https://www.uclmail.net/users/r.steele/steele11a.pdf

Confirmation of mass-independent Ni isotopic variability in iron meteorites

Variations in the isotopic composition of Ni resulting from natural mass-dependent processes in terrestrial or extraterrestrial conditions, inhomogeneous distribution of nucleosynthetic components and/or ingrowth from radioactive parent nuclides, help us to further understand the early formation history of Solar System materials and the nature of the processes these materials subsequently experienced. In studies of Ni isotope systematics, mass-dependent variations in the isotopic composition of Ni are often bypassed because of the challenges associated with the sample preparation. At the level of natural variation studied, Ni isotope ratio measurements are extremely sensitive to spectral interference, artificial on-column isotope fractionation and possibly even to the mass bias correction model applied. To adequately address these complications, an isolation procedure and measurement protocol relying on multi-collector ICP-mass spectrometry (MC-ICP-MS) have been designed and validated in this work. The overall reproducibility obtained based on repeated measurement of a Sigma-Aldrich high-purity Ni standard is 0.036‰, 0.049‰, 0.078‰ and 0.53‰ for δ60/58Ni, δ61/58Ni, δ62/58Ni and δ64/58Ni, respectively (n = 14; 2 SD). Nickel isotope ratio variations have been studied in a set of iron meteorites and geological reference materials, and the results obtained, except for those suffering from an elevated 64Zn background, show good agreement with the available literature data. By using the flexible generalized power law with a variable discrimination exponent and the three-isotope method, the processes underlying natural mass fractionation of Ni for terrestrial reference materials were found to have a mixed equilibrium/kinetic nature. Mass-dependent Ni fractionation was observed between sample fractions of the Canyon Diablo iron meteorite, and the extracted fractionation factor β corresponds to isotope partitioning following the power law.

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Development of an isolation procedure and MC-ICP-MS measurement protocol for the study of stable isotope ratio variations of nickel

Nickel is an iron-peak element with 5 stable isotopes (see Table 1) which is both cosmochemically abundant and rich in the information carried in its isotopic signature. Significantly, 60Ni is the radiogenic daughter of 60Fe, a short-lived nuclide (t1/2 = 2.62 Ma; Rugel et al. 2009) of a major element. 60Fe has the potential to be both an important heat source and chronometer in the early solar system. 60Ni abundances serve to document the prior importance 60Fe and this is a topic of on-going debate (see Extinct 60 Fe and radiogenic 60 Ni ). The four other stable Ni nuclides span a sizeable relative mass range of ~10%, including the notably neutron-rich nuclide 64Ni. The relative abundances of these isotopes vary with diverse stellar formation environments and provide a valuable record of the nucleosynthetic heritage of Ni in the solar system (see Nucleosynthetic Ni isotopic variations ). Ni occurs widely as both elemental and divalent cationic species, substituting for Fe and Mg in common silicate structures and forming Fe/Ni metal alloys. The Ni isotope chemistry of all the major planetary reservoirs and fractionations between them can thus be characterized (see Mass-Dependent Ni isotopic Variability ). Ni is also a bio-essential element and its fractionation during low-temperature biogeochemical cycling is a topic that has attracted recent attention (see Mass-Dependent Ni isotopic Variability ).

### Notation

Much of the work into Ni has been cosmochemical, focussing on the nucleosynthetic origins of different meteoritic components. Such studies have primarily investigated mass-independent isotopic variations, both radiogenic and non-radiogenic, which require choosing a reference isotope pair for normalization. Throughout this work we use 58Ni–61Ni as the normalizing pair, in keeping with current practice in the field. An alternative 58Ni–62Ni normalization scheme has previously been used for bulk …

/pdf/the-isotope-geochemistry-of-ni-5ah8mqbm1h.pdf

The Isotope Geochemistry of Ni

Multi-walled carbon nanotubes (MWCNTs) were functionalized with diglycolamide (DGA) through chemical covalent route. The adsorption behavior of the DGA-functionalized-MWCNTs (DGA-MWCNTs) towards thorium from aqueous solution was studied under varying operating conditions of pH, concentration of thorium, DGA-MWCNTs dosages, contact time, and temperature. The effective range of pH for the removal of Th(IV) is 3.0–4.0. Kinetic data followed a pseudo-second-order model. The equilibrium data were correlated with the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. The equilibrium data are best fitted with Langmuir model. The equilibrium Th(IV) sorption capacity was estimated to be 10.58 mg g−1 at 298 K. The standard enthalpy, entropy, and free energy of adsorption of the thorium with DGA-MWCNTs were calculated to be 8.952 kJ mol−1, 0.093 kJ mol−1 K−1 and -18.521 kJ mol−1 respectively at 298 K. The determined value of sticking probability (0.072) and observed kinetic and isotherm models reveal the chemical adsorption of thorium on DGA-MWCNTs.

Adsorptive removal of thorium from aqueous solution using diglycolamide functionalized multi-walled carbon nanotubes

Extraction and separation of scandium from rare earths by electrostatic pseudo liquid membrane

From certain organic solvents containing organic phosphorus compounds such as trioctylphosphine oxide (TOPO), bis(2-ethylhexyl)orthophosphoric acid (HDEHP), or tri-n-butylphosphate (TBP) and hydrochloric acid, scandium is much less retained on the strongly acidic cation-exchange resin Dowex 50 than are all other members of the rare-earth group. Thus on this resin in a medium which is 95% tetrahydrofuran, 5% 6 M hydrochloric acid, and 0.1 M TOPO, the separation factor for scandium-rare earths is greater than 4 × 103 (corresponding to distribution coefficients of 4 × 103 for all the other rare-earth elements). By the use of this system a complete and highly effective separation of tracer and macro quantities of scandium from the rare earths can be achieved on a column of this exchanger. Among the organic solvents investigated, tetrahydrofuran gives the best results. The effectiveness of the organic extractants increases in the order TBP < HDEHP < TOPO

K.A. Orlandini

Papers

Cation-exchange separation of scandium from the rare-earth elements.

Cation-exchange separation of hafnium and zirconium from accompanying ions.

Cation exchange separation of thorium from rare earths and other elements in methanol-nitric acid medium containing trioctylphosphine oxide

Specific cation-exchange separation of nickel

Selective cation exchange separation of carrier-free cesium-137 and sodium-22