@article{c11b0d49d8e44de2baa8c7c23aefc8f0,
title = "Speciation and ammonia-induced precipitation of neptunium and uranium ions",
abstract = "The pH evolution and corresponding changes in the UV-Vis-NIR absorption spectra of oxygenated neptunium (NpO 2 + and NpO 2 2+) and uranyl ions (UO 2 2+) in nitric acid are investigated during titration with an aqueous NH 3 solution. The speciation and precipitation regimes between acidic (pH 1.5) and alkaline (pH 10) conditions at room temperature are discussed to assess the suitability of Np(V) or Np(VI) in sol-gel conversion processes for fuel target fabrication. Under the applied experimental conditions, Np(V) hydrolyzes and precipitates into the insoluble hydroxide NpO 2OH only above pH values 7.5 and an increase up to pH 10.0 is required to precipitate quantitatively. Np(VI) displays changes in the coordination environment of NpO 2 2+ ions in the pH interval 1.6-4.0, similar to what is observed for U(VI). Precipitation into NpO 3·H 2O or other hydroxide compounds takes place between pH 4.0 and 5.9, which overlaps largely with precipitation of ammonium diuranate species from the U(VI) solution. The use of concentrated NH 3 aqueous solution, as commonly used in the external gelation process, will allow to quantitatively precipitate both Np(V) and Np(VI) species. Internal gelation process conditions, on the other hand, seem incompatible with the high pH required to precipitate Np(V) completely. For fabricating mixed-oxide (U,Np) targets using sol-gel conversion, a feed broth containing Np(VI) and U(VI) will be required to achieve homogeneous gelation.",
keywords = "Neptunium, Uranium, Hydrolysis, Precipitation, Sol-gel",
author = "Gregory Leinders and {Acevedo Mu{\~n}oz}, Beatriz and Fr{\'e}d{\'e}ric Jutier and Gamze {\c C}olak and Marc Verwerft",
note = "Score=10 Funding Information: The authors wish to thank K. Vanaken, P. Dries, and E. Kox for laboratory assistance, and the Radiochemical Analyses group of SCK CEN for performing the ICPMS analyses. The authors also thank A. Moens and G. Sibbens of JRC Geel for providing the NpO2 feed material that made this work possible. The research presented in this article has received funding from the European Union{\textquoteright}s Horizon 2020 Research and Innovation program under Grant Agreement No. 945077 (Project PATRICIA) and was carried out as part of the PULSAR project within the framework of the Euratom Research and Training Programme (Grant Agreement No. 101061251). Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or Euratom. Neither the European Union nor Euratom can be held responsible for them. Funding Information: The authors wish to thank K. Vanaken, P. Dries, and E. Kox for laboratory assistance, and the Radiochemical Analyses group of SCK CEN for performing the ICPMS analyses. The authors also thank A. Moens and G. Sibbens of JRC Geel for providing the NpO feed material that made this work possible. The research presented in this article has received funding from the European Union{\textquoteright}s Horizon 2020 Research and Innovation program under Grant Agreement No. 945077 (Project PATRICIA) and was carried out as part of the PULSAR project within the framework of the Euratom Research and Training Programme (Grant Agreement No. 101061251). Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or Euratom. Neither the European Union nor Euratom can be held responsible for them. 2 Publisher Copyright: {\textcopyright} 2023 American Chemical Society.",
year = "2023",
month = jun,
day = "26",
doi = "10.1021/acs.inorgchem.3c00647",
language = "English",
volume = "62",
pages = "9807--9817",
journal = "Inorganic Chemistry",
issn = "0020-1669",
publisher = "American Chemical Society",
number = "25",
}