, viscosity and interfacial tension of the solvents has also been investigated.     

Comparative evaluation of two substituted diglycolamide extractants for ‘actinide partitioning’

Extraction behaviour of actinides, lanthanides, fission products and structural elements has been studied with the two diglycolamide extractants, namely N,N,N′,N′-tetra-2-ethylhexyl diglycolamide (T2EHDGA) and N,N,N′,N′-tetraoctyl diglycolamide (TODGA). The acid extraction studies suggested that T2EHDGA (K_H: 1.8) is less basic as compared to its linear homologue, TODGA (K_H: 4.1). The distribution ratio of Am(III) by 0.1 M diglycolamides followed the order: TODGA > T2EHDGA. The number of ligand molecules present in the stoichiometry of the extracted species of Am(III) was found to be three and four for T2EHDGA and TODGA, respectively. Thermodynamics studies suggested that the extraction of Am(III) by both the extractants is exothermic in nature. The radiolytic stability of TODGA and T2EHDGA solutions in n-dodecane has been investigated. Due to lower distribution ratio of Am by T2EHDGA, 0.2 M of its solution has been used as compared to 0.1 M solution of TODGA. The distribution behaviour of various metal ions, viz. Am, Nd, Fe, Mo, Cr, Sr and Cs has been studied from nitric acid as well as from simulated high level waste solution.     

Extraction behavior of cerium by tetraoctyldiglycolamide from nitric acid solutions

The diamide N,N,N′,N′-tetraoctyldiglycolamide (TODGA) was synthesized and characterized. The prepared TODGA was applied for extraction of Ce(III) from nitric acid solutions. The equilibrium studies included the dependencies of cerium distribution ratio on nitric acid, TODGA, nitrate ion, hydrogen ion and cerous ion concentrations. Analysis of the results indicates that the main extracted species is Ce(TODGA)₂(NO₃)₃HNO₃. The capacity of Ce loading is approximately 45 mmol/L for 0.1 M solution of TODGA in n-hexane. Finally, the thermodynamic parameters were calculated: K (25 °C) = 3.8 × 10³, ΔH = −36.7 ± 1.0 kJ/mol, ΔS = −54.6 ± 3.0 J/K mol, and ΔG = −20.4 ± 0.1 kJ/mol.     

Preconcentration of uranium(VI) and thorium(IV) from aqueous solutions using low-cost abundantly available sorbent

Olive cake as low-cost abundantly available sorbent has been characterized by N₂ at 77 K adsorption, porosity analysis, elemental analysis and IR spectra and has been used for preconcentrating of uranium(VI) and thorium(IV) ions prior to their determination spectrophotometrically. The optimum pH values for quantitative sorption of U(VI) and Th(IV) are 4–7 and 3–7, respectively. The enrichment factor for the preconcentration of U(VI) and Th(IV) were found to be 125 and 75 in the given order. The sorption capacity of olive cake is in the range of 2,260–15,000 μg g⁻¹ for Th(IV) and in the range of 1,090–17,000 μg g⁻¹ for U(VI) at pH 3–7. The sorbent exhibits good reusability and the uptake and stripping of the studied ions were fairly rapid. The elution of U(VI) and Th(IV) was performed with 0.3–1 M HCl/1–2 M HNO₃ and 0.3–0.8 M HCl/1 M HNO₃, respectively. The precision of the method was 1.8 RSD% for U(VI) and 2.5 RSD% for Th(IV) in a concentration of 1.00 μg mL⁻¹ for 10 replicate analysis. The influence of some electrolytes and cations as interferents was discussed. Separation of U(VI) and Th(IV) from other metal ions in synthetic solution was achieved.     

