TEM study of Green Rust Sodium Sulphate (GR(NA,SO4)) Interacted with Neptunyl Ions (NpO2+)

TY - JOUR

T1 - TEM study of Green Rust Sodium Sulphate (GR(NA,SO4)) Interacted with Neptunyl Ions (NpO2+)

AU - Bach, David

AU - Christiansen, Bo C.

AU - Schild, Dieter

AU - Geckeis, Horst

PY - 2014/4

Y1 - 2014/4

N2 - Green rust (GR) as sodium sulphate form, NaFe(II)6Fe(III) 3(OH)18(SO4)2 · 12H 2O, is reacted with an aqueous solution of neptunyl ions (NpO 2 +) and the resulting Np(IV) solid phase is investigated at a nanometer scale by different transmission electron microscopy (TEM) techniques, including high-resolution TEM (HRTEM), highangle annular dark-field scanning TEM (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDXS), and electron energy-loss spectroscopy (EELS). The aim of the analyses is to achieve insight into the potential immobilization mechanismforNp(V) in the context of safety assessment of a nuclear-waste repository. The neptunium is found to be immobilized at the edge of the green rust platelets, in a rim composed of nanocrystallites about 2-3.5 nmin size. The EELS results andmore particularly theHRTEMfindings are consistent with NpO2 crystallizing in a fluorite-type structure. Furthermore, the Np-O4,5 edges recorded by EELS at the Np(IV) phase are presented, expanding the EELS-data set currently available in the literature for Np.

AB - Green rust (GR) as sodium sulphate form, NaFe(II)6Fe(III) 3(OH)18(SO4)2 · 12H 2O, is reacted with an aqueous solution of neptunyl ions (NpO 2 +) and the resulting Np(IV) solid phase is investigated at a nanometer scale by different transmission electron microscopy (TEM) techniques, including high-resolution TEM (HRTEM), highangle annular dark-field scanning TEM (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDXS), and electron energy-loss spectroscopy (EELS). The aim of the analyses is to achieve insight into the potential immobilization mechanismforNp(V) in the context of safety assessment of a nuclear-waste repository. The neptunium is found to be immobilized at the edge of the green rust platelets, in a rim composed of nanocrystallites about 2-3.5 nmin size. The EELS results andmore particularly theHRTEMfindings are consistent with NpO2 crystallizing in a fluorite-type structure. Furthermore, the Np-O4,5 edges recorded by EELS at the Np(IV) phase are presented, expanding the EELS-data set currently available in the literature for Np.

U2 - 10.1515/ract-2013-2105

DO - 10.1515/ract-2013-2105

M3 - Journal article

SN - 0033-8230

VL - 102

SP - 279

EP - 289

JO - Radiochimica Acta

JF - Radiochimica Acta

IS - 4

ER -