Combined cation-exchange and extraction chromatography for the concomitant separation of Zr, Hf, Th, and the Lanthanides from geological materials

A new method was developed, aiming to overcome the iron and titanium interferences which severely limit the applications of a recently introduced extraction chromatography material, referred to as RE resin (formerly, RE Spec), to the analysis of geological samples. The separation scheme is based on the combined use, in tandem columns, of the conventional AG50WX4 cation-exchange resin and the RE extraction chromatography material, without any intervening evaporation step. The Lanthanides are recovered quantitatively, while recoveries for Zr, Hf and Th range from 94 to 98%. These three elements are determined using the isotope dilution method, thereby alleviating the need for a yield correction. Compared with conventional methods based on cation-exchange, this combined scheme offers a greater multi-element capability, significant miniaturisation, acid wastes reduction, and a higher degree of purity of the separated analytes with regard to unwanted elements such as Ba and residual Ca and Al. This concomitant isolation of 17 trace elements of great interest in the Earth and Environmental Sciences, achieved with excellent recoveries and satisfactory blank levels, can be used prior to high precision analysis of ultra-trace elements in geological samples by ICP-Mass Spectrometry.     

Zirconium and hafnium hydrogen monothiophosphates, H2Zr(PO3S)2 and H2Hf(PO3S)2. Syntheses and selective ion-exchange properties of sulfur-containing analogues of H2M(PO4)2 (M = Zr, Hf)

The reactions between aqueous solutions of M4+ (M = Zr, Hf) and PO3S3- each result in the precipitation of a white gel that can be dried to a powder. Elemental analysis results for the white polycrystalline product yield a stoichiometry of H2M(PO3S)2. These new compounds are characterized by thermal analysis (DSC, TG-MS), vibrational spectroscopy (FT-IR, FT-Raman), 31P MAS NMR spectroscopy, energy-dispersive spectroscopy (EDS), and powder X-ray diffraction (XRD). On the basis of the characterizations and the results of trialkylamine intercalation experiments, we conclude that the H2M(PO3S)2 compounds have a layered structure that is likely similar to that of alpha-H2Zr(PO4)2.H2O. The interlayer spacing for both H2M(PO3S)2 compounds, determined by XRD, is approximately 9.4 A. Our characterization results suggest that the sulfur atom of each PO3S3- group is preferentially pointed into the interlayer region of the compound and is protonated. Two of the many potentially interesting properties of H2Zr(PO3S)2, its ion-exchange capacity and selectivity, are investigated. H2Zr(PO3S)2 is demonstrated to be an effective and recyclable ion-exchange material for both Zn2+(aq) and Cd2+(aq). Mass balance experiments indicate that the removal of Cd2+(aq) and Zn2+(aq) ions by solid H2Zr(PO3S)2 occurs by an ion-exchange process. Ion exchange results in the formation of the new compounds H0.2Cd0.9Zr(PO3S)2 and H0.50Zn0.75Zr(PO3S)2. The extraction of metal ions is monitored by XRD, vibrational spectroscopy, and elemental analysis. H2Zr(PO3S)2 reversibly intercalates Zn2+(aq) ions through three complete cycles of intercalation and deintercalation without any loss of ion-exchange capacity.     

Anion-exchange behaviour of 12 elements in H2SO4 and HF−H2SO4 medium

Anion-exchange data have been obtained for the elements As, Hf, Mo, Nb, Pa, Re, Sb, Sn, Ta, Tc, W, and Zr in 0.1 to 10M H₂SO₄ and in HF–H₂SO₄ mixtures of combination extending from 0.1 to 10M HF and from 0.1 to 10M H₂SO₄. The distribution ratios for mixed solutions are presented in form of adsorption contour lines.     

Kinetic stability of tetrazaporphin in binary H2SO4-AcOH and H2SO4-DMSO solutions

The state and kinetic stability of tetrazaporphin (I) in acetic acid and in dimethyl sulfoxide (DMSO) in the presence of H₂SO₄ were investigated. Partial protonatiqn of I to give I-AcOH₂ associates occurs in acetic acid. The kinetic parameters of the reaction involving the destruction of tetrazaporphin in the presence of H₂SO₄ in acetic acid and DMSO solutions were determined. The mechanism of the destruction is discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 932–936, July, 1984.     

Dynamics of vibrational overtone excitations of H2SO4, H2SO4-H2O: hydrogen-hopping and photodissociation processes

Photochemical processes of sulfuric acid (H2SO4) and sulfuric acid monohydrate (H2SO4-H2O) following overtone excitation of the OH stretching mode are studied by classical trajectory simulations using the semiempirical PM3 potential suface in "on the fly" calculations. The main results are the following: (1) In the excitation of H2SO4 to the fifth OH-stretch overtone, hopping of the H atom between oxygen atoms is found to take place in 22% of the trajectories, only once during simulations of 400 ps. (2) All the trajectories for H2SO4 show a rapid cis-trans isomerization. (3) The photolysis of H2SO4 into SO3 + H2O takes place in 5% of the trajectories on a time scale of approximately 9 ps. (4) Only low overtone levels of H2SO4-H2O have sufficiently long lifetimes to be spectroscopically relevant. Excitation to these OH stretching overtones is found to result in the dissociation of the cluster. H hopping or dissociation of H2SO4 does not take place.     