A theoretical investigation on structures of tripodal thiourea derivatives and their anion recognition

The structural geometries of three tripodal thiourea receptors, i.e. 1,3,5-triethyl-2,4,6-tris[(N′-methylthioureido)methyl]benzene (1), tris[N′-methyl-N-(2-aminoethyl)thiourea]methane (2), tris[N′-methyl-N-(2-aminoethyl)thiourea]amine (3), and their complexes with F⁻, Cl⁻, Br⁻, I⁻, NO₃ ⁻, CO₃ ²⁻, SO₄ ²⁻, HSO₄ ⁻, PO₄ ³⁻, HPO₄ ²⁻ and H₂PO₄ ⁻ were obtained using the density functional theory calculations. Electronic and thermodynamic properties of anion binding complexes of the receptors 1, 2 and 3 were investigated. Recognition abilities of all the receptors in terms of selectivity coefficients are reported. Intermolecular interactions in all the studied complexes occurring via multi-point hydrogen bonding were found. The receptors 1, 2 and 3 were found to be excellent selectivity for phosphate ion and their binding free energy for the phosphate ion are −292.57, −291.77 and −295.01 kcal/mol, respectively.     

Mononuclear Rare Earth Metal Complexes based on 1,10-phenanthroline Derivatives as Catalysts for Hydrolysis of p-nitrophenyl Phosphate (NPP)

Two multidentate ligands: N,N′-di-(propionic acid-2′-yl-)-2,9-diaminomethyl-1,10-phenanthroline (L1) and N,N′-di-(3′-methylbutyric acid-2′-yl-)-2,9-diaminomethyl-1,10-phenanthroline (L2) were synthesized. The hydrolytic kinetics of p-nitrophenyl phosphate (NPP) catalyzed by complexes of L1 and L2 with La(III), Gd(III) have been studied. Both LnL and LnLH₋₁ have been examined as catalysis for the hydrolysis of NPP in aqueous solution at 298 K, I = 0.10 mol dm⁻³ KNO₃ at the pH range 7.4–9.1, respectively. Kinetic studies show that both LnL and LnLH₋₁ have catalytic activity, but LnLH₋₁ is more active than LnL in the hydrolysis of NPP. The second-order rate constants for the hydrolysis of NPP are k_GdL1H−1 = 0.01399 mol⁻¹ dm³ s⁻¹, k_GdL1 = 0.0000110 mol⁻¹ dm³ s⁻¹ for complexes GdL1H₋₁ and GdL1, respectively. A new mechanism was proposed for the hydrolysis of NPP catalyzed by LnL and LnLH₋₁.     

The role of Cherenkov and liquid scintilation counting in evaluating the anion-exchange separation of210Pb−210Bi−210Po

Using as eluent a sequence of 3M HCl, 12M HCl, and 8M HNO₃, a mixture of²¹⁰Pb,²¹⁰Bi, and²¹⁰Po may be clearly separated on a column of Dowex 1×2−100 anion exchange resin. A Cherenkov count in H₂O and the variation in count rate with time confirm that the nuclides emerge in the order²¹⁰Pb→²¹⁰Bi→²¹⁰Po. If 12M HCl is replaced by 1.5M H₂SO₄/2.3 M Na₂SO₄, a clean separation also results, but recovery of²¹⁰Po becomes considerably more difficult. All three nuclides are readily detectable by liquid scintillation counting, with the efficiency for²¹⁰Pb in the 60–70% range. The Cherenkov aqueous counting efficiency for²¹⁰Bi is ∼14–15%.     

Thermochemistry of some adducts of Indium(III) chloride with neutral donors

The [InCl₃(L) _n ] (where L is 2,2′-bipyridine (bipy), 2,2′-bipyridine N,N′-dioxide (bipyNO), N,N-dimethylacetamide (dma), urea (u), thiourea (tu) or 1,1,3,3-tetramethylthiourea (tmtu); n = 1.5, 3 or 4) were synthesized and characterized by melting points, elemental analysis, thermal analysis and IR spectroscopy. The enthalpies of dissolution of the adducts, Indium(III) chloride and ligands in 1.2 M aqueous HCl were measured and by using thermochemical cycles, the following thermochemical parameters for the adducts have been determined: the standard enthalpies for the Lewis acid/base reactions (Δ_r H ^θ), the standard enthalpies of formation (Δ_f H ^θ), the lattice standard enthalpies (Δ_M H ^θ), and the standard enthalpies of decomposition (Δ_D H ^θ).     

