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Open Access Publications from the University of California

Scholarly Works (7 results)

  • Article
  • Peer Reviewed
LBL Publications (2005)

Detection and quantification of the aquo ions of Pu in 1 M HClO4 was carried out using a 1-meter liquid core waveguide (LCW) coupled to a fiber optic UV-Vis spectrometer. Detection limits of 7 x 10-7 M for Pu(VI), 1.6 x 10-5 M for Pu(V), 5 x 10-6 M for Pu(IV) and 8 x 10-6 M for Pu(III) were achieved. The limits of detection represent increases of 18 to 33 times those achievable using a conventional 1-cm path length. Because of the much lower detection limits of the LCW, routine identification of the oxidation states in dilute Pu solutions can be made.

    Cover page: Detection and Quantification of Pu(III, IV, V, and VI) Using a 1.0-meter Liquid Core Waveguide
    • Article
    LBL Publications (2003)
      Cover page: Low-level detection and quantification of Plutonium(III, IV, V, and VI) using a liquid core waveguide
      • Article
      • Peer Reviewed
      Lawrence Berkeley National Laboratory (2005)
        Cover page: Soft x-ray scanning transmission x-ray microscopy (STXM) of actinide particles
        • Article
        • Peer Reviewed
        LBL Publications (2020)
        Gas-phase reactions of pentavalent metal dioxide cations MVO2+ with water were studied experimentally for M = V, Nb, Ta, Pr, Pa, U, Pu, and Am. Addition of two H2O can occur by adsorption to yield hydrate (H2O)2MVO2+ or by hydrolysis to yield hydroxide MV(OH)4+. Displacement of H2O by acetone indicates hydrates for PrV, UV, PuV, and AmV, whereas nondisplacement indicates hydroxides for NbV, TaV, and PaV. Computed potential energy profiles agree with the experimental results and furthermore indicate that acetone unexpectedly induces dehydrolysis and displaces two H2O from (H2O)VO(OH)2+ to yield (acetone)2VO2+. Structures and energies for several MV, as well as for ThIV and UVI, indicate that hydrolysis is governed by the involvement of valence f versus d orbitals in bonding: linear f-element dioxides are more resistant to hydrolysis than bent d-element dioxides. Accordingly, for early actinides, hydrolysis of ThIV is characteristic of a 6d-block transition metal; hydration of UV and UVI is characteristic of 5f actinyls; and PaV is intermediate between 6d and 5f. The praseodymium oxide cation PrVO2+ is assigned as an actinyl-like lanthanyl with properties governed by 4f bonding.
          Cover page: Hydrolysis of Metal Dioxides Differentiates d‑block from f‑block Elements: Pa(V) as a 6d Transition Metal; Pr(V) as a 4f “Lanthanyl”
          • Article
          • Peer Reviewed
          LBL Publications (2017)
          The synthesis, reactivity, structures, and bonding in gas-phase binary and complex oxide anion molecules of protactinium and uranium have been studied by experiment and theory. The oxalate ions, AnVO2(C2O4)-, where An = Pa or U, are essentially actinyl ions, AnVO2+, coordinated by an oxalate dianion. Both react with water to yield the pentavalent hydroxides, AnVO(OH)2(C2O4)-. The chemistry of Pa and U becomes divergent for reactions that result in oxidation: whereas PaVI is inaccessible, UVI is very stable. The UVO2(C2O4)- complex exhibits a remarkable spontaneous exothermic replacement of the oxalate ligand by O2 to yield UO4- and two CO2 molecules. The structure of the uranium tetroxide anion is computed to correspond to distorted uranyl, UVIO22+, coordinated in the equatorial plane by two equivalent O atoms each having formal charges of -1.5 and U-O bond orders intermediate between single and double. The unreactive nature of PaVO2(C2O4)- toward O2 is a manifestation of the resistance toward oxidation of PaV, and clearly reveals the disparate chemistries of Pa and U. The uranium tetroxide anion, UO4-, reacts with water to yield UO5H2-. Infrared spectra obtained for UO5H2- confirm the computed lowest-energy structure, UO3(OH)2-.
            Cover page: Revealing Disparate Chemistries of Protactinium and Uranium. Synthesis of the Molecular Uranium Tetroxide Anion, UO4 –
            • Article
            Lawrence Berkeley National Laboratory (2001)

            The sorption of Pu(VI) and Pu(V) onto manganite (MnOOH) and Hausmannite (Mn3O4) was studied at pH 5. Manganite sorbed 21-24 percent from a 1x10-4 M plutonium solution and the hausmannite removed between 43-66 percent of the plutonium. The increased sorption by hausmannite results from its larger surface area (about twice that of manganite) plus a larger number of active surface sites. X-ray absorption near-edge structure (XANES) spectra taken at the Pu LIII edge were compared to standard spectra of plutonium in single oxidation states. Based on these spectra, it appears that both manganite and hausmannite reduce the higher valent plutonium species to Pu(IV). Between 53-59 percent of the plutonium was present as Pu(IV) in the manganite samples while 55-61 percent of the plutonium complexed to the hausmannite had also been reduced to Pu(IV). The exact mechanism behind this redox interaction between the plutonium and the manganese needs to be identified.

              Cover page: Complexation and redox interactions between aqueous plutonium and manganese oxide interfaces
              • Article
              LBL Publications (2005)
                Cover page: Extraction of short-lived zirconium and hafnium isotopes using crown ethers: A model system for the study of rutherfordium
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