Substituent effect on geometric and electronic structure of benzenesulfonic acid: gas-phase electron diffraction and quantum chemical studies of 4-CH3C6H4SO3H and 3-NO2C6H4SO3H molecules

A combined gas-phase electron diffraction/mass-spectrometric and quantum chemical (B3LYP/cc-pVTZ, MP2/cc-pVTZ) study of the molecular structures of para-methylbenzenesulfonic acid (4-MBSA) and meta-nitrobenzenesulfonic acid (3-NBSA) was carried out. On the basis of mass spectrometric analysis, it was found that the substituted benzenesulfonic acids are thermostable at least up to 431(3) K. The fragmentations of 4-MBSA and 3-NBSA molecules under electron impact were analyzed. Quantum chemical calculations show that the 4-MBSA molecule exists as an enantiomeric pair, which is formed as a result of rotation of OH group about the S–O(H) bond. The 3-NBSA molecule has two conformers with different orientations of the O–H bond with respect to the nitro group and two corresponding enantiomers. The equilibrium configurations of 4-MBSA and both conformers of 3-NBSA have similar structures of the SO₃H group, with the O–H bond eclipsing one of the S=O bonds. Selected experimental bond distances for 4-MBSA/3-NBSA are (Å) r _h1(C–C)_av = 1.403(3)/1.395(4); r _h1(C–S) = 1.765(5)/1.784(5); r _h1(S=O)_av = 1.433(4)/1.438(4); and r _h1(S–O) = 1.618(4)/1.620(4). The potential functions for the internal rotation of SO₃H, OH, and CH₃ or NO₂ groups were calculated, and the transition states between enantiomers (conformers) were determined. The influence of substituent's nature on molecular geometry as well as on the energies of frontier orbitals and red-ox properties of the compounds is discussed. The inductive and mesomeric substituent effects were estimated from the donor–acceptor interaction energies of the natural bond orbitals of substituent and benzene frame. The correlation between group electronegativities and cooperative energetic characteristics of inductive and mesomeric effects of substituents is shown.     

X-Ray contrast media. Synthesis of esters of 3,5-diiodopyrid-4-one-N-acetic acid in the presence of KU-2 cation-exchange resin

In a study of the esterification of 3, 5-diiodopyrid-4-one-N-acetic acid with alipathic alcohols in the presence of KU-2 cation-exchange resin as catalyst, it was established that the reaction takes place readily and smoothly and gives the corresponding esters in high yields.     

Ab initio vibrational calculations for H2SO4 and H2SO4 x H2O: spectroscopy and the nature of the anharmonic couplings

Vibrational frequencies for fundamental, overtone, and combination excitations of sulfuric acid (H2SO4) and of sulfuric acid monohydrate cluster (H2SO4 x H2O) are computed directly from ab initio MP2/TZP potential surface points using the correlation-corrected vibrational self-consistent field (CC-VSCF) method, which includes anharmonic effects. The results are compared with experiment. The computed transitions show in nearly all cases good agreement with experimental data and consistent improvement over the harmonic approximation. The CC-VSCF improvements over the harmonic approximation are largest for the overtone and combination excitations and for the OH stretching fundamental. The agreement between the calculations and experiment also supports the validity of the MP2/TZP potential surfaces. Anharmonic coupling between different vibrational modes is found to significantly affect the vibrational frequencies. Analysis of the mean magnitude of the anharmonic coupling interactions between different pairs of normal modes is carried out. The results suggest possible mechanisms for the internal flow of vibrational energy in H2SO4 and H2SO4 x H2O.     

Synthesis and structure of (Ph4P)2MCl6 (M = Ti, Zr, Hf, Th, U, Np, Pu)

High-purity syntheses are reported for a series of first, second, and third row transition metal and actinide hexahalide compounds with equivalent, noncoordinating countercations: (Ph(4)P)(2)TiF(6) (1) and (Ph(4)P)(2)MCl(6) (M = Ti, Zr, Hf, Th, U, Np, Pu; 2-8). While a reaction between MCl(4) (M = Zr, Hf, U) and 2 equiv of Ph(4)PCl provided 3, 4, and 6, syntheses for 1, 2, 5, 7, and 8 required multistep procedures. For example, a cation exchange reaction with Ph(4)PCl and (NH(4))(2)TiF(6) produced 1, which was used in a subsequent anion exchange reaction with Me(3)SiCl to synthesize 2. For 5, 7, and 8, synthetic routes starting with aqueous actinide precursors were developed that circumvented any need for anhydrous Th, Np, or Pu starting materials. The solid-state geometries, bond distances and angles for isolated ThCl(6)(2-), NpCl(6)(2-), and PuCl(6)(2-) anions with noncoordinating counter cations were determined for the first time in the X-ray crystal structures of 5, 7, and 8. Solution phase and solid-state diffuse reflectance spectra were also used to characterize 7 and 8. Transition metal MCl(6)(2-) anions showed the anticipated increase in M-Cl bond distances when changing from M = Ti to Zr, and then a decrease from Zr to Hf. The M-Cl bond distances also decreased from M = Th to U, Np, and Pu. Ionic radii can be used to predict average M-Cl bond distances with reasonable accuracy, which supports a principally ionic model of bonding for each of the (Ph(4)P)(2)MCl(6) complexes.     

Contact Deposition of Copper Powders onto Zinc in H2SO4-CuSO4 and H2SO4-CuSO4-ZnSO4 Solutions and Their Morphology

The contact extraction of copper in the form of dispersed powders onto compact zinc from H₂SO₄-CuSO₄ and H₂SO₄-CuSO₄-ZnSO₄ solutions was studied. The influence exerted by acidity and temperature of the solution on the rate and time of cementation, specific consumption of metallic zinc, and morphology of copper deposits was investigated.