Study on mechanism for oxidation of <Emphasis Type="Italic">N,N</Emphasis>-dimethylhydroxylamine by nitrous acid

The oxidation of N,N-dimethylhydroxylamine (DMHAN) by nitrous acid is investigated in perchloric acid and nitric acid medium, respectively. The effects of H⁺, DMHAN, ionic strength and temperature on the reaction are studied. The rate equation in perchloric acid medium has been determined to be −d[HNO₂]/dt = k[DMHAN][HNO₂], where k = 12.8 ± 1.0 (mol/L)⁻¹ min⁻¹ when the temperature is 18.5 °C and the ionic strength is 0.73 mol/L with an activation energy about 41.5 kJ mol⁻¹. The reaction becomes complicated when it is performed in nitric acid medium. When the molarity of HNO₃ is higher than 1.0 mol/L, nitrous acid will be produced via the reaction between nitric acid and DMHAN. The reaction products are analyzed and the reaction mechanism is discussed in this paper.     

Extraction of molybdenum and technetium with diamides of dipicolinic acid from nitric acid solutions

The concentration of molybdenum(VI) in dissolved spent nuclear fuel is comparable with the concentrations of Tc, and the minor actinides (Np, Am). Therefore it is of great interest to understand its behavior under conditions imposed by separation processes. The simultaneous extraction ability of ortho, meta, and para isomers of N,N′-diethyl-N,N′-ditolyl-dipicolinamide (EtTDPA) for molybdenum and technetium were investigated in a large range of nitric and hydrochloric acid conditions. Molybdenum shows no increase in extraction at higher concentrations of nitric acid giving a solvate number n=0 with all isomers of EtTDPA, while Mo shows great extractability from HCl. Technetium distribution ratios decrease with increasing concentrations of nitrate showing indication of ion exchange occurring between TcO₄ ⁻ and NO₃ ⁻ anions. Et(m)TDPA and Et(p)TDPA show the greatest extractability, with 60% of the total technetium extracted into the organic phase at 1M HNO₃.     

Voltammetry of electroactive liquid redox systems: anion insertion and chemical reactions in microdroplets of para-tetrakis(6-methoxyhexyl) phenylenediamine, para- and meta-tetrahexylphenylenediamine

The effect of the structure of the organic precursor molecule on the electroinsertion of anions and on the formation of materials in the ionic liquid state is compared for three compounds, para-N, N, N′, N′-tetrahexylphenylenediamine (p-THPD), meta-N, N, N′, N′-tetrahexylphenylene diamine (m-THPD), and para-N, N, N′, N′-tetrakis(6-methoxyhexyl)phenylenediamine (p-TMHPD), by characterising their condensed phase voltammetric properties in aqueous media. The electrochemically driven anion insertion in p-THPD and p-TMHPD in the presence of ClO₄ ⁻, F⁻, Cl⁻, Br⁻, I⁻, and SO₄ ²⁻ is shown to be extremely sensitive to structure. The introduction of the methoxy end groups in p-TMHPD causes (1) a considerable shift to more negative electroinsertion potentials, (2) a less stable response which upon continuous cycling decreases, and (3) considerably lower anion selectivity. For the insertion of sulfate, only p-TMHPD yields an electrochemical response which is shown to be consistent with insertion of the dianion SO₄ ²⁻. The electrochemical oxidation of a deposit of m-THPD is accompanied by anion insertion and a chemical reaction step in an EC-type electrochemical process. The product of the chemical step is electrochemically active and results in a new reversible electroinsertion process. Starting materials and products of the microdroplet reactions are characterised by Maldi-TOF mass spectrometry and a reaction mechanism based on condensed phase polymerisation is proposed. Received: 15 November 1999 / Accepted: 2 December 1999     

Solvent extraction of hafnium(IV)

^{175, 181}Hafnium(IV) was extracted by HDBP in 2-ethylhexanol from 1–10M solutions of HClO₄, HCl and HNO₃, and 1–8M H₂SO₄. As with low polar organic phase diluents, the acidity dependence of the distribution ratio of Hf, D, passes through a minimum for HClO₄, HCl, and H₂SO₄ whereas only an increase of D can be observed with increasing HNO₃ concentration. From the slope analysis the following complexes were found to be extracted (HDBP=HA): HfA₄ at <4M HClO₄ and <5M HCl, lg K_extr=9, HfX₄(HA)₄ (X=ClO ₄ ⁻ , Cl⁻ or NO ₃ ⁻ ) at >5M HClO₄, >7M HCl and 1–10M HNO₃, Hf(SO₄)A₂(HA)_3–4 at <3M H₂SO₄, and Hf(SO₄)₂ (HA)₄ at >6M H₂SO₄. Coextraction of sulphate with hafnium from H₂SO₄ solutions was evidenced in experiments with macro concentrations of Hf(IV) and³⁵SO ₄ ²⁻ . Part XX: Coll. Czech. Chem. Commun., 40 (1975) 3617.     

