Adsorption of actinides on cement compounds

Altenhein-Haese, C.; Bischoff, H.; Fu, Longsheng; Mao, Juan; Marx, G.

doi:10.1016/0925-8388(94)90986-5

Cited by 15 publications

(4 citation statements)

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“…The bond dissociation energies (BDEs) in Tables and indicate that BDEs for actinide-fluorine bonds are generally greater than for carbon–fluorine bonds, and that the An–F bond strength decreases somewhat from An = U to Np to Pu. High actinide halide BDEs, BDE[An–X] (An = U, Np, Pu; X = F, Cl, Br), have been demonstrated by the ability of bare An + ions to abstract halogens from halogenated hydrocarbons. , A particular area of interest is complexes that comprise the actinyls, AnO 2 2+ , bound to one or more halide: AnO 2 X n (2‑ n )+ . ,− One motivation for studying such simple complexes is that the effective electron donation of halides to the actinide metal center affects the axial actinide-oxygen bonds, generally weakening them. − Uranyls, both U VI (unless otherwise specified the oxidation states hereafter are An VI ) and U V , have been shown to form various halide complexes in condensed and gas phases, , including as representative examples UO 2 X 3 – (X = F, Cl, Br, I), ,, UO 2 F n (2‑ n )+ ( n = 1–4), − UO 2 Br 4 2– , U V O 2 X (X = Cl, I), and UO 2 X 2 (X = Cl, Br) . It has been established that the complexation affinities of uranyl by halides decreases in the order F – > Cl – > Br – .…”

Section: Introductionmentioning

confidence: 99%

Halide Abstraction from Halogenated Acetate Ligands by Actinyls: A Competition between Bond Breaking and Bond Making

Dau

Gibson

2015

J. Phys. Chem. A

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Transfer of halogen atoms from halogenated acetate ligands, CX3CO2 (X = F, Cl, Br), to actinyls, AnO2(2+) (An = U, Np, Pu) is stimulated by collision-induced dissociation (CID) in a quadrupole ion trap. CID of [AnO2(CF3CO2)3](-) complexes results exclusively in F atom transfer, concomitant with elimination of CF2CO2, to produce [(CF3CO2)2AnO2F](-), [(CF3CO2)AnO2F2](-), and [AnO2F3](-). This contrasts with CID of transition metal fluoroacetates for which CO2-elimination to produce organometallics is an important pathway, a disparity that can be attributed to the differing bond dissociation energies (BDEs) of the created metal-carbon and metal-fluorine bonds. The dominant pathway for CID of [AnO2(CF3CO2)(CCl3CO2)(CBr3CO2)](-) is Br-atom transfer to produce [(CF3CO2)(CCl3CO2)AnO2Br](-). The preferential formation of bromides, despite that the BDEs of An-F bonds are substantially greater than those of An-Br bonds, is attributed to the offsetting effect of higher BDEs for C-F versus C-Br bonds. The results for the trihaloacetates are similar for uranyl, neptunyl and plutonyl, indicating that for all three the An-X bond dissociation energies are sufficiently high that X atom transfer is overwhelmingly dominant. CID of [UO2(CH2XCO2)2(CX3CO2)](-) (X = F, Cl, Br) resulted in F-transfer only from CH2XCO2, but Cl- and Br-transfer from both CH2XCO2 and CX3CO2, a manifestation of the characteristic increase in BDE[C-F] in CHx-nFn species as n increases; the overall thermochemistry determines the observed CID processes, providing clear distinctions between fluorides and chlorides/bromides. The results of this work reveal the propensity of the actinides to form strong bonds with halogens, and suggest that there is not a large variation in actinyl-halogen BDEs between uranyl, neptunyl, and plutonyl.

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Section: Introductionmentioning

confidence: 99%

Halide Abstraction from Halogenated Acetate Ligands by Actinyls: A Competition between Bond Breaking and Bond Making

Dau

Gibson

2015

J. Phys. Chem. A

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“…Much work has involved the immobilisation of waste uranium from nuclear fuel rods, either in its pure form, or within a bisorbent (Glasser and Atkins, 1994;Venkobachar et ah, 1995). Studies have examined both the uraniumcontaining -cement matrices and their interaction with the highly alkaline pore fluids (see, e.g., Linklater et ah, 1996;Altenheinhaese, et al, 1994;Amini et ah, 1993;Berner, 1992;Atkins et ah, 1995Atkins et ah, , 1988. Recently, the latter group has reported on the synthesis of materials in the system CaO-UO 3 -SiO 2 -H 2 O (Moroni and Glasser, 1995); in addition to the established mineral phases, a number of new phases were identified.…”

Section: Introductionmentioning

confidence: 99%

X-ray diffraction data for two new calcium uranium (VI) hydrates

1997

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The X-ray powder diffraction patterns for two new synthetic calcium uranium (VI) silicate hydrate phases are reported. Ca1.5U6(OH)7O16·7H2O is orthorhombic, space group P*a*, with unit cell a=13.8949(14), b=12.0776(12), c=15.228(3) Å. The structure appears to be related to that of becquerelite. Ca2(UO2)2(Si2O5)3·10H2O was also indexed on an orthorhombic unit cell, a=12.075(3), b=15.406(6), c=26.043(6) Å. The Powder Diffraction File coverage of uranium-containing minerals which could, on the basis of their chemical formula, form in U-containing cements is also reviewed.

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“… metal oxides (Plotnikov and Bannykh 1997c, b, a)  carbonate-rich sediments and minerals (Kaplan et al 1998;Carroll et al 1992;Carroll and Bruno 1991 ;Tait et al 2002;Kelly et al 2003)  iron-bearing minerals (Duff et al 2002 ;Rovira et al 2000)  aluminum oxide (Denecke et al 2003)  silicon dioxide (Prikryl et al 2001;Moroni and Glasser 1995)  cement-specific components such as calcium-silicate-hydrates (Kienzler et al 2001;Matzen et al 2000;Altenhein-Hasse et al 1994) and calcium-oxides (Moroni and Glasser 1995). Sutton et al (2003) suggested an apparent two-stage sorption mechanism attributed to surface complexation of uranium with siloxyl groups in grout.…”

Section: Introductionmentioning

confidence: 99%