Kinetic studies on H<Superscript>+</Superscript>-catalysed aquation of chromium(III)-oxalato-asparaginato and chromium(III)-oxalato-histidinato complexes

Three chromium(III) complexes with asparagine (Asn) and histidine (His) of the [Cr(ox)₂(Aa)]²⁻ type, where Aa = N,O–Asn, N,O–His or N,N′–His, were obtained and characterized in solution. The complexes with N,O–Aa undergo acid-catalysed aquation to give a free amino acid and cis-[Cr(ox)₂(H₂O)₂]⁻, whereas the complex with N,N′–His undergoes parallel reaction paths: (1) isomerization to the N,O–His complex and (2) liberation of an oxalate ligand. Kinetics of the N,O–Aa complexes in HClO₄ media were studied spectrophotometrically under pseudo-first-order conditions. The absorbance changes were attributed to the chelate ring opening at the Cr–N bond. The linear dependence of rate constants on [H⁺] was established, and a mechanism for the chelate ring cleavage was postulated. The existence of a metastable intermediate with O-monodentate Aa ligand was proved experimentally. Effect of [Cr(ox)₂(Aa)]²⁻ on 3T3 fibroblasts proliferation was studied. The tests revealed low cytotoxicity of the complexes. Complexes with Ala, His and Cys are good candidates for biochromium sources.     

Studies on the separation of 90Y from 90Sr by solvent extraction and supported liquid membrane using TODGA: role of organic diluent

Solvent extraction and supported liquid membrane transport studies on Y(III) and Sr(II) were carried out using both nitric as well as hydrochloric acid feed conditions using N,N,N′,N′-tetra-octyldiglycolamide (TODGA) in several organic diluents. The solvent extraction studies indicated extremely large separation factor (SF) values with chloroform, carbon tetrachloride, 1-decanol and hexone when 6 M HNO₃ was used as the feed. On the other hand, the SF values were 1–2 orders of magnitude lower when the nitric acid concentration was 3 M HNO₃. Significantly large SF values were also obtained from 6 M HCl when xylene, carbon tetrachloride, n-dodecane and hexone were used as the diluent. Though mass transfer was not very promising in the supported liquid membrane studies with most of the diluent systems, quantitative Y(III) transport was observed with 0.1 M TODGA in xylene with negligible Sr(II) transport suggesting possibility of obtaining carrier free ⁹⁰Y. The purity of the radiotracer was checked by half-life method.     

Adsorption behavior of 181W and 93mMo as lighter homologues of seaborgium (Sg) in HF/HNO3 on anion-exchange resin

Adsorption of carrier-free radiotracers ¹⁸¹W and ^93mMo produced in the ¹⁸¹Ta(p, n) and ^natNb(p, n) reactions, respectively, on anion-exchange resin was studied in mixed solution of HF and HNO₃ in a concentration range of 10⁻⁴–10⁻¹ M HF/0.1 M HNO₃. Distribution coefficients (K _d) of ¹⁸¹W and ^93mMo at 70 °C showed the V-shaped variation with the minimum at around 10⁻¹ M HF/0.1 M HNO₃, although variation of the K _d values for ^93mMo was quite small compared with that for ¹⁸¹W. Formation of oxofluoro complexes for W and Mo is briefly discussed.     

A bimetallic cyano-bridged complex based on nickel(II) and pentacyanidonitrosylferrate(II) precursors: characterization, crystal structure, and magnetic properties

A heterobimetallic cyano-bridged 1D coordination polymer of the composition [Ni(baepn)(μ-NC)Fe(CN)₃(NO)(μ-CN)]_n·3H₂O has been synthesized by the reaction of nickel(II) nitrate hexahydrate, baepn (baepn = N, N′-bis(2-aminoethyl)-1,3-propanediamine), and sodium nitroprusside dihydrate in a methanol–water mixture. The complex was characterized by physicochemical and spectroscopic methods. The crystal structure was established by single-crystal X-ray diffraction analysis. It reveals cyano-bridged heterometallic chains consisting of alternating arrays of Ni(II) and Fe(II) atoms, both being embedded in distorted octahedral environments. Low-temperature susceptibility measurements show the presence of weak antiferromagnetic exchange interactions between paramagnetic Ni(II) centers (J = −0.46 cm⁻¹) through long diamagnetic [Fe(CN)₅(NO)]²⁻ bridges. Spin state of the iron atom was established by ⁵⁷Fe M?ssbauer spectroscopy.     

Liquid-liquid extraction of protactinium(V) using tri-iso-octylamine

Solvent extraction of protactinium with tri-iso-octyl-amine (TIOA) in xylene, benzene, carbon tetrachloride and chloroform from HCl, HF, HNO₃, HClO₄ and H₂SO₄ media was studied using ²³³Pa as a radiotracer. The extraction efficiencies of protactinium were determined as a function of shaking time, concentrations of mineral acids in aqueous phase, extractant concentrations and diluents in organic phase. The extraction mechanism was discussed. The results show that the extracted species in the organic phase is [(R₃N⁻H)_nPa(OH)_xCl _y ^5−x−y ].     

Studies on the Synthesis and Thermodynamic Stability of Two Multidentate Ligands 2,9-disubstituted 1,10-phenanthroline

Two multidentate ligands: N,N′-di-(propionic acid-2′-yl-)-2,9-di-aminomethylphenanthroline (L₁) and N,N′-di-(3′-methylbutyric acid-2′-yl-)-2,9-di-amino-methylphenanthroline (L₂) were synthesized and fully characterized by ¹H NMR and elemental analysis. The binding ability of L₁ and L₂ to metal ions such as M(II) (M = Cu, Zn, Co and Ni) and Ln(III) (Ln = La, Nd, Sm, Eu, and Gd) has been investigated by potentiometric titration in aqueous solution and 0.1 mol dm⁻³KNO₃ at 25.0 ± °C. In view of the structure of L₁ and L₂, mononuclear metal complexes can be formed in solution. The stability constants of binary complexes of ligands L1 and L2 with metal ions M(II) and Ln(III) have been determined respectively and further discussed.     

Solvent extraction of calcium and strontium into nitrobenzene by using a synergistic mixture of hydrogen dicarbollylcobaltate and N,N,N′,N′-tetraisobutyl-2,6-dipicolinamide

Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of N,N,N′,N′-tetraisobutyl-2,6-dipicolinamide [T(iBu)DPA, L] has been investigated. The equilibrium data have been explained assuming that the species HL⁺, HL₂ ⁺, CaL₂ ²⁺, SrL₂ ²⁺ and SrL₃ ²⁺ are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene saturated with water have been determined.     

Studies on the Synthesis and Potentiometric Properties of Three Novel Tripodal Ligands and their Complexes

Three novel tripodal ligands, N,N′,N′′-tri-(3′-phenylpropionic acid-2′-yl-)-1,3,5-triaminomethylbenzene (Ll), N,N′,N′′-tri-(4′-methylvaleric acid-2′-y1-)-1,3,5-triaminomethylbenzene (L2) and N,N′,N′′-tri-(3′methylvaleric acid-2′-yl-)-1,3,5-triaminomethylbenzene (L3), have been synthesized and fully characterized. The stabilizing ability of complexes of the three ligands with transition metal ions Cu(II), Ni(II), Zn(II) and Co(II) and rare earth metal ions La(III), Nd(III), Sm(III), Eu(III) and Gd(III) has been investigated by the pontentiometric method in water and in aqueous KNO₃ (0.1 mol dm⁻³) at 25.0±0.1 °C, respectively. The results show that there is a great deal of difference between two series of complexes’ stabilities. An explanation of the difference has been given.